My build of Stew's Overcrank engine

[Lesmo]

Well I finished most of the 3d drawings and now have a better understanding of what makes this overcrank engine tick, so I made a start on the main bit, the engine block assembly.

I was uncertain whether to post this build so soon after Stew's own excellent build, but thought that it may appeal to anyone like myself who is short on experience and unsure whether to tackle something like this, having only one engine under his belt, or have been put off by having to silver solder such big lumps of brass together. Here goes.

During the drawing phase I decided to depart from Stews design and make the block from aluminium but keep the brass cylinders. My reasoning being, with brass costing an arm and a leg, one machining screwup could be expensive, more so,if I screwed up twice. So I bought a chunk of 75x75mm ally enough for several attempts if necessary, for the same money as one lump of brass.

I was a little uncertain given the nature of ally whether it would bond with the brass cylinders so I did an experiment using araldite two part epoxy, I bonded a half circle of scrap ally to a 16mm brass dowel and left it overnight to cure. The next day I put the ally in the vice and was surprised at how little force was required to break the joint. I suppose there must be ally etching adhesives out there as Lotus use epoxy for bonding ally on their sports cars, but I could not find anything on the net, so it was back to the drawing board to re-design the block so that I would not have to rely on bonding alone but use a clamping action to hold the cylinders in place.

I made the block a little wider than the half circle shown on the plans, then it was out to the shop to make a start. First I carved a chunk of 75x75 ally and faced the ends square

Marked up the orientation of the clamp bolts and cylinders

then split it across the cylinder centerline with my band-saw and faced both halves

which were were then drilled and tapped for 4mm cap heads.

After assembly it was all faced up square and the centers marked for the cyl positions.

They were center drilled

Then drilled through with an 8mm drill followed by 12mm 16mm and 20mm endmills

and finally bored out to 20mm using a gauge plug to ensure the correct final size

Without moving the piece, the 5mm counter bore was carried out, using a dial indicator for cutter adjustment and a hole gauge and micrometer as a double check.

The piece was then moved to the other cylinder position and the same operation repeated until I had this.

So far so good. Next up were the brass cylinders which were a fairly straightforward turning job, creeping up very gently on size and making good use of the dial indicators on both X & Y feeds and using the split ally block as a further check.

With the material leftover from the cylinders I made 2 backplates for the cylinders and put them to one side for a little decorative work later.

Next I turned the cylinder heads.

The heads call for a ME 5/16 32 tpi 6mm deep threaded blind hole and I only have metric taps & dies, and 60 deg thread cutters, also my 8mm shank internal cutter will only thread a 10/11mm hole, so the hunt was on for a cutter that could cut a thread in a 7mm ish hole.

After searching the net I eventually found what I was looking for here http://madmodder.net/index.php?topic=3523.0 so taking a length of 8mm silversteel/drill rod I was able to produce a cutter that would cut inside a 7mm hole and hardened it.

First set up the lathe to cut 32 tpi, fitted one of the cyl heads into a collett chuck and bored the hole part way through the head to accommodate the gland nut, the hole is as mentioned, 7mm diameter and 6mm deep. the the cyl head being 10mm deep. I wanted a full depth thread but had to find a way of stopping the tool crashing at the end of travel and wrecking the part and the tool. You will gather that I am still a newbie.

I wound in the tool until it bottomed out and set the dial indicator that sits in my adjustable table stop to a reading of plus 0.35 mm. This is just over the distance the table travels whilst cutting, from the time the Di needle moves off zero, to my releasing the clasp nut. It is my reaction time plus a bit. As you can guess I had practised this with a few dry runs to see what my worst time was, and when I had a consistent time, I went for it. Success, the male thread fitted spot on with no sign of play.

I had cut my first blind full depth thread without wrecking the piece or the tool. There are probably far better and less nerve racking ways to do this I am sure, but it was a case of needs must, and I must admit, I do like threading on the lathe so it was quite satisfying.

I certainly look forward to any helpful comments as to how it should be done.

Back at the engine block I dry assembled the cylinders and nipped up the clamp bolts then lightly faced the block and cyl's both back and front.

I put the block aside to do the decorative work on the cyl back plates. I had the previous evening been playing with the 3d cad to see what the cutting patterns would be like for a given radius of cutter, depth of cut and the offset from the disc center. They were all based on an 8 point star. I had previously seen a small star on one of Stew's other builds, I think it was the popcorn engine, but wanted something larger.

I set up the rotab with 3 jaw chuck fitted and a collett chuck in the three jaw chuck chuck, you get the idea. The cutter set at 35mm rad & 2mm off centre and the cut 1mm deep.

