# Gypsy Engine



## Flopearedmule

Hi 
I was wondering if anyone would be interested in buying Gypsy castings?  I had a set made for myself and the foundry has more made.   I bought the prints from John Chenery about 4 years ago, and he said he will sell the prints but not the castings.  I have tried to email John again, but he must have changed his email address.  If anyone knows how to contact him I would appreciate it.


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## gadabout

Yes, price?

Mark


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## aonemarine

What does it look like when completed??   Is be interested.


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## Mitchg07261995

im interested for sure


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## Flopearedmule

here is one I found by just doing a search on google


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## Flopearedmule

I will post the price when I find out.  I'm waiting for the foundry to call me back.
Thanks


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## LSEW

It looks like there is a fair amount of interest. I am also interested. You only show 2 castings, is that all there are? It would be nice to have the heads as well. Can you get another run at the foundry? Is this the engine sometimes called the Gypsy Moth? 

It looks like the crankcase has the same machining issues as the Coles Holt 75 engine. I am building 3 of those this winter, so I will be tooled up for it.

Thanks,
maury


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## nowramfg

I think the heads are barstock if memory serves me right. I did see, and may have the drawings for this, or one very similar. I also would be interested in some castings.


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## Flopearedmule

Still looking for John Chenery's email address or phone number.  Can anyone help me out here?  I don't think he would want me giving copy's of the blueprints to everyone.
Thanks


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## lantain1982

Regarding John Chenery`s email,   try,   [email protected]
I bought a set of prints from him in the last 6 months.
Cheers, lantain1982


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## Flopearedmule

lantain1982 said:


> Regarding John Chenery`s email,   try,   [email protected]
> I bought a set of prints from him in the last 6 months.
> Cheers, lantain1982



Thanks lantain,
I tried johnc-(at)msn(dot)com  is that what you meant?

Dennis


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## lantain1982

Hello  Dennis, sorry about the missing dot.     Hope you made the contact?.
Bill.


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## Flopearedmule

Ok everyone.  
John Chenery emailed me and said he will sell the prints for the Gypsy.  His email address is ....   johnc- (at) msn.com 
Then you can contact Abe at Keystone Pattern....keypat (at) mymts.net  and he is making the castings.  Good Luck


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## Buchanan

Hello

I have been watching this thread for a little while. I have a centrifugal caster with an induction coil to melt the metal. If sombody made a good patern i would give casting them a go. it would be a lost wax casting.
My maximum cast weight is about 150 grams in bronze.I have produced a few high detail castings in bronze and the machine works well.

Regards 

Deryck.


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## Flopearedmule

I just got my set in the mail today.  They are very detailed.  Abe really did a great job!  The original castings were all solid, lots of machining had to be done.  These even have detail on the inside.


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## thayer

Can we ask what the drawings and castings cost?


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## Buchanan

I am sorry but i should have made myself a little clearer. I was thinking of  casting the head and possablly the rockers, not anyof the castings that are available from others, but any of the small items that there are a few of. Aliminium is no problem and I should also be able to cast steel in up to 50 gram quantities.

Deryck


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## Flopearedmule

thayer said:


> Can we ask what the drawings and castings cost?




I paid $60 for my prints a few years ago.  Not sure how much Keystone Pattern is going to charge for castings.  You will have to email them and ask. 
This is an engine that was very popular with builders in the Strictly I.C. magazine.  When Les passed away you couldn't buy the castings anymore.  If you think you might build this engine some day, you better buy everything now before its too late.


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## Flopearedmule

Keystone Pattern just emailed me and said they can sell the castings for $300.  
Email Abe at ........keypat (at) mymts.net

Thanks
Dennis


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## aonemarine

Ouch!!  What material are they cast in and what is the weight of the castings?  Id like to see what the finished castings look like before making any decisions. That picture you posted was of the patterns??


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## thayer

The photos posted are of the castings. I got the same set when I enquired last week. I do not know the weight.

"The castings we have available at this time are the engine block and the oil sump only, as per attached photos. They are aluminum heat treated to 6061 T6 for better machining. The selling price is $300 plus shipping, which is about $25 to the USA.
Thanks for the interest."


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## Flopearedmule

aonemarine said:


> Ouch!!  What material are they cast in and what is the weight of the castings?  Id like to see what the finished castings look like before making any decisions. That picture you posted was of the patterns??




I don't think he is out of line for the price.  The castings are very good quality.  The picture I posted is the castings.  
There are a lot of steam, and gas engine casting kits out there that cost more.


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## aonemarine

Im a back yard foundry man, to me it seems like alot because I can make my own castings for just a few dollars. The time spent making the patterns is another story. My hat is off to the guy that made the patterns. Very nice and detailed work.


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## michael_au

Do you still have the castings, and ifso how much are they please

Thank you
Michael


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## Flopearedmule

michael_au said:


> Do you still have the castings, and ifso how much are they please
> 
> Thank you
> Michael




check post #13 on this thread.  the email address to buy prints and castings are on that post.


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## skyline1

Please excuse me butting in to the thread gents but is this a model of  the gypsy major engine as fitted To DeHavilland Moths and Chipmunks among others 

It sure looks like one, air cooled , 4cyl , 140 hp (the full size one) 

Or is it derived from one, as the Gypsy Major was an inverted four cylinder.  

I'm curious as I am an ex Air Cadet who flew in Chipmunks 

Regards Mark


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## Cogsy

I too once had the thrill of flying in both a Tiger Moth and a Chipmunk, although my first ever flight with 'hands on stick' was in a North American P-51 Mustang... The most exhilarating 45 mins of my life! 

P.S. This was in 2003 - not WW2...


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## gus

Cogsy said:


> I too once had the thrill of flying in both a Tiger Moth and a Chipmunk, although my first ever flight with 'hands on stick' was in a North American P-51 Mustang... The most exhilarating 45 mins of my life!
> 
> P.S. This was in 2003 - not WW2...



Hi Cogsy,

WW-2 in Oz.

My Aussie boss now 90 living in Bandanoon,nearby Sydney, was 18 year and trained to fly Spitfire .Soon after he got his wings and WW-2 was over.:wall: 
He was all set to dog fight and shoot down some Japs.
Made it a must to visit him every year and after every visit promise him I will visit him again next year. Was a good boss.He gave me a chance to rise up thru the ranks over 20 years and retired as Ops Manager.He made me work my guts off.


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## goldstar31

I'm Goldstar 31 which translates as Royal Air Force 31 Squadron and whose aircraft still carry the Star of India as their emblem. 
In my days -1948-50, we had Gypsies of all sorts. We had them in our Percival Proctors mks 3 , 4 and 5, we had them in as Gypsy Queen 71's in what was then the new DH Devons C1's which were actually Doves and as our adopted aircraft, those in  Austers of the  newly formed RAF Antarctic Flight. We sort of collected things on our little patch of green in the middle of London and had Air Observation Post Austers  of 661 Squadron and an assortment of Spitfires of 601 and 604 Squadrons before they flew away to get DH Vampires.

As for Spits, we were left with 3.  a RR Griffon, Rolls Royce Merlin and those bloody awful Merlin Packard things. Dear old SL-721 a Mk LF 16E is still airworthy whilst there is still a pair of Devons in RAF Cosford Museum. Old VP-981 is still airworthy but is now registered as a 'Civvy'. The last we heard of her was at John Lennon Airport waiting for an engine change- and then she flew away.
Johnny, my old mate used to mend the Gypsys which were notorious for oiling up- and one crashed on the Queens Birthday 21st April 1949 killing all 3 crew. 

So RAF 31 is still flying alongside the Tornados of 617 Dambusters -and all that jazz. 1915 is our Century  and with luck, we'll just make it.

