# New 2.5 cc Model Diesel design and build.



## edholly (Oct 11, 2016)

I haven't been too active here for a while, as I have been busy with finishing off a 1964 Lotus Seven which is so much fun to drive, along with building a 160% Tomboy powered by a modified Owen Mate for the recent Oily Hands weekend at the Cowra Model Aero Club in honour of David who I miss very much.

With 14 model diesels now made and running over the last  few years - 2 of which totally my design, I think the time has come to lay down another engine along the lines of the Owen Mate, the BollAero 18 the Midge and many others. I want to keep it very simple, but with a good turn of power for the weight of the engine and have penciled a few ideas over the last little while. 

What I would like to do is to go through the planning process as an insight how this might be done by other budding designers and for someone to follow these ideas and rough drawings up with a CAD plan. So if there is anyone out there that would like to put these ideas into this format please let me know. I want the end result to be freely available to those that would like to build it, maybe HMEM might have a suggestion in this regard. 

The initial idea is for front induction, bulkhead mount, around square bore/stroke, not too tall, conservative timing and ball bearing suspended shaft. To this end I have settled on a 14.6mm bore x 14.6mm stroke giving a capacity of 2.44 cc Initial drawings show a 13mm piston length and timing of 107 deg inlet and 122 deg exhaust. The initial drawing is working out timing etc and is to scale 2:1 it is attached along with a couple of photos of the engines built so far. Once the bore / stroke / piston length / port placement thereby read timing is decided then the bones of the engine can be designed around it. That will be the next phase.

Re the images, the first one is this latest design in progress drawing, next is a .5cc engine with longish stroke but good power only finished a few weeks ago after about a year of hap-hazard work, the next is a 1.6cc side/piston port design which gives reasonable power, Next is of a batch of others and the final one is of all the engines with names to them.

This proces may take a little while, but I think it should be a bit of fun and hopefully inspires some others to have a go at designing an engine, which is very rewarding.

Ed


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## Herbiev (Oct 12, 2016)

Nice collection you got there Ed. looking forward to the 2.5cc build.


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## edholly (Oct 16, 2016)

Here is the next installment - about 2 hours work laying out the cylinder. This aspect was done using the parameters developed from the initial sketch above. Note that the exhaust port has been narrowed from 3mm to 2mm. The various lengths have been decided now and incorporated into the drawing. 

I ran the Type 14 again yesterday and from its .5cc it gave 10100 on a 6x4 Tornado prop and was getting better with each run, that equates to an Allbon .5cc when on the same size prop. Now the Type 14 has only 2 inlet transfer ports and 2 exhaust ports, and is very easy to start. So I have decided that this engine will have the same, 2 only transfer ports of reasonable size, I am sure this will enhance starting as you get better gas speed at flicking speed than you do with bigger transfer area. Like wise it will have 2 exhaust ports 90 degrees away, again as per the Type 14.

Next step is to design the crankcase and crankshaft and rod etc ...

Note correction --- the 2 transfer ports should read Drill 2 x 8mm holes at a PCD of 10.5mm ... this will leave 1.05mm meat to the outside of the cylinder at the widest point.  These are the little things that make designing so much of a mind exercise except when you have to start a drawing again from scratch because of a big stuff-up the eraser can't get rid of !!

_Have fixed the drawing now with a new scan._


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## edholly (Oct 16, 2016)

OK next phase of the design is to decide on a few crankcase details.

1. gudgeon pin height - free to choose, if a bit lower down the piston than half way means the conrod can be a bit beafier and still have freedom of movement, so lets say 7.5mm from the top which is 5.5mm from the bottom.

2. The thickness of the bigend. For a 2.5cc engine somewhere around 4.5mm should be sufficient, smaller is slightly less friction but higher point loading, too big and it means the tunnel is expanded. I would think 4.5mm is a good compromise.

3. Bigend conrod surround thickness. I would say a 2mm thick rod with square shoulders should be sufficient. I like square shoulders as you get more strength in the rod, maybe not as aesthetically nice as a round rod, but strength is more important to me in a home built engine.

4. Now we can decide on the tunnel diameter. So we have stroke 14.6 plus outer half of crankpin over hang = 4.5mm, conrod surround 2mm either side = 4mm plus some blending of the crankdisc to the bigend say 2mm = 4mm but this is negated by the conrod surround so can be discounted, and some clearance say .9mm all round = 1.8mm. So the sum is 14.6+4.5+4+1.8 less = 24.9mm - so lets say a tunnel diameter of 25mm.

5. We need some meat in the crankcase and around 1.5mm wall thickness at narrow point would be about right which makes the crankcase 28mm wide for the tunnel. Tunnel length is pretty open but it is easier to make the crankcase a square so 28 x 28 and the minimum length can be determined from the drawing allowing for the piston to descend fully without hitting the crankdisc, and this works out to 40mm from the land at the bottom of the exhaust ring of the cylinder to the bottom of the tunnel plus the 1.5mm wall.

6 The next step is to incorporate these parameters into the drawing and see how it all fits.


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## edholly (Oct 17, 2016)

Have now put the crankcase parameters into the drawing and initial thoughts on crankshaft design within the crankcase.

Note the inlet transfer ports have been slimmed down to 6mm from 8mm. I think 8mm would slow the gas speed too much. Have also shown the exhaust ring with either a slitting saw cutting the apeture, or you could use a slotting drill to make them if you don't have a slitting saw. I've shown a 20mm diameter saw, but any smaller diameter one will do, just go in so that the length of the slit is about the same. 

In this drawing you will see the crankdisc with the crankpins 5mm long drawn at tdc and bdc. The disc is 5mm thick relieved a bit to create a land for the 10 x 19 x 5 deep ball bearing, a pretty common and not expensive size that will run to over 30,000rpm on the NTN catalogue.

Now as I am writing this I realise that there is a problem - the housing for the bearing is going to block a major portion of the forward inlet transfer port, so in the design of the housing it will have to be relieved here to create a free passage for the gases.

The crankdisc will be 21.1 diameter (14.6+4.5+2)and the shaft size at the ball bearing will be 10mm.

Having said all this - with this cylinder design you are not limited where you rotate the cylinder, to have the ports 90/180/270/360 degrees to the engine or maybe better still 45/135/225/315, that way no blanking of one of the inlet transfer ports. Although for aesthetics I would like them 90/180/270/360 - but you can always experiment by turning them once it is running of course. although once assembled and run in not a good idea o disturb the hard won piston/cylinder finish.

If you are still with me on this you can see there is a bit in just coming up with a simple design, sure wish I knew how to do CAD, as my penciling skills are pretty slow !


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## Blogwitch (Oct 17, 2016)

No need to worry about CAD, rough line drawings are just fine.

But if I can make a suggestion, either use a softer pencil or a much darker felt tip as the sketches are a little faint and difficult to make out.

Keep up the good work.

John


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## edholly (Oct 19, 2016)

We are now in the final phase of the design. A myriad of notes are on the drawing, I am using a 5.5mm hole at the bottom of the venturi with a 5.5mm hole in the shaft with a timing of 50 degrees BTDC on the upstroke of rotation. This gives around 135 degrees of inlet opening which then gives a timing of 118 degrees BTDC to 17 degress ATDC, which is quite a reasonable timing for a higher performance sport engine.