Worked like a dream and came out exactly as the cad model predicted.

Playtime over, that's me up to date with the story so far.

 

[vcutajar]

Hi Lesmo

I do not think I know the engine you are building but will follow your progress and see it take shape as you go along.

I got lost a bit with the internal thread you made. Is it a metric 7mm thread?

Vince

 

[Lesmo]

Hi Vince

Thanks for looking in. Here is a link to Stew’s build showing pics of the original engine which inspired his build. You can read the whole thing rather than waiting for my installments

http://www.homemodelenginemachinist.com/index.php?topic=12367.0

The thread is a bit of a hybrid, it’s essentially a 5/16 ME thread but with a 60 degree included angle, instead of 55 deg, it is a nice fine thread ideal I guess for the purpose intended, and as I said I only have 60* cutters.

Cheers Les

 

[SBWHART]

Hi Les

That's a great start and I must say that's a very cleaver way to fabricate the cylinder.

Now why didn't i think of that ;D ;D

When you get the cylinder done that's the worst part over.

Hers my engine running

[ame]http://youtu.be/FBEsz7imfh8[/ame]

so newcomers can see what its about.

Stew

 

[mzetati]

Hi Les,

definitely another build worth keeping an eye on.
Thank You for posting the link to Stew's thread, too.
Marcello

 

[doubletop]

I've seen enough so far to lock myself in. I'm here for the ride

Pete

 

[vcutajar]

Thanks Les and Stew for showing the engine.

Definetely will be following your journey Les and admiring your work.

Vince

 

[steamer]

Nice job Les!

Dave

 

[rebush]

Les: What a wonderful looking engine. Will be here for the duration. I'm sure I'll learn volumes.

Stew: Thanks for the post of the engine running. As always a beautiful piece of work. You really set the bar high.

Roger

 

[danstir]

A really nice build thread. Thanks for sharing!

 

[bearcar1]

I'll be tagging along on this journey into the depths. ;D Some very careful and thought out work you are showing us Les, thank you. It's fun to see a tried and true design such as Stew's come to life using different methods. Same destination only a different road so to speak.


BC1
Jim

 

[Don1966]

Hi Les I will be tagging along also. I like the way you go about your work very interesting and I can learn something here.

Thanks Don

 

[Lesmo]

Thank you for your very kind comments guys, it always warms the heart to know that you are out there taking the time out to write a few words of encouragement, or advice if the need arises.

I will do my best to have this build measure up to the extremely high standard set by Stew, who’s video I have just watched again Thanks for posting that Stew, it is all the inspiration I need for the task that lies ahead, and is just great for visitors who can see what I am trying to achieve.

I have in fact just emailed the video link to a friend who dropped in last night to see how I was getting on, and present his finally completed project. A pristine 1936 Ford V8 3.6 litre complete with white wall tyres. I thought it was Al Capone turning up on my driveway.

Cheers Les

 

[dsquire]

Lesmo

You know that you should have had the camera at the ready. We want to see some pictures of your friends pristine 1936 Ford V8 3.6 litre complete with white wall tyres. :bow:

Cheers

Don

 

[Lesmo]

Hi Don

It will be done, as it happens my pal Steve tells me the car was manufactured in Canada, it is a RHD version. I will post some pictures shortly, Oh and I was adrift on the year, it is in fact a 1934 model

Cheers Les

 

[Lesmo]

Here we are guys as requested, some pictures of Steve's baby.

That's it for now, work on the project has been interrupted because I am fitting a DRO to the mill before I go any further.

Les

For some odd reason the pictures have appeared severely cropped, although they are my usual size ???.

 

[clivel]

It will be done, as it happens my pal Steve tells me the car was manufactured in Canada, it is a RHD version. I will post some pictures shortly, Oh and I was adrift on the year, it is in fact a 1934 model

Oh I didn't realise that Canada drove on the left until so recently, not recent enough for me though
My first week after moving to Canada I looked right (as I had done my whole life) to cross the road and stepped directly in front of a bus. I was fortunate; I don't know why, maybe the angle of the blow, but apart from a few cracked ribs, a lump on the head and a bruise that covered every inch of my body the biggest damage was to my pride. This happened during peak hour traffic on one of Vancouver's busiest roads. So not only did I have to contend with the attentions of a bus full of concerned passengers, I also had to suffer the embarrassment of being responsible for a major traffic jam.

I am really enjoying following your build Les, and the pictures of the car are a nice bonus

 

[dsquire]

Les

Thanks for the photo's Les. That sure is a beautiful car and looks to have been very carefully restored. The fact that it was made in Canada is just icing on the cake. In the last photo of the engine you can see "Made In Canada" cast into the cylinder head.