Per Ardua Asbestos, Nil Illigitimi Carborundum from Cpl Atkinson, RAF ( Ret'd), WC and Chain, VD and Scar.


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## skyline1

Oh heck fellas I seem to have accidentally got something started here Gypsies, Merlins, Griffons, and even Packup & Witless (sorry guys ,bias showing, no slur intended but I am a Brit) all good Motors but I don't want to corrupt the OPs thread, so should I start a new one along the lines of "Favorite Aero Engine ?"

Regards Mark


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## goldstar31

It is perhaps a good idea to ramble a little about the 12 inches to the foot variety of things if only to get some concept about what the miniature version is all about.

With the hindsight of old age, none of you would be quite where you are now had it not been for the little Gypsy engine  and the men and  women who learned their trade on them. The Battle of Britain- and that is only one instance was won by men who had sat behind the little Gypsy not much earlier.


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## skyline1

Quite, well said Sir, amazing little engine which deserves to be celebrated.

It would make a splendid model, a tribute to an unsung hero, not just in times of war but peacetime too, and the many brave men and women who trained on them.

Regards Mark


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## Ringsnapper

The last post on this was about 8 years ago but I recently (3/21) purchased the Keystone castings for this engine as well as the drawings from John Chenery. The castings are still $300 USD. Only the top and bottom crankcase halves are available. I‘m in the process of casting (lost foam) the gear cover / oil pump housing / magneto carrier and the carburetor. The carb will be lost wax. 
I think the original kit also included a casting for the crank bearing caps and possibly the dummy magneto‘s that conceal the distributor and contact points.
The quality of the Keystone castings looks very good. I have not started any machining as yet though.


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## Ringsnapper

Not sure if this is of interest as it’s not machining, more pre machining, but here is some account of the the foam pattern for the oil pump housing/ cam gear housing etc. derived from the Chenery Gypsy drawings. The oil pump cover (with the figure 8 looking bit) is designed to be cut off the casting so is made overly thick. The pattern is a mixture of a thick housing with thin‘ish webbed ‘arms’ to support the ‘magnetos’ / distributor so there is some challenge in successfully casting this (at least for those of us not skilled in the art, this is my first try at foam casting… in case anybody thought I knew what I was doing !)



The first attempt was not a success as the metal did not reach the ends of the magneto support ‘arms’ before it cooled. This used a simple sprue arrangement into the top of the oil cover, you can see the remains of it here. No additional gating, so not really a big surprise I guess. I did use a vent at the other end of the pattern, but I will dispense with it next time, it’s just a heat loss. Lessons learned at least.



The second pattern attempt with a repositioned sprue more centrally placed and additional gating attached. I put a dog leg in the main feed sprue to try and reduce turbulence in the pour as there was evidence of ‘oxide folding’ in the first casting attempt. Probably only the gates to the arms are needed but this is all experimental anyway.


Last step is coating the pattern with a refractory (aka drywall mud) to improve the cast surface finish and leave to dry.


Anyway, fingers crossed for a second try.


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## MrMetric

Interested?  Are you kidding?  Count me in!  I think this is absolutely applicable to the hobby and is of high interest.  I love following threads like this.  Keep it coming.


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## skyline1

MrMetric said:


> Interested? Are you kidding? Count me in! I think this is absolutely applicable to the hobby and is of high interest. I love following threads like this. Keep it coming.



Me too


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## Ringsnapper

OK. Cool.  
I poured a casting of the revised pattern and as expected there was a good bit of improvement In the result. The webs of the magneto platforms  that caused premature cooling of the metal last time were completely filled this time around and it looks like all the pattern edges came out reasonably well.I think the sprue position was the chief factor here, the additional gates may have helped but at least one of them did not fill .  


With gates removed.


Here’s how the casting joins to the crankcase, it becomes the cover for the gearing from the crank up to the cam shaft. The piece I am holding is the oil pump. Just above that there is a housing for a shaft with a 90 degree helical gear. The secondary shaft then drives the dummy magnetos on the two horizontal armson either side for the distributor and points.
So there is a lot going on in this little casting !




I’ll keep this one but I‘m going to have one more shot at this. The issue is that there is quite a bit of pitting on the rear surface (just above my thumb) which will be very visible. I should have built the thickness of the pattern up here so it could be milled down to size. There are also a couple of bearing caps that fit on there as well so it was an obvious oversight not to allow for machining.
Third time lucky.

RS.


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## MrMetric

I'm no expert with casting... And, in fact, I'd say that you clearly know more than me.  However, even a nincompoop can sometimes help one remember forgotten steps.  To that end, I guess there are two questions I would have for you.   First, I assume you degassed the metal prior to your pour?  Second, what alloy are you pouring (where did you get your metal).  It looks like you've got quite a bit of porosity voids there, as you have noted.


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## Ringsnapper

Good Questions.
The metal used was from a scrap alloy car wheel.
l have done some sand casting in the past and have had better luck with cast alloys than extruded stuff like drinks cans and window frames etc.
I did not use degassing tablets in either of the pours and on the subject of gas and voids here is a cross section of the first casting.

This shows a couple of pockets that formed at the surface. One on the top edge and one in the middle of the photo. Plus a cloud of micro pores across surface.
Here is the top edge zoomed in.


These are relatively small in comparison to the much larger ‘craters’ on the surface maybe 3mm across in some cases. Most are a superficial depth but others are maybe 0.5mm deep.


Is this larger pitting gas voids from the metal or maybe some residual of the foam that fails to escape. If they were gas from the metal I would have thought the metal at the surface would have cooled far quicker than the interior metal and the voids would not have grown so large.

I‘m using quite fine sand that is packed by vibration. I’m wondering if the foam gas is not absorbing well into the sand because it is so fine and I should try a coarser sand with more permeability.
I’ll add that to the list.
Thanks

RS.


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## MrMetric

I have often wondered about how well the foam burns out or gets displaced.  So, you are definitely hitting an area that is a curiosity for me.... I'm more familiar with die casting than with any of the investment type of casting methodologies.  And even there, I grew up in that area (die) but never did it myself.  I went into electrical engineering instead of following the family tree.


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## skyline1

I'm by no means an expert on these things but I have done a fair bit of Aluminium casting in the past  so here are my thoughts, right or wrong (more experienced members should feel free to disagree it won't cause offence).

The "micropores"  in the picture do look like gas porosity and whilst in many cases these are not a problem, in this case, as we are talking about engine parts they could cause difficulty some degassing would improve matters.

As would an "active flux" which not only makes drossing off much easier, but actually refines your melt by actively drawing impurities out. The products I used were "Degasser 190 and "Coveral 11" respectively  both from Foseco limited in the U.K. You may not be able to get them in the States but I am sure there are suitable alternatives

The surface "craters" are a little more difficult to diagnose, As you say they could be residual products from the foam, but could equally be due to some kind of sand penetration from the mould, they could even be caused by steam if the moulds were at all damp,

I think the pouring temperature might be a little low as shown by the fact that some of the gates have not filled completely, and ideally you should provide a "riser" opposite the pouring sprue this keeps a "head" of metal to allow the casting to "draw" from and also provides extra exit for the gasses.

That all said these are good castings for a first attempt at this type of casting. I wish some of my first ones looked that good.

Best Regards Mark


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## master53yoda

I agree with what has been shared so far, entrained gases are normally pinholes under magnification through out the casting 
,normally remelting ingots releases the entrained gases.  My processing furnace is direct fired with the scrap in the flame, this does entrain gases, the degassing recipe below does solve the problem .

 I provide quality aluminum ingots from automotive engines, mostly to Hobby casters and a few small foundries and Galleries.   I've processed over 14 tons in the last 5 years,

That said I have had a number of customers ask  casting questions, so I started providing the following information in each box sold. 

