Jenny Wren

[olympic]

First engine I ever made, and it even runs. From a plan by Tubal Cain. 1/8" bore by 1/8" stroke.

 

[Norris]

I just watched a video on youtube showing one of these engines running and I was so impressed I bought Tubal Cain's book so that I can build one!!!

 

[Cogsy]

Very nice build. Any chance of a video?

 

[Blogwitch]

Very nice indeed, well made.

Engines like this lend themselves to making just the engine itself that can be run on air.
I took the basic dimensions of the engine and made one that was free standing to go on my collection shelf.
You can do this for almost any of these engines that come with a boiler, very good to have if you don't fancy making the boiler. I had made one many years before exactly to plans, unfortunately, it was given away soon after I finished it. This one is a keeper because it takes up no room at all.

The crank was made from a single piece of silver steel

Done in a largish 4 jaw.

The finished item

The baseplate was a 1 euro coin.

Plus it runs very well.
The main problem was getting an airline to fit, I ended up using very small silicon tubing purchased from a fishing tackle shop.

So here is a video of this engine running



So don't forget, you can use almost any part of a set of plans to get whatever you want.

John

 

[olympic]

Love that crank, John. I think I'll try that for an even smaller engine I want to build: 1/16" bore and stroke. It's the Janes Senft "Thimble Engine".

 

[Blogwitch]

Olympic,

I have seen pictures of that thimble engine, a very nice (but small) project.

I don't think I could make one that small nowadays, eyes and nimble finders aren't there any more.

With reference to the crank, I think that was done using an 8" independent 4 jaw on my old Atlas 10F lathe, and it does prove that if you think things out, you don't need tiny machines to make tiny parts, just very sharp tools.

Good luck with it

John

 

[olympic]

Thanks, John. I've already made the thimble boiler, fuel tank, and stand, the piston and cylinder, the flywheel, and a built-up crankshaft using a 10-inch Logan lathe, so the size doesn't daunt me too much. The crank doesn't run quite true, though, so I'll try to turn one.

Actually, the biggest trouble I'm having is accurately locating the holes and ports

in the tiny engine standard, but I recently acquired a Cameron precision drill from an estate, so I think I've got that problem beat now, as long as I save the Guinness till I'm finished drilling....

 

[Blogwitch]

What a lovely bit of machinery you have there, I have all the castings to make a similar machine, but I doubt if ever I will get around to making it.
I think all yours need for precision work is to get a tiny X-Y table on it and a good magnifying glass.

I also have a precision drill, and I mounted a mag chuck onto it to allow me to move something into position then lock the tiny vice or holding fixture down for drilling.

One thing I will suggest is to get yourself a couple of spot drills instead of trying to put a spot on with a small centre drill. Spot drills allow you to make tiny little indentations, smaller than even a centre pop mark.

Once you have that centre mark it is then just a matter of mounting it centrally into your 4 jaw and gently turning it down.

Keep up the good work, and show us how you are getting on. I think people have more problems making tiny bits than they do with large ones and every bit of help that can be given to show how it is done really helps.

John

 

[olympic]

Thank you once again, John.

I just received a tiny XY table, so that's taken care of.



A small mag chuck sounds like a good idea; I'll look into it.

Finally, I'd never heard of a spot drill (I have absolutely no technical background, being a bit of a Latin scholar ) but again I'll look into it.

 

[Blogwitch]

Olympic,

Not from your country, but this is where I get my spot drills from (only the cheaper type), on pages 2 and 3. The smaller ones are my usual working ones as I can see where they are going and give a perfect spot mark for drilling.

http://www.engineeringsupplies.co.uk/advanced_search_result.php?keywords=spot drill&sort=5a&page=2

They became very scarce and expensive a few years back but they were then resurrected for CNC work because of their accuracy over centre drills (which should only be used for putting in a centre shaped hole for tailstock support or between centres turning) and the prices have dropped dramatically.
You can buy replaceable tipped units that are very good but also very expensive. Ok if you are doing thousands of spots a day, but for our use, the cobalt ones are perfectly adequate for doing the job perfectly.

I hope this helps

John

 

[olympic]

I found some spot drills and have ordered a couple of the smaller ones.

Thanks for the tip, John

 

[fcheslop]

For drilling the ports on the thimble engine its easier to make a jig
Its possible just to use 10 or 11ba thread for the pivot
For the crank shaft and big end pin I used the shanks of the drill bits and they fitted well or maybe I was just lucky
Make enough material for several tries for each part as you may need them and it saves going back to step one every time
They sound like an angry wasp when running

 

[olympic]

I've managed to turn the cylinder and its pivot in one piece, even on the 10-inch Logan, and I've threaded the pivot internally 000-120. A 000-120 screw with a spring on it will eventually hold the cylinder against the port face. Tiny stuff!

My not-so-straight crank was built up using shanks from broken drill bits; I'm going to try a one-piece crank for the sake of greater accuracy.

I've made three or four of everything so far, and even so I may have to make another cylinder because I'm not happy with any of the ones I have....