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Your Own Design / Re: Ringbom 1: Tim's Ringbom Stirling Engine Build
« Last post by tvoght on Today at 02:08:45 PM »
Those viewing the pages with a recent version of Chrome browser should now be able to see the photos. I had to setup the web server to also allow https access. We can proceed with the build.

The cooler (in 6061 aluminum) came next. A chunk of 2 inch square stock was cut slightly over-length and centered in the 4-jaw, then a hole was drilled and reamed clear through for the displacer rod bushing. That hole can be seen at the bottom of the larger displacer cavity that had been bored to depth here.
The hole was bored ever slightly deeper than required and then the end was faced to establish the design depth.

A recess was bored to accept a flange on the hot cap.

This shows that a form tool was made to cut a groove for a sealing o-ring at the bottom of this recess. Ultimately, a wider square-section o-ring was used here and the groove serves no function.

The cooler was clamped in the CNC mill for a fin-cutting operation. The clamps to the sides served to ensure no lateral movement.

A 3/32" saw was used with a CNC program to cut the fins. A slow operation compared to cutting these in the lathe, but good luck has been had with the method, and some frustrating bad luck trying to do it with a lathe.
Also -as you'll see- some of the fins do not extend entirely around the cooler, so a lathe operation would not have worked for those anyway.

In the lathe, the cooler was centered on the hole that had been previously reamed for the displacer rod bushing. A boss was then turned, No photo is shown of that operation.

Here in the mill vice you can see the boss that was turned, and that holes have been drilled and tapped to match up with those previously made on the mating face of the cylinder. The hole in the middle provides direct connection from the cylinder bore to the displacer bore in the cooler. Plenty of cleanup still needed.

A corner was rounded off to build character for this part. It was decided to use a coarse step in the round off to give this scalloped effect. An observer at a show asked in a surly tone why in the heck it was like that. To each his own.
You'll also see the adjacent corner was truncated for appearance.

This photo shows a new and now-favorite tool, this edge-finding device. It is mounted in a dedicated tool holder and then adjusted to eliminate runout. It is a very accurate tool. Here It's being used to find the middle of that bore using the Osborne maneuver. What's not shown is why: holes were drilled surrounding the hot cap flange recess. Those will be for a clamping ring which will hold the hot cap.

That's all the existing photos of cooler operations, but one more step taken was to mill each of the 4 flat sides with a face mill just to cleanup the extruded faces and any clamping marks.

Thanks Bear, and good to know that you are still hanging in there on your engine.  Glad you found my pictures helpful.  That strap is tricky to hold securely while still allowing access for the machining operation.

When I first tried using the rotary table, I found it difficult to see how to clamp the parts I was making, and what order to align which with what.  I found that tooling plate plus a few carefully made pins made setting up and clamping small parts on centre to acceptable accuracy much easier.  But I am sure there are others on the forum with additional and better methods to facilitate alignment.

Hi Ron,  thank you for the comment on my attempt to add my own stamp to the eccentric rod.  But I know what you mean about the part taking a long time.  Each operation takes seconds, but the setting up, and thinking before the cut takes all the time.  And so many operations.  But it is nice to reach this stage.

Not much progress today, first COVID shot this morning, no reaction so far, Mother’s Day dinner with our two sons and their family’s this evening.  Maybe tomorrow.

Well there you go - that's exactly what I was going to search for.
Your Own Design / Re: Buffalo steam engine model
« Last post by rarach22 on Today at 12:03:23 PM »

From Plans / Re: Elmer's Grasshopper
« Last post by joe d on Today at 11:46:53 AM »
That came out really nice.  I do like the flywheel as well :cheers:

Your Own Design / Re: 1/4 Scale Cosworth DFV Engine
« Last post by JonC on Today at 11:20:44 AM »
Hello Jon,

That looks to be a very practical solution to the staggered cylinders and belts.  :ThumbsUp: :ThumbsUp: :ThumbsUp:

I assume the crankshaft pulley has the two belts running side by side.

I am impressed with your idea of building a plastic mock-up to tease out all the tolerance and clearance issues before you commit to the castings. You cannot afford to find problems, once the die is cast, as they say.


Hi Mike,

Yes, both belts run off the crankshaft

From Plans / Re: Bruce Macbeth Engine, European Version
« Last post by Vixen on Today at 10:58:30 AM »

I always admire your skills and love the way this engine is coming together.  :ThumbsUp: :ThumbsUp: :ThumbsUp:

Two questions?

What screw threads are you using? I ask, because the nuts have nice proportions. Small metric nuts are all the wrong shape for models. They are intended for ease of tightening and not for looks.

Have you anodised the cylinder heads? They look great

Chatterbox / Re: True Engineering Skill
« Last post by pgp001 on Today at 10:47:04 AM »
I fully get where you are coming from with this.

I work as a design engineer in a manufacturing company, and I have a steady flow of machinists and fitters coming in to the office telling me that they "cannot" do something that has been designed.
In reality what they mean is they "cannot be bothered" to do it because they might have to do a bit of work for a change.
Our machinist has some really nice semi CNC lathes and milling machines etc, and he gets a bit miffed when I go down there to show him how to do his job.

Glad I am now counting the weeks up to retirement, I have had my fill of it now after 33 years.  :ThumbsUp:

Where in N Yorks are you by the way, I am just over the border in W Yorks.

Your Own Design / Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Last post by Vixen on Today at 10:35:11 AM »

"Can you see what it's going to be yet, Ralph?"

It's going to be a big pile of swarf and a little bit of metal left.  ;)

Would be interesting to know what the before and after weights are.

Well... the block started off at 1.37Kg (that a little over 3 lb) so there is plenty of potential for a big pile of swarf. You will have to wait for the finished weight.  :LittleDevil:

Achim, I did not go for the option where the dealer knows whats hidden inside. Instead I went for the cheaper "Kinder Surprise" option and will need to peel all the metal away to find out whats inside. Sometimes I am lucky and a nice engine part is hidden inside. Sometimes, there is only a useless lump of misshapen metal.

You pays yer money and takes yer chance.   :lolb: :lolb:

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