I'm based in the US, so some of these ingredients maybe known by different names in other areas.   I also have a process for heat treating with a ceramic Kiln if any one would like that.

Art B


*Flux recipes*

Drossing Flux  (used in our processing)

50%    sodium chloride   “normal salt, preferably without Iodine)

50%    calcium chloride  “NoSalt brand”

One teaspoon per 10 -12 lbs.



Degassing and Drossing Flux   “*Caution releases chlorine gas, you must have adequate ventilation*”

50%  Drossing Flux 

50%  calcium hypochlorite    “Pool Shock”

One tablespoon or three teaspoon per 12 lbs.


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## Ringsnapper

The third attempt on the oil pump casting produced better results as far as the surface finish was concerned and I think this technique will be good enough. The patina is now essentially the finish on the foam pattern.



So this time round I coated the pattern with plaster. Not plaster of Paris but a metal casting version of it called HydroPerm. The main difference is there is more talc in it plus some Portland cement, not sure what else.
My theory from the previous attempt was that the joint compound had simply not been strong enough to stay together in the presence of all the violent off gassing of the foam etc. I think joint compound could still work but it needs to be applied very thick.
The problem with plaster is that the foam gas does not get out easily even using the modified stuff.


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## Ringsnapper

A better shot of the casting surface.


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## skyline1

Very impressive, well done !

With changes in section and some very awkward angles these are not easy castings to do but you seem to have the technique well worked out now.

I doubt a commercial foundry with extensive (and expensive) resources could do any better, If you could find one willing to take it on at a reasonable price.

This new capability brings your Gypsy project one step closer and I shall be following this thread with much interest.

Best Regards Mark


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## Ringsnapper

Thanks. I think the coating was definitely the answer to the surface finish issues of the previous attempts. To that I’ll add some rambling thoughts and learnings.
There are commercially available coatings specifically for this but they are only available in large quantity and are very expensive. I think these coatings (and joint compound) must micro fracture enough to allow the pressurized gas to escape into the sand but retain enough structural integrity to keep the surface finish.
The plaster obviously sets hard and does not let the gas escape, so if the casting is to be machined, drilled, tapped etc. then the potential for problems with gas voids is much greater.
Just my two cents but I think limiting the plaster use to only visible surfaces that are not machined and using JC ( or possibly nothing) everywhere else might be a good compromise. That said I am experimenting with a thicker more even JC coating as I just feel it’s the best solution for foam if it can be applied correctly.
 Any trapped gas bubbles are likely to occur near the top of the casting  so orienting  the pattern in the sand with the ‘void’ sensitive areas low down in the flask seems advisable (not what I did ). In this case the oil pump gallery. Also avoid large flat horizontal surfaces by tilting the pattern in the sand.
Vents certainly clear a lot of the initial gas envelope out of the pattern if it can’t get through to the sand but don’t guarantee that all the later bubbles will get out as the metal cools, particularly as this is occurring at the fast cooling surface of the casting. My worry about vents, other than this, is that it may be that the initial expansion of gas that fractures the coating and allows the gas to permeate the sand. So dissipating it through vents may not be what is wanted. Though clearly if the pattern is encased in plaster then this is the only option.
Anyway this Is an art and my hat is off and head bowed low to those that have mastered it, I’ll continue along the curve hopefully in a generally upward direction.

Rgds, RS.


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## skyline1

Whilst most of my casting was greensand I have done a little investment casting and as I understand it the coatings used are designed to be permeable enough to allow the escape of gasses but restrict metal penetration of the mould much in the same way as greensand does.

Just as with greensand, venting, especially at the uppermost points of the mould or where gas pockets might form is helpful and as you point out orientation can be important.

I would be interested in some more details about this HydroPerm casting plaster it certainly seems to be doing the job well, If it is the same sort of stuff I think it is then your micro-fractures idea is fairly close, It partially decomposes at casting temperature and forms a sort of matrix which lets the gasses escape.

Here is an old idea from greensand practice which may or may not work but might be worth a try. What about powdered graphite to improve surface finish, traditionally used for Cast Iron but I have used it with Aluminium with good results. It is traditionally mixed with Alcohol or a suitable solvent, sprayed on the mould cavity then either ignited or simply allowed to evaporate. If you can find a suitable solvent that doesn't melt your casting foam a quick spray on your pattern and allow it to evaporate before coating could be beneficial.

In any case I don't think you have a problem with surface finish anymore these castings look fine, the acid test will be machining them of course but you are definitely going in an upward direction so keep at it.

The cylinder heads look pretty tricky are you going to cast them or machine them from solid

Best Regards Mark


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## byawor

That is an intersting approach looks like it turned out ok.  Attached picture is my attempt made from the solid on mill.  I have the original casting but I figure getting the distributor drive gears to mesh is going to be trickey better to have a spare. I could never figure how to drill through that elbow for the in and out on the pump. I made the replacement without the elbows figuring to make them seperately.
Bob


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## Ringsnapper

That looks great, there‘s a good bit of machining and fitting on that part so doing a trial run is definitely the way to go. I‘m planning on making two casts just in case. 
I’ve had a bench mill on order from Taiwan for four months so I’m using the time to work on these castings.
Since the last attempt shown above I’ve done one other casting. It turned out that the longer of the magneto supports shrank by 50 thou and the shorter about 15 thou after the metal cooled so I
adjusted for that in the pattern.


Also on this attempt I went back to drywall compound as the refractory investment and the surface finish was a big improvement on the earlier attempt. The two big mistakes I think I made previously were to overheat the metal and I did not get enough of the residual moisture out of the cast plaster pouring cup. 
The Hydroperm plaster coated version looked good because it did not disintegrate with the excess moisture and heat but I don’t think it is as permeable as the joint compound. So in my case the Hydroperm seemed to be the answer but it was basically because I was doing other things wrong.
After machining and polishing the latest casting there is evidence of porosity in the metal still. I think you can see it in the photo.  I solicited some suggestions from experienced  lost foam casting folks on another forum and I think I need to reduce the metal temp some more (to 1400-1450 F) and also change the pouring arrangement to include a fill basin and weir into the sprue to eliminate drawing air into the metal during the pour.
Just waiting on a new thermocouple temp sensor  and I will try these things and report back.

Regards, RS.


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## Ringsnapper

First go at casting the crankshaft bearing end caps.


Lost foam cast also. The center cap has been experimentally milled fairly close to drawing dimensions but still a little oversized, the others are as they came out of the sand.
I think the porosity is a bit more under control now.
These end caps were poured at 1450 F using a pouring cup of Kelly Coffield’s design. Made from moldable ceramic fiber over a foam pattern, I would highly recommend using something like this for lost foam as it greatly reduces air entrapment. 



It can be used many times as molten aluminum does not wet it. It’s also a high thermal insulator.
The latest installment (#5) in the long saga of the oil pump housing casting shown below.


I realized as I assembled this foam pattern that I had not allowed clearance for the numerous studs and nuts around the periphery of the cam gear housing to the ‘magneto’ housings so I added 0.2 inch to the width. It’s in the drawings, I just missed seeing it before. 
After filing off the gates and cleaning up some areas with a file I have not encountered any of the dreaded gas bubbles of previous attempts but I’ll see how it goes. 
It’s tempting when seeing progress to keep trying to make it better with ‘one more go’ but I want to move on to the carburetor.


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## johnmcc69

Nice work!

 John


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## byawor

Chenerys original castings never left much room for error.  I screwed up  boring the main bearings I will show my "fix" if any interest. I remember asking Les how he did it he said no problem just use a boring bar. I tried but had no luck. Also boring for the cam shaft is very tricky.
Bob


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## Ringsnapper

Oh, yes please, I was wondering about that. I had seen a boring head being used for a  1/4 scale Cirrus build but it’s quite a different arrangement with only one centre bearing so plenty of room to get a boring head in there.