The drawing incorporates most of the other parameters so now just the conrod and the ancilliaries - backplate, cooling muff, drive washer and compression screw to go. I won't worry about a needle valve, the PAW ones are terrific, can tell you it is a very tedious job making them and I cheat by using bought ones!

With regards the muff, I will draw one, but it is very much a personal preference as to how they look and I encourage anyone tackling this engine to have a go at designing their own, like wise the backplate. After all this whole excersize is about encouraging others to do a bit of design work, and hopefully the steps here will help a bit.

As to a name - well I've though long and hard and was wondering if 

the  "Holly Buddy"  might suit.

I have the utmost respect for David Owen and I love his Owen Mate, and this name is a bit of a take on what David called his - anyone care to comment ?

Ed


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## edholly (Oct 23, 2016)

Here is the piston and the conrod drawings. The notes on them are pretty explanatory. Note the piston/rod assembly is probably a bit heavier than normal, so there will be some metal removed from the crankdisc to help counter-balance this. I think making these components just a bit heavier and therfor more robust is very worthwhile for a non-commercially produced engine.

A lot of PAW engines don't remove crankdisc material yet do not suffer from excessive vibration, so anything we do to help reduce that tendency should be good.

Note the conrod crankpin to gudgeon pin centre to centre length is 26.05mm


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## edholly (Oct 24, 2016)

Terrific news, 

Aussie Steve has been working with me converting the rudimentary drawings onto CAD. He is now up to date with all I have done so far and I can tell you it is very impressive. Steve has his own way of doing things, which is a bit different than past CAD drawings I have used and I have to say Steve's way is quite a bit easier to understand with regards the various radius's.

It will soon be getting to the time to start carving up some metal.  :thumbup:


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## edholly (Oct 25, 2016)

Here is the start of the making of the crankcase. Had some beautiful heat treated 42mm diameter aluminium, it machines like a hot knife through butter.

Machined off a piece just over the 41.25mm length then milled it 28mm square.

So we have made a start - now to do the lawns before dinner, or I will be in big trouble!

Note Steve's CAD drawing adjacent to the block.


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## edholly (Oct 26, 2016)

Here's the maybe finished crankcase - maybe because not sure now if I will radius the outside edges above the nose and rear cover - was going to but don't mind the look of it with the square edges.

total time so far 5.5 hours, with 4.5 hours spent this morning carving up this piece.

Have to say again how easy it is to achieve this with digital read outs on the mill don't know how they got on before they were invented, although I do know with good marking out you can get to within a few thou - but with DRO's that is a few microns !

Made this directly of Steve's CAD drawing. Next thing is the cylinder.

1st photo is removing bulk of the tunnel
2nd is boring the tunnel to 25mm
3rd is using the mill to hold the tap square to start the M3 tap
4th is the finished piece.


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## edholly (Oct 28, 2016)

Well here's another hours and a half's work, yet to be lapped. 

But I have to admit I spent about another 90 minutes playing with some 10/20 then 10/40 material that I was never going to be happy with the finish. Eventually found my 12L14 in a big enough size - then stuffed up the first attempt because I didn't do my homework reading Steve's CAD drawing - even though Steve did it from my ones !

In a way that was a good thing, because Steve has now changed the drawing and the wrong garden path I went down no longer exists. The things we do for future builders 

OK so here are some photos of the cylinder in its raw state straight off the mill and lathe. Internal bore looks pretty good, and I have about 2 thou left to work with to get the nominal 14.6 mm bore size pretty much exact. This of course doesn't matter too much unless you want to use it in competition ! Yet to cut the exhaust slits.

Shown here is a drill making the 6mm bypass holes - I took this to .5 mm short of the correct length and used a slot drill to finish to depth to get the square edged finish as can be seen in the photo.

The bearing is the right size, came with seals which will be flicked off to make it open.

Will leave the lapping for now, and get on with the front housing.
.


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## edholly (Oct 28, 2016)

Here is the cylinder with the slots cut in. Used a 40 mm diameter 2 mm thick slitting saw and went in 7 mm. I have a slotting arbor but it is too bulky for this type of work so made up a simple saw holder as shown and it works a treat.

But you could achieve the same result almost using a slotting drill. If doing this I would machine on the lathe a 2mm wide relief, 2 mm deep to reduce the flex on the slot drill, and I would make multiple plunges and then join them up by slotting it in multiple passes.  

For info held the cylinder in one of my 5C collets - something David Owen told me to buy and they are terrific for holding work like this.

Hate how the photos always seem to enlarge the blemishes !
.


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## Dalee (Oct 29, 2016)

Hi,

Thanks for sharing all your hard work of designing. For us newbies to engine building, learning how to think about engines and how the parts all must work together can difficult to grasp.

I will be following this your work!

Dale


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## edholly (Oct 31, 2016)

Thanks Dale.

Making the crankshaft next. Reason - it is easier to ream the bore of the crankcase nose to size, rather than machine the shaft.

There are various ways of doing the crankpin onto the shaft, I used to prefer a pressed in pin, but more recently I have changed to machining it on using the 4 jaw.

Here you will see the dimple at 1/2 stroke length done with the DRO's on the mill so that I can accurately align the end of the crankshaft in the chuck. You could of course mark it out instead.

You can also see I have roughed out some of the bulk the other end of the shaft so that it better fits in the 4 jaw, I prefer to do the interrupted machining holding the large diameter of the piece rather than stressing the smaller machined end, probably doesn't do any harm, but better this way, that is why I have left a bit of "meat" on the end of it near the crankpin. 

Next job will be to machine the front end of the shaft to size, and to that end there is a small centering hole at the front end. I will machine it about 5mm along the length of the large diameter, then move it out of the 3 jaw and machine the next 5mm and so forth - that way I am not stressing the small thickness of the crankshaft web with cuts on a big overhang off a small chuck engagement.

Once this is done turn it around and bore the intake hole down the centre, otherwise it would have to be held on the finished crankshaft which is not a good thing.

Then turn it round again and mount it on the 4.8mm crankdisc and take smallish cuts down to nose shaft size.

Last thing to do is the drill the 5mm venturi intake hole - but this has to wait till the engine is further advanced - after assembly of the nose to the case, place the shaft at the correct rotation - ie 50 degrees BTDC then rotate it till this point is under the venturi hole - then with a sharp pin like instrument, scribe around the hole to mark the shaft. Then drill the hole in this position. Make sure you get the right side of the shaft, otherwise it will only run backwards!
.


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## Blogwitch (Nov 1, 2016)

Very nicely done and shown.

It was because of making a very tiny one just like yours that eventually led to a contract to make very small parts for model steam locos and me basically getting a new workshop paid for by a company I used to work for.






Cut from the solid silver steel using a 6" 4 jaw independent chuck on an Atlas 10F lathe using a HSS toolbit.

Big things from little acorns grow.

John


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## edholly (Nov 1, 2016)

John, Beautiful work, machining long cuts off centre is a pretty difficult exercise and just holding that sort of thing becomes a nightmare. Thanks for sharing it.

Here is the almost finished crankshaft, just needs the venturi hole drilled when the nose is made and some weight removed for better balancing. A few notes ..    

The taper is 8 degrees, the length of the threaded front portion is a bit longer than specified, but can be trimmed down later. The thread calls for 6M but I didn't have a 6M die, so used a 1/4UNF. The ball bearing is a light press fit onto the land next to the crankdisc. I didn't read my own instructions above and forgot to drill the inlet hole. I didn't want to hold it with the finished bearing portion so held it further out where the thread is, Thankfully it had no run out so drilled it and just chamfered the opening slightly, taking care not to knock the crankpin with too big a centre drill that I used. 