Cheers

Don

 

[Lesmo]

That was a narrow escape Clive, there aren’t too many people walk away after being hit by a bus, much less feel embarrassed about it. I had a close shave myself years ago. I spent three years in Germany when I was in the RAF and driving on thr right became the norm.
When I was demobbed and drove my old (Rommel style) Mercedes home, I arrived in the UK at two in the morning with almost no traffic about. I came out of a junction and strayed over to the right then at the first roundabout I went around it the wrong way and just after the exit from it, I encountered a nutter (so I thought) in a big lorry on my side of the road. Fortunately I escaped but embarrassed doesn’t even begin to describe how I felt. :-[ :-[

Glad you liked the pictures Don, she is a beaut and no mistake. She’s four years older than me but has certainly weathered the time a lot better. Maybe I should get a restoration job. :big:

 

[Lesmo]

After fitting the Dro to the mill, I modified the lathe by fitting a limit/cutout switch into the electrical circuit, specifically for use when internal threading blind holes. It saves the fear of crashing the tool into the work if my reaction time is not quick enough. I wont go into detail but here are a couple of pictures which explain how it works.

The thread in the second cyl head was done using this mod, and it was a breeze compared to the first one.

***

Now back to the job in hand.

Armed with my new Dro the next task was to drill/mill the valve steam ports into the block. I started by removing the brass cylinders from the block so that it would fit into the vice when I came to mill 15* taper on the top of the block as I do not possess a tilt table. First I drilled the side ports and counter-bored the outer ones to accept the brass sealing plugs which would be made later.

Next I set the block to a 15* angle in the vice using a digital angle finder, and milled it flat (No pic). I then drilled the top steam passage to join up with those in the the sides, and using a 3mm endmill, started to mill out the required slots. I then realised that I was milling in the wrong plane as you can see in the picture. Next I compounded the cockup by milling it in the correct plane, but not engaging the brain before doing . Consequently I over-shot the slot limit by 1.5mm. I had not taken the cutter radius into account, in my calculations.

Fortunately I had only taken a 2mm deep bite, so having cooled down, I could see that a rescue was possible by reverting to my original plan of covering the area of the steamchest with a 2mm thick brass plate that would provide a better wearing surface. I just needed to mill out a 2mm recess in the top of the block, then bond and screw it in. Not having any brass plate in stock I decided to continue to mill out the slots and drill the steam chest stud holes, so that I didn't waste the day.

Finally I milled the 2mm recess to accept the brass plate which I had on order, and that is when I discovered yet another major cockup. All the slots were offset by 1.25mm, which is evident in the next picture.

That makes three cock ups one after another. I can only put it down to the fact that I was trying to get to grips with the new DRO and not paying enough attention to what I was doing. I would certainly advise anyone fitteing a Dro, to get a little practice in first, on something unimportant, not something into which a lot of time and effort has already been invested.

No excuses, but if anyone knows of a chimpanzee willing to do a brain swap, in exchange for a years supply lovely of ripe bananas, get in touch please

While ordering the brass I also ordered a tilt table which would enable me to keep the workpeice in the plane I was used to seeing it on the drawing, and not confuse my poor old brain as it had in the first of the *^&>" moments when the x and y planes were reversed in the vice.

This is the block set up on the T/T on the workbench prior to transfer to the mill, which was being used for milling the brass plate to the correct width, leaving just a couple of mm extra on the length

and the T/T setup on the mill, aligned, and tilted to 15 degrees ready for fitting the brass plate. It will be fitted using two 3mm countersunk brass screws, coated on both surfaces with a thin layer of Araldite steel epoxy before tightening down and leaving overnight to cure

This time around, I made sure that all the hole coordinates including the two holding down ones, were correctly programmed into the dro and each one manually checked in turn using a length of 2.5mm rod in the chuck. I also double checked the slot co-ord limits again.

Both retaining holes were drilled and tapped 3mm. Araldite was then applied to both surfaces and two temporary screws inserted to hold it whilst it set.

Here you can see the setup I used which included my small laptop so that I could transfer co-ords from the drawing to the dro reducing the error potential. (I hope) and If you look closely you can see the brass plate bonded in, and with temporary screws in place ready for machining.

The brass plate was milled down to just above the ally surface, all the 3mm stud holes drilled and tapped, and the 6 slots milled in the correct place, I then turned the two countersunk 3mm screws on the lathe to replace the temporary ones presently holding the plate.

The screws were cut flush to the surface using a fine hacksaw, and the whole surface was then fly-cut to a smooth finish