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## byawor

When I first tried holding it vertical and drilling just did not work well. Thought about mounting on the lathe carriage with boring bar between centers but dismissed that. Anyway with the screwing around the bores were not straight etc. Thought about buying a new casting but found Hemingway too difficult to deal with.  So to salvage the block I made a jig plate to locate bore centers and cut away the damaged stuff. Then I made new inserts, bored them undersize split and and secured in the block. Then I reamed them with a long reamer. Made mains again a little undersize mounted and reamed to size. Looks good but have not tried a trial fit with crank.


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## byawor

picture


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## Ringsnapper

Well saved ! What caused the original misalignment, the vertical drilling ?


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## Ringsnapper

The carb was the last item on the casting list and proved to be more of a challenge than anticipated (of course), mostly due to how many attempts at lost foam casting I stubbornly attempted.
This was probably the closest I got with foam, and possibly a light sandblast might have made it OK but I was struggling with porosity issues despite controlling the temperature and being careful with the pour.


In the end I drew the part up in fusion360, printed a resin pattern, pulled out the bucket of green sand and got to work. Just needed to remember to taper the fuel inlet pipe under the bowl so it lifts out of the sand cleanly. 
 I added a tang for holding the part in the chuck to facilitate machining of the conical intake mouth and drill the air passage.


This was the third try. It’s not perfect but it’s good enough for me and I can move on to other parts I think. 
I've been waiting for a mill to arrive which it has just done so. The plan is to start roughing the crankshaft from a piece of 1040 flat bar.

Regards


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## Ringsnapper

Getting the mill set up took forever but the DRO is on. Had to make custom brackets for the read heads as none of the supplied brackets worked out very well. Its finally all trammed in.

The crankshaft starting material was flat bar 9x2x3/4. It was fly cut to thickness and end milled to width. Then put in the four jaw and the ends faced and center drilled on the lathe. The block was then back in the mill to start the roughing out.



Ending up with all the cutouts.


Next job was to fabricate a lathe dog for turning between centers. I made this from some 1/4 in ms plate and scraps I found around the shop.


 To minimize distortion during turning I plan to make some steel spacers out of 3/4 in bar stock to fit between the webs. 

Regards.


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## Ringsnapper

About now someone shouts “Did you even look at the drawing before you started cutting metal !”
So the dimension from the tip of the front of the crank to the first crank web is shown as 1.987“ in the rough machining drawing. In the detailed finished drawing the same dimension totals as 2.05”. Ruh row. It’s not clear where the additional 0.063“ came from.  


 The finished drawing specifies the tapered portion of the shaft as 0.625”  plus a threaded portion of 0.25”. (The actual length of the threaded portion on the drawing however is less than 0.2”). My inclination is to shorten the tapered portion to 0.562”. Maybe the numbers got swapped around. Then it all adds up.
Possibly someone else has seen this and knows the answer or did something differently. 

Regards


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## Clive Brooker

Ringsnapper,

When I made the crank for my Gypsy, I also noticed some issues with the crank drawing. The attached sketch shows my own interpretation of the dimensions. Here, the original dims have been converted directly to metric. In order to get a 3 degree taper, the length of the taper needs to be adjusted  (15.17mm or 0.597ins). The dimension from the front of the crank to the first crank web is (here anyway) 51.37mm (2.022 ins) and there is a 40.46mm (1.593ins) dimension between the taper and the centre of the first crankpin.

In the end I actually decided to use a different angle for the taper and a longer screwed section. The crank turned out fine and fits in the crankcase bearings perfectly so I must have done something correct. I'm still someway from completing the whole project though!

Hope this helps.

Clive


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## Ringsnapper

Thanks,  yes, I see you checked the dimensions on the main drawing and accounted for it. I did notice that the taper angle was a bit shy of 6 deg with a taper length of 0.625”. Just to add to the fun the  prop boss that sits on the taper is drawn as 0.538”. If you add the 0.063” discrepancy to that you get 0.601” which is magically the exact taper length to get 6 deg. Does make you wonder..
Anyway, I will make the taper length 0.562” and use some other angle (like 6.4 deg) to make it work.

Regards,


----------



## Ringsnapper

A little further down the path with the crank shaft after a fair amount of time at the lathe knocking the corners off. There are a lot of oil ways to drill yet.



Before completing the crank I want to make a start on the top case. Skim the flange flat and mill the bearing supports to size. 
Something I noticed on the casting is there appears to be some shrinkage in the casting front bearing support. On one side it looks to have dropped about 1/16th” below the flange. 


I’ll see how it goes, maybe it’s Ok.


----------



## Peter Twissell

If the casting is a problem, i.e. it doesn't clean up, you could build it up with Technoweld, Lumiweld or similar antimony based aluminium 'brazing' rods.
I've used these rods over several years, mostly on motorcycle parts, with great success.


----------



## Richard Hed

Peter Twissell said:


> If the casting is a problem, i.e. it doesn't clean up, you could build it up with Technoweld, Lumiweld or similar antimony based aluminium 'brazing' rods.
> I've used these rods over several years, mostly on motorcycle parts, with great success.


What method of welding do you use?


----------



## Peter Twissell

The antimony based rods aren't really welding, more like brazing.
I use a propane torch for heating.


----------



## Weldsol

Peter Twissell said:


> The antimony based rods aren't really welding, more like brazing.
> I use a propane torch for heating.


The only problem in using those type of rods is that it is almost impossible to do any future TIG welding without removing all traces of it in close proximity.
Paul


----------



## Peter Twissell

I wasn't aware of that, thanks Paul.
In this case, I presume there is no plan to carry out any TIG welding on the crankcase casting.


----------



## Ringsnapper

OK, I skimmed the flange of the upper crankcase and as expected there is an area of the front main bearing support that remains below the level of the flange.


There is still maybe 0.02“ that could be removed but the depression is a good bit deeper than that. As kindly mentioned above this could be filled in relatively easily.
Having stared at this casting for a while and having looked at pictures of the original casting, as well as the drawings it became apparent that there are some significant differences which I think are worth noting.
The big difference is in the bearing supports. 


The three central bearing supports in the new casting consist of semi circular  sections supported by webs across the case. The front bearing support is a semi circular section that cantilevers out from the front of the casting. There is no material or webbing underneath it for either support or to accommodate  the cap screws.
For comparison here is a photo of the ‘original‘ Chenery casting at a similar stage of the build.


Notably, the bearing supports extend right down to the ‘top’ of the casting and the webs are a good bit wider. The front bearing is basically solid. There is plenty of material and depth for the bearing cap screw holes to be drilled into. I’m not sure the same can said for the new casting.
There are some differences on the rear of the casting. Here is the new casting and the original below.





There are two ‘buttresses’ on the right side of the original casting below the flange to hold two studs. The studs are not on the casting but you can see the tapped holes for them. These buttresses are missing from the new casting. 
Also the flange on the left side is thicker and joins to the cam gear housing to provide material for the two studs on that side. 
In contrast the flange on the new casting is oddly much thinner in this area and does not meet up with the gear housing until much further towards the center, with very little material for robustly securing the studs.
I’d be very interested in hearing from anyone who has built an engine with this casting to hear how they worked around these differences.

Note: The ‘original’ casting photos are borrowed from a really excellent thread on the Model Engineer forum by David K.


Regards.


----------



## Peter Twissell

Sorry to read of your casting woes.
I have used the aforementioned aluminium 'brazing' rods to add a lug to a casting (motorcycle gearbox) which was then drilled and tapped and has supported the clutch cable loads for over 10 years use.


----------



## Ringsnapper

Thanks, yes, I’ve used those rods once before to fill and re drill a misaligned threaded hole on a previous engine. The brazed metal seemed much harder than the cast aluminum and took the thread far better. 
I’d definitely consider that to possibly fix the stud issues at the rear.