I normally start the thread using the thread cutting facility on the lathe, but this time I used a very good die and made sure it was 100% square with the work by chasing it down the threading action with a flat disc (pic 3)held in the drilling chuck. I have had a thread wander off and cut more one side than the other, especially on a long thread such as this, and the die I use is quite large and unforgiving of any angle at the start.

Note that the piece is held with the crankpin in the middle of the chuck jaws so as to not bruise the area around it which will be quite stressed when running and if bruised could be prone to cracking.

Finally note the high tech way of determining where to start the taper ! 
.


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## Blogwitch (Nov 1, 2016)

Ed,

Maybe you can use this method some time in the future.

When you have cut your taper, most probably by using the topslide (compound), you usually have to move the topslide back to where it started so that you can complete the job in hand before you have had chance to cut the taper in the prop driver, so sometimes it can be a little difficult getting the taper to be exactly the right angle as the taper on your crank.

I have used this method on a few engines in the distant past and it has worked perfectly every time. Not my idea, but one I pinched off a plan by ETW.






What you do is to machine your crank without the taper, leaving a nice smooth corner face for the separate taper to fit to.

The advantage of this method that the taper cone and the taper in the prop driver can be cut at any time but at the same time, ensuring you don't have to move your topslide between cutting each one.
All I used to do is cut the taper cone first, in the same orientation as you cut yours, then when machining the prop driver, just try the taper for length fit in the taper being cut, once it is within a couple of thou of being all the way into the prop driver (to allow for a slight compression of the cone), only then do the saw cut.

Just maybe it helps in the future

John


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## edholly (Nov 2, 2016)

Thanks John, can see how the split collar frees up using the angle of the compound slide, I will try it in the next engine. I usually try to leave the angle set after putting it on the shaft, till I make the prop driver, that way I get a perfect match, but I have also managed to dial it in after moving it with reasonable success.

Here is the nose almost completed - just need to mill the overhangs straight off the bottom and the 2 sides, will leave the curve at the top, but this could be removed too of course.

A few photos of it being made.

1. machining the ball bearing land.
2. reaming the crankshaft tunnel to size. 
3. finished inside with just a small lead on the end of the tunnel
4. mated to the case with the shaft installed for the first time.
5. setting the "flat" of the cutter to the angle I want for the nose. (high tech)
6. machining that angle.
7. the result with a bit of polish.
8. attached after boring the 30mm pcd holes and counter boring to hide the heads.

Next instalment will be the muff, need this to hold the cylinder in place before making the piston, contra and rod.

Once again want to remind everybody - this is not just an excersize in making a new engine - it is mainly to try to inspire anyone who wants to design an engine how I have gone about it, with the help of Steve who is following up each piece with a CAD drawing which will be available for anyone who wants to build this. Well assuming it runs ok .... Ed


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## edholly (Nov 3, 2016)

Job for the morning was to make the prop driver and washer. Now for a surf at Wanda beach.

There are a couple of things about making the prop driver which might be helpful in other situations. The photos tell the story, but firstly I want to mention BOKUM tooling. I was very fortunate that a mate gave me some of these and until then I had great difficult boring very small holes to size and that includes tapers. But with these gadgets, it is now a simple task. They are not cheap, but I would recommend if you intend to do any engine building, then you definitely should source at least 3 - 1 very small - 1 medium and 1 for internal threading. They are made of magnificent tooling steel and I have never had to sharpen one, admittedly mostly used in alloy, but I have used them in steel too, especially for internal threading where I normally go for about 32tpi. Their website is at http://www.bokumtoolco.com/PRODgallery1.htm

I will divide this post up a bit as too much for just one. Note the compound slide was still at the same setting from when I made the taper on the crankshaft, so a perfect fit is assured.

Photos:-

1. raw plug for prop driver with a BOKUM boring tool about to go to work.
2. trial fitting the crankshaft, taking the taper out bit by bit to be within about .4mm to the crankcase.
3. taking a bit more out of the taper.
4. happy with the fit, about .4mm or 15thou
5. turned the slug around to machine the back out of it, note the flat in the chuck to ensure the work is totally square.
6. machining the taper to match the crankcase.
7. to faciltitate moving the cutter out of the way, I use a simple digital read out on the longitudinal bed - this has been a huge boon to machining an absolute must to put the toolpost exactly where you want it for work like this and especially internal work where you cannot see what is going on.


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## edholly (Nov 3, 2016)

This is the process I use to cut the "drive" into the prop driver. Very simple, and works a treat.

Using the cross cutter move it about 3 thou into the work. I have divided my chuck into 20 divisions with a simple texta mark. Lining up the mark with anything thin and available I move the chuck to the next division and move the toolpost into and out of the prop driver. Having done that at about 3 thou I then make another cut at 5 thou, and this is the result.
you will see there is a prop washer - but I won't be doing a drawing for that - something to be designed and made yourself - or just use a 1/4 - 6mm propriety one.


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## edholly (Nov 5, 2016)

Here is the muff, once again when Steve finishes the CAD plans, you will see how this one was made. Muff's are so distinctive and a small change in design can totally alter the look of the engine, so if you decide to build this engine, once again think of redesigning it to your own preferences, maybe a ball, maybe a taper to it, alter the thickness and spacing of the fins ... etc, the parameters you work to are, 28 PCD for the bolt holes and enough meat above the top of the cylinder to bolt them through and also enough meat for the tommy bar to not over-stress the threads. 

Remember to keep the internal fit snug, it needs to be to transfer heat efficiently from the cylinder wall, you can use a bit of heat sink paste if it isn't snug though, and it needs to be just a tad short of touching the lower ring of the cylinder, you want the hold-down bolts to hold the top of the muff to the cylinder otherwise A) the cylinder will float in the slackness and B) the expansion of the alloy will be greater than the cylinder which will also cause slackness and stress the bolts at the same time.

Speaking of the tommy bar, David Owen taught me to always drill a hole in the centre of it where it contacts the contra, that helps centre it and avoids stressing the threads by it wanting to wander side to side. The tommy bar shown here is just a 4mm cap-head, it will be a proper one in time.

Getting closer now - piston, rod, backplate venturi and tommy bar to go...


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## edholly (Nov 7, 2016)

Venturi done - found it needed to be a little beefier than the design, so Steve will fix that in the plans. Also found Steve's interpretation of my hole in the crankshaft under the venturi was awry - so Steve will fix that too. Finding out now that mud map drawings are all fine and dandy for the one who drew them - but not so easy for the one trying to make sense of it all !

Have to spare a thought for all those like Steve trying to interpret other's thoughts and notations.

Here are a couple of photos. including one little bloke who continues to think he can fly - 4 times now I have put him back in the tree ! His parents go berserk when I pick him up - if only I could talk to the animals and tell them I am trying to help him out. There are a couple of cats that frequent the backyard so I hope he gets his golden wings soon. By the way he is an Australian Butcher Bird - they have a beautiful song but can get a bit aggressive, have had my ear ripped open a couple of times by them - not these ones - they are pretty gentle despite thinking I am doing him no favours !

P1 - milling the flats for the needle valve - note the %C collets to hold it
P2 - boring the venturi hole
P3 - In place ready to scribe the inlet hole in the crankshaft with a sharp needle
P4- setting the crankpin at 50 degrees BTDC
P5 - venturo in place, actually stuffed up slightly and a bit of a sloppy fit. Araldite or locktite gets a better grip this way !
P6 - the one who thinks he can fly


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## edholly (Nov 7, 2016)

Couple of jobs done today. 

First the marking out of the crankshaft venturi hole at 50° BTDC. As can be seen a sharp needle will just mark the steel enough to notate where the opening is. Then with a centre drill just nick the metal till you are sure it is centred then put a lead in with it. Then use the 5.5mm drill to go through. I use a wide flat very fine diamond file to get rid of the burr on the outside and a drill on the inside. It is important not to remove any parent metal as the better the seal around the venturi hole in the crankshaft to the crankcase, the better the suction of fuel/air mixture into the engine.


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## edholly (Nov 7, 2016)

Next was making the conrod. I don't think anyone really enjoys this task, I certainly don't relish the thought of it. Anyways it seems to have come out ok.

I think it was Ron Chernich who came up with this idea initially and this is a bit of a modification on that. I mount a drill the exact size of the pin - vertical in the mill right on the edge (and I also use a drill the same size the other end of the jaws so as not to cock the jaws unnecessarily). I then use an end milling cutter in the chuck.

Now this is where you have to be super cautious as your fingers are pretty (very) close to the spinning cutter and you mill the ends of the conrod as per the photos. Once done you then mount the rod and mill the rise in between the rounded ends. Makes for a nice rod, but you certainly have to bear in mind how close your fingers are to the cutter, and the fact that the cutter wants to pull the work around. I only cut about 6 to 7 thou at a time to manage this best.

Of course you can always use a linisher or a file, I have done so plently of times, rarely anyone except you gets to see the rod, so as long as it is strong it doesn't matter too much if it isn't particularly pretty!

Note the 1mm hole drilled in the bigend for better oil supply and the slight chamfer on the crankshaft side of the rod for the slight radius on the crankpin to crankdisc.

Oh the Butcher Bird got his wings today - whew ...


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## edholly (Nov 8, 2016)

The next step is to lap the cylinder with not just a fine finish, but also a taper from the exhaust port to the top of about 0.1 thou. Yes, this is pretty fine tolerances, but I have achieved that using the lap that has to be made.

The first thing to do is to clean up the bore with a reamer and get it as near as straight or open a bit at the bottom end by a thous or so.

Then make the lap, this is about a 10 minute to make affair, simply machine a piece of ally rod to the inside diameter of the bore less about 2 thou. for about 20 mm, drill and tap with an ordinary tap anything you have on hand (I used a 1/4 UNF) with the most tapered one. Taps are of course taper, medium and end, we want a taper one. Then hacksaw a slit all the way through for about 24 mm. The overall length of the lap needs to be about 60 mm or more so it can be held in the lathe chuck. - see photos.

Cover the bed of the lathe with some protective material, you don't want lapping paste getting on the beds etc. I use a diamond paste to do the lapping with. 

Now put a grub screw, or even an ordinary cap head bolt in the lap and force it open with the grub screw and load the end with a bit of paste and I use 1 drop of oil too. I load the cylinder with the conrod end towards the end away from the chuck, as the lap will give a natural taper opening out in the direction which is what we want for the internal bore. You will need to keep reloading the paste and a tiny bit of oil. This process can take a hour or more so be patient. 

Then with an in / out motion bring the bore gradually down to a fine finish. You will need to keep checking the taper, which means scrupulously cleaning everything. I have successfully used the lap to measure the bore, but have recently bought a bore gauge which reads in 1/10th thou increments.

The last photo shows the finished article now with that taper.

The reason for the taper is because the top of the bore is hotter than the bottom and expands a tiny bit more, and this allows for that. In the perfect world of model diesel engines, the piston should be a squeaky tight fit over top dead centre, but enter the bottom of the cylinder around the exhaust with little friction. If you achieve this you will have a beautiful running engine.

Next is the piston. Using the lap you can get an idea of the size required, and we are talking to 1 or 2 /10ths thou. A lot of people make a lap also for the piston. but I have found that this gives less a result than the process I will explain next post.

Just to recap - I can't emphasize enough how important a slight taper is, and it is worth the time and effort to get this.


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## edholly (Nov 9, 2016)

Here is how to work out the internal diameter with the bore gauge. Yes 1 (ie 1 to 2)  division on the dial is 1 thou how accurate is that !    

I take a number of readings as the gauge is more for comparison than measuring. I got 570.5 - 570.8 - 570.2 - 570.5 and the calipers said 570.5 .... so wil make the piston 571 to start with and take it from there with the process I use.

You can still get almost the same accuaracy using the lap by winding the grub screw in and out ... ever so slightly ..


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## edholly (Nov 9, 2016)

After making quite a few of these engines, you can still work out ways to improve what you do. 

Contra pistons have to be a tight fit in the bore, and I know from experience that a tight fit (contra) to a nice fit (piston) is usually .2 thou - so it will be interesting to see when we make it.. So methinks why not make the contra first and use that as a sort of template to make the piston ? This is the first time ever I have made a contra first, usually I treat them as a bit of an afterthought - but really it might be a much better way !

So that is what I have done here. Starting off at 573 thou made the contra with its 4mm deptth and 2mm relief. Now it would only just enter the bore at the bottom. Taking it down by about .1 thou at a time I got it to enter to the exhaust ring at about 572.4 another .1 off and I could force it to about 1/2 way up the bore. another .1 off and I could force it to the top of the bore, still very tight had to tap it with a piece of dowel, but that is what is required of a contra if it is not to leak. This also proved the taper in the bore is what was aimed for.

This then gives me the size to aim for for the piston, I'll make it 572.1 to start then take it down if necessary from there. The last photo is of the finished contra needing the pip removed.


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## Mechanicboy (Nov 10, 2016)

To create tapered cylinder: Piston create tapered piston when the piston is lapped into the cylinder at final stage. 
To test fit is correct: Dry piston/cylinder ---> tight to enter into cylinder. Oiled piston/ cylinder ---> The piston is loose fit in BDC cylinder and tight in TDC.