My chief concern are the crank cap screws on the front bearing. Based on the drawing dimensions and some measurements they would be breaking out of the underside of the casting after a depth of 0.275”. They need at minimum a depth of 0.438” so they would be fully threaded for only about 60% of their length.
I wondered about over sizing the holes for these screws then try brazing some plugs in long enough to take the screws. What could possibly go wrong !

The webs would help on the other bearings, they are 0.17“ wide and the screws threads are 4 BA so drilled for 0.118”. 
   The problem here is that there are supposed to be oil ways passing to the bearing shells from one side of the flange through the web.  I’d guess that’s why Les made the webs as wide as he did on his own casting to allow for room to get a drill past the cap screws.
In fact due to the novel front bearing support arrangement it’s not going to be easy to get an oil way to the front bearing shell. Maybe a tube to cross the gap….

This casting has the feel of a prototype that hasn’t had the bugs taken out yet. I’ll probably find a shaft passing through the spoke of gear wheel next.



Regards.


----------



## Ringsnapper

By way of an update on the Gypsy castings. 
I contacted the originating foundry to ask if it was possible to modify the patterns and try another run. It’s been about 10 years since the original casting so I was not overly hopeful but they did reply and asked for details on the modifications, which I have passed along to them. 
I had hoped that only the upper crankcase casting needed rework but there are issues with the sump as well. 
Anyway, I await their response and quote for the work.

Regards,


----------



## Clive Brooker

Your casting looks similar to the Hemingway casting that I have (pictured). There is insufficient meat on the casting to drill the oil holes for the two end bearings. However, I'll only ever run the engine for short periods (if I ever get it to run) and I'll rely on enough splash cooling for those two bearings.

Clive


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## Ringsnapper

Thats interesting, I didn’t know Hemingway ever sold the Gypsy castings. I built the Aero V twin from them.
I wonder if they also tried to recreate them from the drawings and got similar results.


----------



## Clive Brooker

Hemingways don't list the Gypsy on their website but supplied a set of three castings to me as a special order about 18 months ago. The castings are fairly good in themselves but there are some simplifications/omissions in the patterns - no showstoppers though. If anyone's interested I'll post a summary.

I really liked your Aero V twin - must finish mine someday.

Clive


----------



## Ringsnapper

Spent some time recently preparing an attempt at a home casting of the upper gypsy crankcase. The first step was to modify the original casting to avoid the external feature issues.


I filled in some areas at the rear of the casting and blocked up the holes for the cylinders, leaving them slighty raised so that their positions could be located in the sand impression. I will use these to help locate the cores.
After a trial packing of sand and a few modifications I could lift it out of the packed sand without trouble.

I have also milled the sides of the lower crankcase casting. I was not hopeful that the flanges for bolting through to the upper case would be wide enough to allow clearance for the bolt heads, but it turned out it was OK They obviously built in a generous cross sectional taper to allow for the removal of the mold. 


I’m glad because it’s a really nice quality casting.


----------



## Ringsnapper

The top case requires four cores.


The middle two are identical but there are some differences in the two end ‘bays‘. Notably there is an undercut to the front crank bearing housing on the right that the oil fill passage connects to from above.
The pattern shown above  is based on the original casting with a lot modifications involving jb weld epoxy and pieces of wood. So this represents what I’m aiming for with the interior of the new casting.

I built two core boxes. One is for the rear core only, the second, shown below, can be used with alternate parts to make either the two center cores or the front core.


J

As shown the scheme to produce the cores involves a number of fitted pieces of wood that can be assembled using screws, then packed with sodium silicate impregnated sand, and then disassembled without putting stress on the cores. The core can easily be broken so the core molds were designed so that each section contacted a minimal number of sides.

Filled with sand.

Some additional notes on the core making….
Even with these  core boxes there was still problems with the sand sticking in the molds and breaking. Sodium silicate sticks to pretty much everything ! Success was eventually achieved by coating the interior surfaces of the box sections with a low viscosity epoxy resin. Epoxy is possibly the only thing the sodium silicate will not attack. I also rub carnauba wax onto the mold surfaces just for good measure.
I found that the sand needed to be thoroughly wetted through with the sodium silicate or the cores ended up too delicate to use, but maybe my sand was just coarse. Sieved play sand from HD.
After packing the molds with SS sand I placed them in a ziplock bag which was then filled with CO2.
Initially the CO2 was produced using vinegar and baking soda. I would place a 1/2 filled cup of baking soda in the bag and add vinegar through a tube, just enough at a time to get a reaction that came up to the top of the cup. This technique worked well and is very cheap. If time isn’t an issue you can just leave the cores in the mold and they will harden up just from the regular atmosphere after a few days.
I ended up making quite a lot of cores at the time as I debugged my core making process and eventually I bought a 0.6 L cylinder of co2 plus a valve. These cylinders are meant for carbonated drink makers. You can get a filled cylinder for $15 plus shipping, it’s ten times the expense of vinegar. You can fill a large zip lock bag about 50 times I found.

So with sand cores to hand, here is the sand casting plan of attack!

Step 1. Press a plywood template of the crankcase outline into the sand. The underside of the template includes indents to position the four cores.


----------



## Ringsnapper

Step 2. Place the crankcase pattern into the impression in the sand.


Step 3. Pack the sand around the pattern with sprue and vent. Separate the two halves of the mold , pull out the crankcase pattern and place the cores in position using the indents from the step 1 template.

.

Check the core positioning using another template for the cylinder positions.



Step 5. Figure out how much aluminum this is going to take and realize you need a larger crucible. 
Step 6. Realize the larger crucible won’t fit in your furnace.
Step 7. Build a larger furnace…….. sigh.


----------



## GreenTwin

This is one of the more confusing threads I have ever read, but none the less very interesting.
Someone named "floppyearedmule" (LOL) started this thread, and then 8 years later ringsnapper picked it up again, with all sorts of other folks apparently doing parallel builds, popping in randomly ?

After a quick read, I have a few comments, as follows:

1. I have followed numerous backyard "lost foam" casting projects, and so I researched lost foam castings (but have not done them myself).
The commercial foundries use polystyrene beads that are expanded into a metal mold via heating/steam.
The coating on the foam pattern has to be permeable enough to pass both liquids from the melting foam, and gas produced by the vaporizing foam.
The defects I have seen in backyard lost foam castings seem to be mainly due to using foam that is not polystyrene (rigid foam so that it can be machined), and perhaps from using a coating that is not appropriately permeable.
If the wrong foam is used, it may produce so much liquid and gas that it won't work regardless of the coating.

2. One guy showed me some lost foam castings, and he did not use any coating on the foam at all, and the castings turned out quite decent.
He just packed the foam in sand.

3. I experimented with sodium silicate cores, and learned what not to do.
I found that 3-4% of sodium silicate is all you need, and any more than that makes the core very difficult to break out after casting.
And putting a sodium silicate core in a bag with CO2 destroys it, which is why many people jack up the percentage of sodium silicate very high.
Sodium silicate sand should be gassed for 5 seconds only, and then no more CO2.
The SS cores I made and put into ziplock bags lasted less than a day on the shelf, regardless of SS percentage.
The SS cores I made at 4% with 5 seconds of CO2 have sat on the shelf and been perfectly usable after a year, and break out easily after casting.

4. Overheating aluminum causes all sorts of defects, such as porosity, and bad surface finish.
I heat my aluminum (356) as fast as possible to pour temperature (which is 1350 F), and then pour immediately.
Never stir aluminum; just skim and pour immediately.  I don't use a degasser, and don't need one the way I do it.
1350 F is gererally hot enough to fill most mold cavities, and cool enough to give a smooth surface finish, especially in Petrobond.