Lets take a look at a typical lapping job - that of producing a fine finished bore and piston for an IC engine. In fact, piston and bore are both lapped in separate operations (NOT both together). All of these operations will be carried out in the lathe (and I need hardly mention the importance of keeping lapping compounds off the machine, particularly the chuck and slideways). For the bore an expanding lap is ideal, and this should be some 3-4 times the total length of the bore. The first grade of abrasive would be mixed with light machine oil (10W or lighter) and liberally coated on the inside of the workpiece. Similarly, the slurry would be added to the outside (and inside assuming it is of the ventilated type) of the lap. The lathe would be started at about 300rpm (for a nominal 1" bore) and the lap passed rapidly through the bore, keeping it moving back and forth without it coming out the bore. How to hold the lap? well, perhaps the best way is with a 'floating' tailstock holder, and failing this holding with the hand is a method as good as any. Be careful when holding the lap by hand as it's possible it may jam, hold it lightly and expect the unexpected. Remember also that unless the lap is maintained dead parallel with the bore (an almost impossible task) it will tend to bell-mouth the bore a little - hence the reason for making the work a little longer than finished size and trimming to length later. When the inside of the bore has achieved an all-over grey appearance, with the fine scratches appearing even and criss-crossing both ways, and with no evidence of any deeper scratches (as might be left by the reamer) it's time to move onto the next finer grade. The work will have to be removed from the chuck to clean it properly, and this should be done with clean paraffin oil followed by hot soapy water. The same procedure applies to the lap and all traces of the abrasive must be removed. The process continues until you reach the 'flour' grade of abrasive by which time the finish on the workpiece should be very fine indeed. A final polished finish, should this be deemed necessary, can be achieved using metal polish (diluted Autosol, or some liquid chrome cleaner). The lap should be a separate 'finishing' lap so there is no chance of contamination with the coarser grades of abrasive which might be embedded in the main lap. The piston is treated in a similar way except of course the lap is female. Work will continue with the coarse abrasive until (using the un-trimmed bore as a gauge) the piston will not *quite* enter the bore. At this stage finer grade abrasives are used and work continues until the piston will just enter the bore tightly. At this stage, it is usual to finish mating the two parts by using metal polish and briefly using the piston to lap the bore directly. Great care needs be taken but this method ensures that the fit is good for the entire length of the bore.


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## petertha (Nov 10, 2016)

edholly, my interest always perks up when it comes to cylinder lapping. Did you happen to record your pre-lap & after-lap bore ID dimensions? (ie. how much material was removed during the lapping process).


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## edholly (Nov 10, 2016)

Mechanicboy, thanks for the insight as to how best to make and use a lap. I have found this simpler way for both cylinder and piston that works for me and is not as labour intensive. Obviously the way you describe will give wonderful results, but my way too gets the engine running pretty satisfactorily.

Petertha, After running the ream down the bore a couple of times, it cleaned up very nicely. The actual lap only removed about .3 thou to get it where I was happy. I have found the more you dwell on getting a perfect lap the more risk there is of making it bell shaped inside, I think the lap follows the less material around the exhaust. The most critical thing from what I have found is the slight and evenly made taper from bottom to top. I found with this engine holding the cylinder with the bottom away from the chuck works in your favour as the shape of the lap is biggest part away from the chuck, so you aren't fighting the natural shape of the lap.


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## edholly (Nov 10, 2016)

Here's a photo fo everything washed in the ultra-sonic cleaner with kero and then Nulon Carby cleaner. The ball bearing finally had its protection seals removed and the grease inside washed away. The venturi was Devcon'd into the nose and then whole engine oiled up and assembled.

The backplate was made and attached, the tommy bar was made using the caphead bolt with some ears put through it, and a mount made.

I have put in another couple of photos to show how I accurately get a centre with the slightly bent centre finder. Note the arrow on the top of the belt driven spindle - I turn that arrow to the direction the centre finder is being used - that way all errors are cancelled out and you get a centre within microns of where it is. If I was to find an edge I average the readings with the arrow to and the arrow away from the edge. Simple but it works everytime.

Forget to mention, when I made the piston, I stuffed up a bit and it ended up .4 thou smaller than the contra - I wanted it .2 Nevermind can either make another or cherry bomb this one. It has reasonable compression but not as good as if it was just .2 thou larger. We'll see what happens ...


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## edholly (Nov 10, 2016)

Here is the finished engine, the comp is in fact a little soft as said in the previous post, but that didn't stop it from starting reasonably quickly and running superbly. I ran it for about 3 minutes on a very rich setting and right at the end just tweaked the comp bar a bit and the revs rose beautifully on the 9 x 4 prop. It augers well for when it is run in and can be leaned out and up-comped. Just took this short video of it running, this truly was its first ever run .... Ed

[ame]https://www.youtube.com/watch?v=FkDS0WEEWTQ[/ame]
.

I must thank Steve who has worked so hard to follow my rough sketches for the componentry.  Steve has almost finished the CAD plans, just the rear cover/engine mount to go and hopefully we can publish them in the next week or so. It is a pretty simple negine to build, and Steve's CAD plans do things a bit different to other plans I have worked from, I find them a lot easier to follow, and a couple of pitfalls I fell into have been changed around so no-one else will make them ...

.


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## petertha (Nov 11, 2016)

Looks good, congrats. That brings back memories when I was a kid. Guys screwing the compression tommy bar in & out, open exhaust, engine rpm ebbing & flowing, slimy castor oil soaked hand, usually with an open knuckle wound form recent a prop shaving


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## Roboguy (Nov 11, 2016)

Great looking engine and very informative build thread, thanks so much for sharing! Amazing how quickly you've built this. I'm hoping to get my Boll Aero finished in the next week or so.

Cheers 
James Fitzsimons


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## Herbiev (Nov 11, 2016)

Great build and great write up.


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## Cogsy (Nov 11, 2016)

Great engine and built so fast as well!


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## shodan (Nov 11, 2016)

Thank you! Super build, can't wait to try build one myself, as soon as plans are available. Cheers!


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## edholly (Nov 13, 2016)

I was disappointed with the soft compression, entirely my fault, just machined the piston a tad too close to final finish to be able to get a good surface on it at the size I was aiming for and ended up .2 thou smaller than intended. When I measured it after disassembly and after the running it had, it was in fact .5 thou smaller than intended.

So it was either make a new piston or "cherry bomb" this one. Decided on the latter, nothing ventured-nothing gained. First heating no growth. Second heating a delicious 1 thou growth. Made a mandrell and pushed the piston onto it and then linished it as before. Took it down to the 572.2 size finished I was aiming for in the first place. It looked a treat.

Reassembled the engine and as I had hoped, the engine would not turn over but  the piston did enter the bore to a bit more than 1/2 stroke. Plenty of light oil and then with a prop on worked it back and forth for about a couple of minutes, each time it went just that bit further. Not too hard as the conrod and gudgeon and crankpin are all being a bit stressed whilst this process goes on.

Eventually the engine went full circle, very tight, but that is exactly what is required. I never cease to be amazed how an engine will start and run with so much tightness .

So on to the test bed, fuel and flicking. A few pops then a few rotations, then a few more then away. Maybe not quite so quickly as this sounds but it didn't take too long.

First run just let it burble away at low comp for about 3 minutes, with a bit of a tweak right at the end. Let cool down 100% then another 3 minutes and a tweak at the end gave 8600 on the 9 x 4 wood Turnigy prop I have always used for comparisons. Totally cooled and 3rd run starting to tweak it often even a little leaner, although that indicated where I had it was about right, this time just got to 9,000 again about 3-4 minutes. 4th and last run tweaked it for max and got 9,060 initially, backed off next tweak 9100, backed off next tweak saw 9250. I then backed off the comp and let it run at about 5500 and then it ran out of fuel. So after about 12 -15 minutes it is showing some wonderful signs.

A) Good power.
B) Getting better with each run.
C) Easy to start, just suck a little fuel through the spraybar and flick.
4) Compression - fantastic - as good as it gets cold or hot.
5) Vibration certainly within the low to average range.
6) Never made any black in the exhaust, so materials must be happy.

So there we have it - an engine that would probably be the equal of a good sport 2.5cc from the 50s or 60s that can be built by the Home Machinist and hoping to inspire budding designers to have a go at their own design.

Time now to put the CAD plans on here.

A bit about me. I think my first flick of a diesel engine was about age 12, it was a Taipan red head possibly a Mk5 if I remember correctly, that was the only diesel I had as a kid. I must profess that I am a new-comer to playing around with building model diesel engines, and have only scratched the surface of what knowledge those involved in the Motor Boys camp have. But I enjoy using my mill and lathe immensely and that is where all this started a few years ago when I built my first engine the BollAero 18. The Holly Buddy is the 15th one built and I guess it won't be the last. 

Again I would like to mention Steve Jenkinson who has so kindly worked these CAD plans from my rudimentary drawings into easy to follow and a joy to use plans of the engine. 

And as you will see I have dedicated this design and build to the memory of a terrific fellow aeromodeler, David Owen.


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## edholly (Nov 13, 2016)

Here are the CAD plans for the Holly Buddy.

Please read the "Forward words for Buddy Holly" before building the engine there is a wealth of information here.

If you do decide to build it, would very much appreciate a PM to me.

Ed 

View attachment Forward words for Holly Buddy.pdf


View attachment 1- Engine.pdf


View attachment 2- Crankcase.pdf


View attachment 3- Cylinder.pdf


View attachment 4- Crankshaft.pdf


View attachment 5- Conrod piston.pdf


View attachment 6- Nose.pdf


View attachment 7- Venturi&Propdriver.pdf


View attachment 8- Cylinder Muff.pdf


View attachment 9- Back plate.pdf


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## Blogwitch (Nov 14, 2016)

Here you are Ed, all bundled up and ready to download as one item.

John 

View attachment Holly Buddy Plans.pdf


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## edholly (Nov 29, 2016)

Thanks John for consolidating the pages.

Gave the "Holly Buddy" another run this afternoon and the getting better with each run scenerio seems to be true, this was the best I've seen so far, 9660. 

Maybe 10000 with this prop is not outside the realms of possiblity, my Owen Mate Mk2 gave 9500 on this prop so I am very happy with its performance so far. Bear in mind though that the Owen Mate is just 2cc - the Holly Buddy is 2.5cc.

It is handling very nicely, easy to start both hot or cold, in fact hot is even easier. It must be getting close to being run-in about 6 to 8 x 3 minute runs now.


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## steve-de24 (Nov 29, 2016)

Hi Ed, nice engine and good build log. Many thanks to both you and Steve Jenkinson for most generously making the drawings available. 
Regards, Steve


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## modelmotor (Jan 15, 2017)

Hallo Ed

Thank you for sending me so soon the drawings from your engine.The Holly Buddy 2,5 model diesel engine you made is looking great and runs great as well.I saw all your selfmade model engines you and i must say you are a real well skilled engine builder with much knowledge about constructing small model engines.
I like your engines very much.

 many greetings from modelmotor-The Netherlands-Europe.


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## bollaero (Mar 16, 2017)

You are making much better drawings than I do at the initial stages.
How will you ensure that the liner screws in so the gudgeon pin is well clear of the ports, or maybe it doesn t matter in your design.
I like either to leave a very small shoulder between the crankpin and web, or to make the big end slightly thicker than thhe rest of the rod, so there is no chance of the rod rubbing on the web, a few thou only is ok.


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## smartrobert (Mar 16, 2017)

I love it. Thanks for sharing with us.


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## Stieglitz (Mar 16, 2017)

Hi Edholly, Great to see someone designing model aero engines,I have been inspired by(but not yet committed to start) by Chris Boll's designs.
I will follow you build ,please more photos and CAD drawings.
Cheers.


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## itowbig (Mar 18, 2017)

wow great build. you guys do good work one day ill be able to do such good stuff. love the builds , seeing what everybody makes and the awesomeness of the skills. it inspires me more an more.


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## edholly (May 14, 2017)

I would like to acknowledge the award by HMEM of build of the month for the Holly Buddy. There are a great many other engines that I think are just as deserving as this one, so I feel very honoured to have it awarded to a fairly simple design and relatively easy build.

I last ran this engine a little while ago and did get 10200 rpm consistently with equal parts castor oil / kerosene / ether and some DII.  Trying some less quantity castor oil and equal parts ether and kerosene and no DII fuel just now, it is down on this power slightly, but the fact it did achieve over 10,000 rpm was very pleasing.

I would like to thank Steve Jenkinson again for doing the plans in CAD in a way that I think is very easy to understand and not so easy to make mistake from. I would also like to thank David Owen to whom this engine is dedicated for his help and encouragement when building an engine was still a daunting task.


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## modelmotor (May 16, 2017)

Hallo Ed
Congratulations for receiving the award by HMEM for the build of the month for the Holly Buddy 2,5 cc model diesel engine.The concept you designed is a great looking engine that probably can be build by many modellers all over the world.The fact that you choose of a model diesel engine will bring old times alive.

                                                                     many greetings from Gerard- modelmotor-The Netherlands-Europe.


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## Stieglitz (May 16, 2017)

Hi, great project thanks for posting ,will we see the finished motor running?
Cheers
Allen


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## fishy-steve (Jun 12, 2017)

Hi Ed,
I can't  find a 3.6mm PAW spraybar. Would it be possible  to measure the relevant  dimensions  so I could make my own.
This would be  my second build so I do not have much experience  in these things.
Thanks.
Steve.


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## edholly (Jun 13, 2017)

Steve,

Here is the PAW NVA.

Length of threaded section 12.5mm ; overall length this component 27mm ; diam where holes are 3.55mm ; inlet holes (2) are 3.9mm from fixed end and staggered maybe .5mm ie one is 3.6 and the other 4.1 from fixed end and the 2 holes are not diametrically opposed but are 90 degrees apart. I think you can work out the other bits needed from the photo ... 

Ed


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## fishy-steve (Jun 14, 2017)

Thanks Ed.  
Steve.


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## fishy-steve (Jul 27, 2017)

Hi Again Ed.
Thanks for making the plans available  and thanks for the NVA details. Here is my effort.

https://youtu.be/aNLCgsiNe-U


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## modelmotor (Jul 27, 2017)

Hallo Steve,
Your Holly Buddy 2,5 cc model diesel engine looks great to me.You made the engine in the right way and style so you might be very proud of it to reach such a high level .
My congratulations for you and your very nice finished engine project.
                                                                                                      many greetings from modelmotor-Gerard-The Netherlands-Europe.


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## edholly (Jul 27, 2017)

Hi Steve,

You have made a wonderful job of building the engine - it looks superb in the photos and in the way it runs in the video you posted. Congratulations, you should be very proud of your efforts.