5. I would probably bake those cores to be sure to drive off all moisture; perhaps at 250 F?
I generally lightly flame my cores with a gentle propane flame, to do the same.

6. I generally use a runner down the side of thin parts like that, with several gates.
Thin parts seem to fill better with knife gates, which are wider gates with fill the mold faster.

7. I have had molds like that trap air, and ruin the casting with a large air bubble in the casting.
I have since started venting the high points of the mold with small holes poked with a wire.

8. And the best way I have found to stop ss sand from sticking to a corebox (ss sand is very bad about sticking) is to apply blue painter's tape to the interior surface, and then apply a little Johnson's paste wax to the tape every time before you make a core.
There is not much that will stick to 3M blue painter's tape.

These are a few things I have discovered over the years.

Great thread whoever is posting on it !!!
I must say that floppyearedmule wins the prize for best screen name though.
.


----------



## johnmcc69

Excellent work!

 John


----------



## GreenTwin

And one last trick, if you need a larger crucible, and it won't fit into your furnace, stack hard fire bricks around the top, and temporarily extend the height of the furnace (assuming the diameter is ok).

You can use a pottery shelf as a temporary lid.

This is just hard fire bricks banded together.
You can make a new furnace in about 30 minutes, for aluminum use.
Not pretty, but functional.


----------



## Ringsnapper

Thanks GreenTwin, very interesting comment on the CO2 exposure time. I started out worrying that the gas wouldn’t get into the cores enough and left them in the bag for hours. Then wondered why they fell apart under their own weight. Since then I’ve generally not been as concerned about the exposure time  but was definitely using a wetter mix, so I‘ll scale the mixture back on the next batch and see how it goes with just a whiff of gas.


Anyway, thanks again, when I get the larger crucible I’ll put together a furnace as you suggest.


----------



## Ringsnapper

So just by way of an update to the Gypsy casting saga.
I have increased the amount of aluminum I can melt to about 6lbs which is more than enough for this casting.
At this point I‘ve had  four goes at it.
In the first one, shown below, there were some areas the metal did not completely flow. The mold was pretty thin in those areas and possibly that plus moisture/ steam out of the cores stopped it flowing. I post it as the failures can be enlightening or entertaining at the very least.





This first one was cast in petrobond but the later attempts were done in homebrew green sand ( play sand sieved to through #50 mesh with about 15% bentonite clay by weight ), so pretty rough stuff in comparison to the petrobond. I figured there would be a number of trials to get things sorted out and green sand Is cheap and easy to re mull in comparison. If I could get my hands on some finer silica sand locally I’d stick to green sand. Petrobond does give a nice finish but it’s messy and expensive.
After this attempt I shrank the width of the cores by 2 mm on each side and didn’t have any further issues with run out in these areas. 
The next two later castings were plagued by, as it turns out, core moisture. I don’t have photos of those but the top of the castings looked like Swiss cheese and internally there was evidence of gas pocket formation. I should have realized what was going on sooner, particularly from earlier comments…

On the fourth attempt I baked the cores at 400F for an hour just prior to inserting them into the mold.




That did the trick, I just wasn’t getting the cores dry enough. This was something Green Twin mentioned earlier so thanks for that tip. The weather has also been extremely humid lately so leaving the cores on a shelf for days before a casting session probably wasn’t a wise move.
After some light skimming of the casting the metal appears to be generally good porosity wise. I used a 160 mm length sprue, 8mm in dia at the bottom and 16mm at the top, with a pouring basin. This arrangement was easy to keep filled throughout the pour. 
The metal itself came from eBay ingots so who knows what it actually is. 
The surface finish is quite rough, but it’s homebrew sand so not unexpected. Also the pour temp was higher than usual. It was at 1475F  when the crucible came out of furnace so probably 1450 by the time it got transferred to the pouring holder and actually poured. That’s higher than recommended.
I added a riser shown below at the front of the casting as there is a lot of solid metal in the front main bearing support. The original professional casting had bad shrinkage issues in this area.


In future castings I‘ll also add a riser to the rear end of the casting as there is a lot of metal in the cam gear housing and there was shrinkage evident there, though not critical it looks like a bottom rear corner of the casting got pulled up slightly, shown below.


The plan is to continue machining this casting, drill the crank  and cam bearings, the cylinder bores etc. and just make sure that the internal dimensions are basically OK and things line up.
 I think the issues of the original casting with the crank supports, oil ways, and the flange for the bolts to hold the sump are addressed but I want to make sure there isn’t anything else lurking.
If everything checks out on this one I’ll do a casting in oil sand to improve the surface finish.

Best Regards,
RS.


----------



## byawor

You have more patience than I could muster.  Just my experience with the original castings.  When i bored for the cam shaft it came through at the front. Looking at it I think there was not enough metal there. A guy I know also had the same experience so maybe check it out 
Bob


----------



## MrMetric

Patience indeed, but very interesting.  It reminds me of die casting, something my family was heavily involved in... I'm curious what type of aluminum you are using.  I know we used 356 as one of the dominant alloys in die casting, but I'd be hard pressed to say what benefits it has over other types. And bear in mind that those benefits may only be applicable to the aluminum being forced into a steel cavity at great speed through the use of a high pressure ram.  Investment casting is a different beast.


----------



## GreenTwin

From this source:


			https://materialsdata.nist.gov/bitstream/handle/11115/173/Aluminum%20and%20Aluminum%20Alloys%20Davis.pdf
		


_Casting co__mpositions are described by a three-digit system followed by a
decimal  value.  The  decimal  .0  in  all  cases  pertains  to  casting  alloy  limits.
Decimals .1, and .2 concern ingot compositions, which after melting and pro-
cessing  should  result  in  chemistries  conforming  to  casting  specification
requirements. Alloy families for casting compositions include the f__ollowing:

•__ 1 xx.x: Controlled unalloyed (pure) compositions, especially for rotor
manufacture
• 2 xx.x: Alloys in which copper is the principal alloying element. Other
alloying elements may be specified._
_• 3 xx.x: Alloys  in  which  silicon  is  the  principal  alloying  element. The
other alloying elements such as copper and magnesium are specified.
The  3xx.x series  comprises  nearly  90%  of  all  shaped  castings  pro-
duced._
_• 4 xx.x: Alloys in which silicon is the principal alloying element.
• 5 xx.x: Alloys in which magnesium is the principal alloying element.
• 6 xx.x: Unused
• 7 xx.x: Alloys  in  which  zinc  is  the  principal  alloying  element.  Other
alloying elements such as copper and magnesium may be specified.
• 8 xx.x: Alloys in which tin is the principal alloying element.
• 9 xx.x: Unused_
_Heat-treatable __casting alloys include the 2xx, __3xx,__ and 7xx __series.

._


----------



## GreenTwin

Nice casting and molding work.
You are getting there.

.


----------



## Ringsnapper

I bored out the casting for the cylinders and right off the bat hit a snag. The new casting shrank in length by 0.075” overall with each of the cylinders about 0.025” closer together. So on a fixed 1.6 inch spacing on centers they become misaligned with the raised cylinder seat features on the top of the casting.


The rear cylinder only just fits on without breaking through the rear wall. Well this was the reason to keep going with this rough casting, to find this stuff out.



A bit of a cluge but I‘ll modify the existing pattern by adding 0.025” spacers between the cylinders for the next attempt. 


I also made a new pattern for the bearing caps I need before I can drill for the crankshaft. For some reason I hadn’t realized the bolts are only 4BA ! (I’ll use 6-32 UNF) and I had made the bolt head seats far too large, they would have looked ridiculous, not that anyone would see them….


I find it hard to visualize this stuff until I start getting parts together. The drawings assume you have all the castings so there are very few dimensions to go on.
Regards,
RS.