Kind regards ... Ed


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## fishy-steve (Jul 29, 2017)

Hello Gerard and Ed,
Thanks for your kind words.
I ran the engine again today. I'm  still running it in . Having very little experience  of these engines every start is a learning for me.
I really would like to design my own engine but I just don't  have the required knowledge.

https://youtu.be/2iCIVznUzvA


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## fishy-steve (Aug 6, 2017)

Hello all.
Having recently finished the engine I found myself with a desire to design my own engine based loosely on Eds  "Holly Buddy" and David Owens "Owen Mate". That is a Front Rotary Valve (FRV) engine that would be relatively easy to design and build for a beginner like myself.
Immediately I came across a rather big stumbling block. That being, I haven't  got a clue what I'm  doing. &#55357;&#56841;
So I decided I would reverse engineer Ed's engine. Starting at the beginning I thought it might be prudent  to understand  the port period angles, that Ed mentions in the introduction, that come with the drawings ie 107° transfer period, 122° exhaust  period and 140° intake period.
I spent two evenings trying to come up with  figures that matched Ed's. I failed miserably. I then got in touch with Ed who confirmed that his figures could also be wrong.
 I then  searched Google  for "2 stroke port timing calculator" and found myself on Ron Chernich's fantastic site. http://modelenginenews.org/index.html To find the calculator, in the yellow bar on the left, click resources, design centre, Front Rotary Valve (FRV)
I entered all the required dimensions and the calculator spat out the timing diagram.
I then sent a message to Ed with the timing diagram. He has asked me to include it here for completeness .
As  I stated  earlier I'm  very much a beginner. If anybody spots an error can they please correct it here.
Thanks.
Steve ( on behalf of Ed)


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## Keith140 (Aug 9, 2017)

Hi to all,is it possible to convert the B/Holly to a glow plug version as I would like to use it in a aeroplane, diesels vibrate a bit to much!! I understand a compression ratio of about 8to1 is required any advice or suggestions would be very much appreciated many thanks Keith


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## mu38&Bg# (Aug 11, 2017)

fishy-steve said:


> I spent two evenings trying to come up with  figures that matched Ed's. I failed miserably. I then got in touch with Ed who confirmed that his figures could also be wrong.



https://www.rcgroups.com/forums/showpost.php?p=36347313&postcount=12246


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## fishy-steve (Aug 11, 2017)

And the penny drops !
Thank you diesel pilot.  A quick glance at the drawing you've linked to made me realise  my school boy error.
I can now do the math using the cosine rule. :thumbup:


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## edholly (Dec 29, 2017)

I have always been of the opinion that most home machined engines like the Holly Buddy do look a bit squared edged which detracts a bit from their aesthetics and in fact I designed the HB this way and encouraged those making one to customize their engines by softening this aspect of them.

Just prior to the HB came a small 0.5cc conventional engine and in fact a picture of it can be found on page 1 - it is the 2nd photo in this thread. That engine inspired the internals of the HB and it gives as good a power as any of the late 50's early 60s commercial .5cc motors. It has slightly softer lines but still has that square edged look. One way around that is to do a casting, but then the cost associated with that defeats the objective in my opinion. I have spoken to Steve Jenkinson who did the HB plans  about doing CAD plans for the .5cc one, but somehow we never got past the talking about it stage ..

I have been playing around with an idea of inserting a tube in a tube and have done a mock up, albeit on a larger scale than this engine will have. But of course not not sure if it will work - only one way to find out I guess. A photo of this mock up is here alongside the HB and the .5cc little fella. This item is pressed together with Loctite and pinned with 4 x 1mm music wire as can be seen in the photo below. I am of the opinion that this will work in a tiny motor like this where the firing pressure forces are relatively small, an hydraulic lock on starting probably the worse it will experience.

For the next project I would like to design and make a 020 size diesel. To make it an easy handler - a longish stroke and a piston port induction is envisioned, a Mills .75 uses this type of porting for instance.

I want it to be a practical engine that can be used to power a small free flighter, or lightweight RC model. I love really small diesels.

I have started down the road of putting pencil to paper. The engine from necessity with the cylinder in a cylinder design will need quite some thread machining, which shouldn't be too difficult as I think it can be done in the primary machining process before removing the work from the lathe in the first instance.

Some rough measurements are 9/32" bore (.2813") and a 0.32 stroke. With tiny diesels a longer stroke and piston length I think will help with gas seal on the piston / cylinder walls. This gives a capacity of 0.0199 CI.

The Cox 020 is called a Pee Wee so what should we call this ? ... How about the Wee Dee ... for little diesel ?

I will start a new thread on this if there is any interest shown ... 

Ed


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## bollaero (Dec 29, 2017)

Good luck with it, any small engine demands precision fits and low friction to run at all, this is why DC abandoned the Bambi as it was too expensive to make consistently well, I guess Cox had very sophisticated machine tools so could overcome the difficulty of achieving tight tolerances.

I am working up to larger sizes, now have a 7.5cc diesel which flies a 7foot span plane well.


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## edholly (Dec 29, 2017)

Thanks Bollaero - I will start another thread as I have started on the initial design phase. Yes fits will be very important and never considered friction - an easy build will minimize friction errors so will try to achieve that. Like your suggestion of Teeny D - but might stick with Wee Dee ... cheers


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## Niels Abildgaard (Dec 30, 2017)

bollaero said:


> I am working up to larger sizes, now have a 7.5cc diesel which flies a 7foot span plane well.



Pictures or videos?
Please?


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## edholly (Jan 6, 2019)

The current AeroModeller January 2019 magazine has a 4 page feature on the Holly Buddy written by Maris Dislers.


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## stackerjack (Jan 8, 2019)

edholly said:


> Have now put the crankcase parameters into the drawing and initial thoughts on crankshaft design within the crankcase.
> 
> Note the inlet transfer ports have been slimmed down to 6mm from 8mm. I think 8mm would slow the gas speed too much. Have also shown the exhaust ring with either a slitting saw cutting the apeture, or you could use a slotting drill to make them if you don't have a slitting saw. I've shown a 20mm diameter saw, but any smaller diameter one will do, just go in so that the length of the slit is about the same.
> 
> ...



I've been using Autocad for about 5 years now and I find I can do a drawing in about the same time as it takes to draw one with a pencil. The advantages are: Mistakes don't show and I can copy it as many times as I want and print it exact size. I learned how to use it by borrowing 3 books from our local Library and going through them during one Winter. There are also tutorials on You-Tube.
In the UK, the Model Engineering Workshop Magazine is currently running an article on ALIBRE, another drawing tool. You can also download a FREE TRIAL of the sofwtare through the magazine.
Jack


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## edholly (Jul 30, 2019)

I have been thinking for a long time about building a flat twin engine - but always got hung up on the need to use either spit big-ends or use a built up crankshaft. Well I have finally bit the bullet and decided to make a twin using a "sort of" built up crankshaft. It might not work, but I think it will and only one way to find out. The twin is based on the Holly Buddy and if you are interested the thread for it is at https://www.homemodelenginemachinist.com/threads/a-flat-twin-version-of-the-holly-buddy.31463/ 

 regards to all ... Ed


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## josodl1953 (Jul 31, 2019)

Split big ends are a feasible  option, see my flat twin at https://www.homemodelenginemachinist.com/threads/longest-project-ever.27251/  Only you may need very thin bolts to hold them together. In my flat twin I used m2 Allen bolts.

Jos


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## edholly (Apr 27, 2020)

Been a while since l posted here - the Holly Buddy continues to run well and I have decided to try to make it a more normal looking engine with a rounded crankcase. 

To that end ... here is the pattern to have some Holly Buddy crankcases cast by a local non-ferrous foundry. They have done work for me before for a 2.5cc TBR version of the Owen Mate and also a ED Baby. They can do rough sand cast or smooth - David Owen seen the castings and asked if he could take a cut on the ED Baby casting - and was very impressed with it, a tiny cut on his Hardinge lathe and the swarf came off like fairy floss. The castings were each heat treated before delivery and were a joy to machine. David had had work done by these people about 30 years prior and was disappointed back then but could see that this wasn't the case here - about 5 years ago now.

I have loaded a few photos - and ask for opinions - if you were having them cast would you go for rough or smooth ?