----------



## stevehuckss396

Are you going to machine the casting complete before casting another. Never know what else will pop up. This is interesting to me. Thanks for taking the time to take pictures and share them here.


----------



## Ringsnapper

Yes, that’s the plan. I’d like to get the crankshaft bearings drilled as well as the camshaft. Then I can mock up the gearing at the rear of the engine and check the gear housing for clearances etc. Obviously the crankcase casting shrank in width as well as length, I measured it as about 0.035”, so that needs to be accounted for.  I’m not intending to alter the pattern for this, I’m hoping it can be accommodated into the existing arrangement. Anyway we shall find out…

I cast the crankshaft bearing end caps today from the new pattern. My first attempt at this resulted in some shrinkage along the top of the casting so I added a 1” dia. riser about half way along the pattern and that fixed the issue. 
It’s amazing to see the metal collapse down the riser after the pour.


Regards,
RS.


----------



## Ringsnapper

l worked on the ‘shrunk‘ casting a little more and drilled through for the cam shaft. 
   All seemed well but I realized the foundry that produced the original casting I am now using as a pattern made the gear housing dimensions exactly to the drawing dimensions. This means I need to enlarge them, widen it essentially, to compensate for the shrinkage.
I decided to just make the cam gear housing wide enough to machine down as required to match my oil pump housing assembly ( another saga pages back) rather than attempt to ‘size’ it to the drawing dimensions. I think Les Chenery may have done something similar on his original design but not sure.
So with the length of the casting extended overall by 75 thou and some general enlargement of the cam gear housing I had another shot at it.


This shows the latest sprue , gate and riser arrangement. On all previous casting attempts there was quite severe shrinkage in the cam gear housing at the rear of the engine ( left side of photo) . I found that gating the riser only to the bottom of the casting was not effective enough, so after the cope was rammed up I broke the sand out between the riser and pattern almost up to the height of the pattern to allow the riser metal to reach further up. That seemed to work better though there was still a little shrinkage in that region. Maybe a bigger riser is needed. 
After quite a bit of machining of this casting I have seen very little sign of porosity so I think the sprue arrangement is working well.
 After boring out the resulting casting for the cylinders I was relieved to find the modification to lengthen the pattern was pretty much spot on with the cylinder bores on 1.6 inch centers.


The flanges for the cam gear cover / oil pump assembly are large enough now. 
Milling out the crankshaft bearing supports here. The webs line up well with the oil feeds on the side of the engine and most importantly it is possible to drill the oil feed to the front bearing. This was a big problem with the original casting.


Fitting the crank bearing caps.


Well l‘m keeping fingers crossed but I’m hopeful this is the final iteration. My small workspace is beginning to fill up with prototype Gypsy castings !

Regards,
RS.


----------



## Ringsnapper

As it turned out there was an issue with my ‘final‘ casting which meant another go at it. The tenth try.
 The bore for the crank shaft is 0.625” and is counter bored to 0.875” at both ends. At the front bearing the counter bore extends 0.375” into the casting. I had not allowed enough depth in the casting here, it’s hollow above the main bearing for the oil breather or filler, and the counter bore broke through into the cavity.
But number ten is progressing.


I started by machining the lower surface with a fly cutter. The goal is to get the height of the casting to 2”, so once I have the lower surface machined flat I flip the casting over and machine the top where the cylinders mount. Lots of checking on the surface table that the top and bottom surfaces are parallel. Then keep removing metal off the underside until the height dimension is achieved. 
My next operation was the bores for the cylinders. The casting pattern was made longer to accommodate shrinkage and its close but actually a little too long. It’s barely noticeable but to keep it that way I bored the number 2 cylinder first and then used that as the datum for the other three, they being 1.6” apart.


So then the the front of the casting needs to be 1“ forward of the rim of the front cylinder bore. Front of casting milled down accordingly.
This front surface and it’s relationship to the cylinders is very important because it’s the datum used for the position of all the crank bearing supports. 
The crank bearing mounts were milled to required widths. The rear of the casting was also machined down to the required overall length at this point (which is what the oil pump assembly attaches to).
At this point I made up the crank bearing caps from a previously shown casting and drilled them for the bolts.
The drawings spec the bolts as 4BA which I translated to 6-40 UNF And made a bunch of them from SS.
Drilled and tapped the casting for the bearing caps…. and disaster!. I was sooo careful. Had bought new taps etc. but the tap wrench I used managed to jam in the vertical axis and I stripped the thread on one hole.
I thought about just re threading a size up but in the end opted to try one of these low temp aluminum brazing rods. Fill and re drill.
The trick to success with using this stuff on castings is to get the casting hot enough overall so that you can melt the rod by playing a flame from a gas torch over the area. These rods melt at about 650F so well below the melting point of the casting but the casting will wick away heat very effectively. In fact the instructions that came with rods warn that an oxy acetylene torch is required on castings. Instead I heated the casting to 500F and then used a propane torch to get the localized area up to the melting point of the rod. I had drilled out the original threaded hole to something larger. You need to be sure the rod is melting into the bottom of the hole properly.
The operation went well and I re drilled and tapped the hole. Back in business! The caps were bolted down with 0.02“ shims in place.
At this point I was ready to drill for the crankshaft. On the mill I bored the front and back of the casting 0.875” dia to required depths. This is where things went wrong on the last casting.
I considered drilling the crank bore on the mill but in trying to set it up it just felt too awkward so I opted for the lathe.


I made up a bracket to support the casting on the saddle out of 3/16 angle iron. The holes were all slotted so it could be adjusted for height etc. The casting is secured to the bracket using three 
M6 bolts through the cylinder apertures. There are packing pieces made up to fit in the casting for the bolts to screw down on.
 I made up some 0.875” dia blanks to fit the end counter bores that were held in the chuck and tailstock to assist with alignment. Also a dial indicator to ensure the casting was horizontal.


I had made a 1/2 “ on center boring bar intending to get to final dia with it, but chickened out and went with a reamer. The bar needed to be at least 15 inches long and it just felt too flexible to get reliable diameters with it. I might practice using it on something less critical at some point. Reamers at this size are $$$.


The hole for the cam shaft was done in a similar manner. I made some slotted extension plates to raise the casting up. In some ways this is a trickier operation than the crank because the drill goes quite deep into the side of the casting so it is always wanting to veer off with the asymmetric loading. 
The internal side walls of this casting need an extensive amount of machining out to allow for the swing of the con rods around the crank and in retrospect it would have been better to do this first as it would have eased the pressure on the drill. Oh well. 




I should mention that the drilled holes were started with a center drill at each web, then drilled out and the next web center drilled progressively. Only the last drill and reamer really went all the way through non stop.
The results seem OK, that is the hole for the crank came out where it was supposed to!



The bronze bushings were turned and a trial fitting of the crank shaft made. The shaft sits in the bearings and can be rotated freely without that telltale tight, loose, tight , loose feel of misalignments. I need to make some new shims for the bearing caps, l lost the originals, their probably in the shop vac with 10 thousand other shim looking bits of metal.

The first couple of attempts at making the bronze bushes were not successful. I did the usual slitting of a bronze bar then silver soldered them together. Drilled and reamed but the solder joint broke both times. 

I had better luck with two flat bars of bronze half the dia thickness, held together in the four jaw.
 Whilst drilling and reaming  I also held the stick outs together with a C clamp (at slow rpm). So.. good news… no slit saw, heating the bronze or messing about with solder.
But… the technique is more expensive, not twice but getting there.

RS.


----------



## johnmcc69

I admire your persistence (& talent).

 It looks like you're making some progress!

 Keep up the good work!

 John


----------



## Ringsnapper

A bit more work on the crankcase and spot facing for the front cam bearing. The casting is a healthy 0.25 in thick here.