My intention is to get one cast - prove the work by building an engine and if ok then get maybe 10 cast up for anyone that wants to build the engine - and l will simply ask the cost of the casting and postage. I have made the pattern to use the Holly Buddy plans for the componentry to complete it so no redesign of the engine. 

The first photo is the pattern - second the pattern with the machining extensions shown - third the Holly Buddy in front row and the 2.5 TBR Owen Mate back row - last is the ED Baby with smooth casting finish and the Owen Mate with the rough sand cast finish. I will do the proving casting smooth - as l want to see if there are any major blemishes that need to be removed ...

I would like to put an embossed motif on the outside but can't find anywhere on the web that says how to do this. Something along the lines of a circle with a H inside. No hurry for that - the proving casting doesn't need it.

Any opinions as to the rough v smooth would be appreciated as would anyone that wants a casting please let me know. I intend to start a new thread detailing the cast crankshaft engine build ...


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## edholly (Apr 27, 2020)

For those interested in the pattern - it is made from Aluminium and the various bits were glued together and a bit of filler used to fillet various bits - then a coat of silver paint. Took about 10 hours to make maybe a bit more - but it will cut down the build time considerably, especialy for an engine with beam mounts.


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## Ghosty (Apr 27, 2020)

I think the smooth looks better


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## NickP (Apr 27, 2020)

I’d go for smooth too - just think it looks a little more ‘finished’ - I like rough castings for steam engines though


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## SteveT (Apr 27, 2020)

Smooth also, and let me know when available.
I completed my first ever machining project a HB2.5 and it runs beautifully. Now in the middle of making a batch of 3 for friends.
If you ever intend to modify the basic engine, provisions for a silencer and throttle would be fantastic.
Many many thanks for designing the engine and making the plans available.
Steve T


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## Cholchester (Apr 27, 2020)

I would like to put my name down for one. Any idea of the price yet? Smooth finish is the best.


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## 777engman (Apr 27, 2020)

I'd be very keen to acquire a few castings to mate, go for the smooth finish, looks way better and a lot more professional.
Regards
Dean


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## edholly (Apr 28, 2020)

Dropped the pattern off to Camcast this morning - looks like $60 AU including heat treatment each .... which is not much more than they charged for the castings l had done about 5 years ago 

Can you guys that have indicated you want one or more please email me ... edholly at optusnet dot com dot au ... makes it easier for me that way ... 

It will probably take about 3 weeks before l get my one back to trial build with - then if that's ok then will get them done after that. Getting close to 20 castings requested so far ...


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## Chris Murphy (Apr 28, 2020)

Ed-as per my reply on 'another' forum-put me down for one of each-the Buddy and the ED Baby (and should you be tempted to do another run of David Owen 'Mate' BB case castings-one of them as well..!


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## 777engman (Apr 28, 2020)

Chris Murphy said:


> Ed-as per my reply on 'another' forum-put me down for one of each-the Buddy and the ED Baby (and should you be tempted to do another run of David Owen 'Mate' BB case castings-one of them as well..!


Yup, same for me for any other castings mate, emailed you already today.
Cheers mate thanks heaps
Dean


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## edholly (Apr 28, 2020)

Dean, didn't get an email from you yet ??


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## 777engman (Apr 28, 2020)

edholly said:


> Dean, didn't get an email from you yet ??


Check your spam folder


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## edholly (Apr 28, 2020)

Still nothing there ...


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## jcreasey (Apr 28, 2020)

Hi Ed,
I have often thought about making one of these little diesel engines.
My biggest concern is where to find the fuel for them.
I notice you are in Sydney, is there a supplier in Sydney that has suitable fuel?


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## edholly (Apr 28, 2020)

There is a source here in Sydney - best send me an email at address 3rd last post previous page this thread ...


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## edholly (Jul 26, 2020)

Hi guys,

An update on the casting.

The initial one took quite a while to have done as the heat treatment only gets done once every three weeks or so - then when l got it, it wasn't very smooth l think because some of the casting sand was still attached to the pattern, so when the casting was done it was quite rough.

I picked it up the day the guy that l deal with wasn't there and so took it back a little while later and he took it and had the foundry guys have another go. This time it is better but not perfect. I got the impression that the foundry guys see it as a nuisance something so small and fiddly compared to what they normally do, maybe l am wrong.

The guy l deal with said that if l make a pattern plate for them to use with 2 engines on each half of the plates then he can stay at the first agreed price which was $60 to you guys. I don't have the resources to do this and the cost of having it done is prohibitive - so will stick with the pattern I have. So to continue with the pattern as is then the price to me will be $80 and l would have to charge it out at $100 plus post to you.

So have a think about it, it is quite a cost increase. All the previous correspondence from you will be set aside for the time being, and when I am happy that the casting works then I will recall for expressions of interest then, so please be patient. I hope to start the build this week and knowing how these things go then it will probably take 2 - 3 weeks to get it done. It will be diesel engine no.20

Here are the photos of the casting as received.


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## edholly (Jul 28, 2020)

Guys,

Thanks for staying with me on this - will now start a new thread for the Holly Buddy Mk2 build to help any future builders with my experience making it. cheers ... Ed


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## Tim Wescott (Jul 28, 2020)

edholly said:


> The guy l deal with said that if l make a pattern plate for them to use with 2 engines on each half of the plates then he can stay at the first agreed price which was $60 to you guys. I don't have the resources to do this and the cost of having it done is prohibitive - so will stick with the pattern I have. So to continue with the pattern as is then the price to me will be $80 and l would have to charge it out at $100 plus post to you.



That's frustrating to hear you say, because my brother makes matched plates and makes it look easy.  Of course, he's been doing it for a long time, and "makes it look easy" is a heavily loaded term.

Given the flask sizes my brother is building for (about 2' by 1 1/2'), you could get at least a dozen castings at a go -- I'm not sure what size flask your foundry is working with, though.


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## modelmotor (May 6, 2021)

Hallo Ed,
Sorry Ed that i did n`t write to you about the finish of my Holly Buddy model engines.As already mentioned earlier in this article about the making of i told you about the new engine parts i made,a liner and a piston to solve my starting and good running problems.I succeed indeed in making the right quality of parts the engine does have the real strong compression which normaly has been  needed to get a good running engine.I am real proud on the results short runs are Ok ,but it is very difficult in the neighbourhood were i live to run the engine with higher RPM and for a long time.My country is very small so possibilities to run an engine is very difficult.I will have to find a solution maybe in a shed or something like that.The dieselfuel is possible to make now in a bigger quantity because i do have some more of the ingredients to do so.I will stay in contact with you as allways and soon as the possibilities are changing i will let you know about this.Unhappily i felwt down the stairs and the fall has giving me much problems  with much pain,but easily i will perform some more again i hope.

Many greetings from Gerard-Didam-Holland(The Netherlands-Europe).


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## edholly (May 6, 2021)

Hi Gerard, sure sorry to hear about your fall - we don't bounce as well as we did when we were younger .. Great news about the Buddy ... perseverance pays off, and the fit is not easy to achieve. Well done Gerard .. and thanks for letting those interested in this thread know ... cheers ...


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## josodl1953 (May 8, 2021)

Gerard,
Mount your engine on a small table and take in to an industrial area on Saturday. Most companies are closed then so you can make as much  noise as you want.  I test run my engines on a Workmate in a nearby industrial estate...no problem at all.

Groeten uit Rotterdam,
Jos


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