Aside from the ends there are three internal bronze bearings for the shaft, essentially rings that sit in the crank webs. The drawing shows they are to be held in place by 8BA screws tapped through the side wall of the crankcase. Not a big fan of this.


Having studied a couple of completed examples of this engine I have not seen any screws in the crankcase wall and I’m wondering what was done to secure them. Maybe they were superglued or the screws were brought through the webs rather than the sidewall?
Rear cam bearing trial fit.


----------



## Zeb

Ringsnapper said:


> Having studied a couple of completed examples of this engine I have not seen any screws in the crankcase wall and I’m wondering what was done to secure them. Maybe they were superglued or the screws were brought through the webs rather than the sidewall?


Superglue will flow at engine operating temp. Dutching the edges to lock the bushing is kind of meh. You could counterbore the bearing wall and set it. Is this end going to be submerged or splashed in oil?
I might:

preheat the case to a safe 250F or higher than the expected operating temp of the crankcase (ask wife's permission lol)
machine bushing OD Ø.0015+ oversize. I'm just eyeballing the bore sizes. Make extras and lightly chamfer.
Set bushings in bowl with liquid nitrogen and install using a simple home made tool on the lathe that fits the ID when frozen. Dry ice may not be enough but an easier alternative. I've used both for different projects.
Set the crankcase vertically and have a plate on the backside to keep the bushing from falling through (or flange it). If you go too slow the heat from the crank might freeze it halfway. 
The inner bore will shrink from compressive forces, you can line ream again or make test samples to calculate shrinkage.


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## Peter Twissell

There are high temperature locking compounds, e.g. Loctite 278, which are suitable for this application.
I've used similar adhesives in engines with no issues so far.


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## Ringsnapper

Thanks for your thoughts on this. In fact the drawings call for securing the cam lobes in position on the cam shaft using loctite.
The cam shaft isn’t submerged in oil but is constantly splashed by oil  from the crank throwing it about the casing.
 I’ll try shrink fitting the bearings first. I’ll look into liquid nitrogen though the containers seem expensive, or maybe just using freezer spray and some kind of locating tool. If that doesn’t work then plan B is the loctite.


The crankcase cam follower positions milled to height and holes drilled and bored for the lifter sleeves. Also the holes drilled and tapped for the cylinder head bolts using UNF 4-48 in place of 6BA.


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## Ringsnapper

Well to be fair to Les Chenery although I didn’t spot any cam bearing fasteners in the side wall of the crankcase in any model engines, I did find a real example of a Gypsy mk1 that appears to have some type of visible fastening at the right places on the crankcase adjacent the cam.


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## Zeb

Ringsnapper said:


> Well to be fair to Les Chenery although I didn’t spot any cam bearing fasteners in the side wall of the crankcase in any model engines, I did find a real example of a Gypsy mk1 that appears to have some type of visible fastening at the right places on the crankcase adjacent the cam.
> 
> View attachment 142792


Did the original have oil galleys (galleries) ported to the cam bearings? I could see ports being drilled then plugged.


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## D and D

I like to lock them with a grub screw.


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## Ringsnapper

Very nice. Yes that is what is indicated on the drawing using 8BA screws. I hadn’t seen the screws on the full size engine because most references to the Gipsy Moth show the later 120hp mk2 version which utilized a different arrangement.
I’m tempted to get a copy of a Gypsy 1 engine maintenance manual but I’d likely spend too much time perusing it at the expense of getting this engine built !


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## byawor

I have been working on my Gypsy on and off for awhile. Would it be ok to post some experience and pictures here or should I start a new thread?
Bob


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## Ringsnapper

Sure, I don‘t see any issue with you adding your experiences to this thread.
 I would suggest that if you have an extensive build story it might be best to start afresh as this thread has already rambled along over a number of topics for some time all be they Gipsy related.
Your choice though.


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## byawor

Trial fit of rocker arms. I had a lot of trouble finishing the supports, the castings are almost impossible to hold so it is difficult to get them right. I ruined a bunch  so I made  some replacement castings. If anyone is interested will post some pictures of the process.  Time well wasted!!
Bob


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## Peter Twissell

Yes please Bob.
Photos of the process are always interesting.
Glad to see I'm not the only one who works on the bench of chaos!


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## Richard Hed

byawor said:


> Trial fit of rocker arms. I had a lot of trouble finishing the supports, the castings are almost impossible to hold so it is difficult to get them right. I ruined a bunch  so I made  some replacement castings. If anyone is interested will post some pictures of the process.  Time well wasted!!
> Bob


This is why people read books--to gain experience without haveing to do the same processes that have been tried time and again thru the ages.  Your experiences, particularly the one that finished the product, can be helpful to others doing something smilar.  I am particularly interested n how you held the thing in the end.


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## byawor

This is how I did it. Drill and tap the three holes with center hole at x0y0. Rotate the block 90 degrees y stays at zero, set x0 at the base move y to y.495 and x to .687 these are the dimensions in the drawing. Picture shows where the hole would be and it just does not look right. I think it is ok in y but should be further up in x. I think the problem is that the "base" is too thick by about  50 thou. However there is no dimension given in the drawing. I hade the push rods adjustable so The hole maybe doesnt have to be exact  but its kind of hit and miss. The casting is made using the original as pattern.
Bob


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## Peter Twissell

Thanks for the explanation, Bob.
I assume you machined the base flat before drilling and tapping the holes?


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## Ringsnapper

Yes can’t wait to get started on the heads.
Just an update on the crankcase casting. I’m hoping to fit the oil pump to the crankcase so I‘m working on the various gearing for the cam, timing, and oil pump. Most of the spur gears and the helical gears I found as stock items in the HPC Gear catalog. I looked around in the US , Boston Gear etc. but didn’t get much joy. I only needed to cut one gear in the end for the crank shaft as the bore on the HPC gear is 5/16 and the crank shaft is 1/4 in.


I expect they would have made a custom gear if I’d asked. (The cost of shipping from UK to US is really expensive).

Also fitted the oil pump  gears after drilling the inlet and outlet ports. 
One point to note, and kind of obvious but the drawing calls for a 1/2 in dia recess to be drilled for the helical gear pinion shown below ( the upper most bore with a steel insert in it ). It’s really 3/8 in dia. , 1/2 in would break through the casting side wall.


Rgds
RS.


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## byawor

Had a look at the HPC website gear pricing seems really good. I have all the gears I need but paid a lot more than what it would cost from them.
Bob


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## byawor

Couple attempts at rocker arm supports. First thought I would try lost wax. Made silicone mold and cast the wax. Worked ok but  I had trouble making the plaster mold, tried couple times but could never get it to fill properly. The silicone mold will stand low melt alloy and makes a pretty nice piece but heavier and not as strong as aluminum. Second attempt is a steel mold as shown> tried it with wax and it seems ok will melt aluminum later this week.  If anyone wants the waxes to try casting I will send them to you.
Bob


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## Ringsnapper

I’ve never tried casting with lost wax, the burnout procedure always seemed long and complicated with temperature profiles etc. to get the wax out and dry the plaster sufficiently. I guess the original Chenery castings were lost wax.

I finally got around to fitting the lower half of the crank case. This is the casting bought from Keystone. I’d been putting it off because it needed a good bit of hand filing to remove metal from the front and rear beneath the flanges and get them wide enough to drill for the attachment bolts. The front is particularly awkward with many compound angles to contend with. The foundry left a lot of metal presumably to help with pattern removal in the sand.



Spot drilling for the 7BA screws but will use 3-48 UNC.


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## peterl95124

great work on a great engine !

my favorite sources for small gears are stock-drive-products in the US and rpcgears in the UK,
I'm in the US but have used rpcgears for some 15/48 helical that SDP doesn't stock.


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## byawor

Couple of pictures of a "real" Gypsy head


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