Trunch Trojan

Hi I am just setting out on my first project the Trunch Trojan by Bob Middleton

If there are any members who have completed this or part way through PI would love to hear from youm

For instance he says 2 of for the slide valve when only 1 will fit.

Sticking with the slide valve, the way it is drawn it would have to go upside down which would be silly.

I, m not knocking Bob, far from it he's done a great job designing it but it's frustrating having to 2nd guess his drawings.

Any help would be much appreciated.

Newbie

Hi Arthur,

Welcome to the forum, afraid I haven't come across that design.

<edit> Looks like he cut a double engine in half, and only drew the extra information for teh single version, so some of the drawings refer to the double version.

Neil

Edited By Neil Wyatt on 11/04/2020 12:59:31

Neil is right the valve drawing has just been copied & pasted from the double but hopefully this engine will only half the errors I've corrected a few errors on his other designs that have appeared in ME for Diane and Martin so there probably are a few in this one as well.

If you look at the metric version that Julius did that just shows one valve and the position.

Thanks that explains a lot.

Arthur

Hi all

Further to the slide valve on the T. T engine I have today made this valve and along with the other components now have a better idea of how it works.

One thing puzzles me though, with ref to J. A. M. De waal, s excellent cad drawing the slide valve sits on top of the valve rod (2-09.4) and presses up against the underside of 1-06.3.

When the valve slides it will expose one slot and cover up the other. This I understand as it will stroke the piston up and down. What I fail to see is what function does the pocket on the top side of the slide valve do?

Any ideas?

The pocket acts to connect the central exhaust passage to the "inlet" that is now on the emptying side of the piston so allowing the used steam to be exhausted.

Edited By JasonB on 12/04/2020 18:21:33

Very clever. Would never have worked that out.

Thanks for that

Hi all

Have today successfully completed element E of the T. T 1.06 IN The cad drawing.

Tomorrow will be my biggest test since starting this project.

I need to deep drill a 3/32 hole 2.25 inches deep, passing through the pocket to the far side and carrying on for a further9/16.

I need to maintain accuracy along the center line and also to be parallel with the face.

This is so when the valve rod and slide valve are fitted that the top of the slide valve is a snug fit on thr underside of element D (106-3) which contains the steam portsm

Any advice would be greatly appreciated.

Thanks

Forgot to say will be doing this on my mini mill with the drill in a chuck as I have no collet small enough

Cheers Arthur

If I were doing it I would drill and ream the 1/8" hole first then use a long series ctr drill to start the 3/32" hole on the far side of the valve chest. If you don't have one you can make a simple punch from a length of 1/8" silver steel.

It's not usual for the valve to be a tight fit against the port face, a bit of float will allow the valve to lift if condensate builds up at the ends of the cylinder and is pushed out, if not you may get a hydraulic lock.

Thats a gteat idea thanks for that.

Have got some silver steel on order.

Will let you know the result.

Thanks once again Arthur

Hi all

Just to let you know I completed my deep hole drilling successfully thanks to Jason, s sage advice.

I am now into element "a" the cylinder head component. Neither Bob M, s version or the cad version show the piston rod gland threaded on the 3/8 dia (1-08.4) and only Bob M shows its mating hole threaded.

I lean towards J. D. W's version as he as elongated the 3/8 dia and included the seal material, relying on the 2 studs to hold the gland down and compress the seal.

Am I correct in this assumption.

Regards Arthur

I would say Bill's note to tap the 3/8" hole is wrong, two studs with nuts and locknuts allow you to adjust the compression of the seal and lock its position.

Some engines do have a threaded gland but they would typically have a knurl or hex so the gland can just be screwed down onto the sealing material not the oval shape with stud holes.

Thanks for that.

Your help is greatly appreciated.

Arthur

Hi All

Been making good use of the lockdown to crack on with my engine (every Cloud.......)

Now at the stage where I am ready to do a test build of the cylnder and its constituent parts.

It is made up of 6 seperate components all 2.25 diameter (or thereabouts)

What I would like to know is, what is the preferred gasket material for a steam cylinder and what thickness should I be looking to use.

I have scanned other forums and the variety spans from using a dollar bill to brown paper and oil

I will be including some pictures on my next post of the parts and completeed cylinder,

Regards

Something thin like brown paper is good to avoid changing the dimensions too much. Instant gasket is fine if you are not expecting to disassemble too often.

Proper gasket paper can be thick enough to cause pistons to lock if tolerances are close.

Neil

I use a liquid (instant)gasket on all my engines which effectively has no thickness when assembled so you don't need to make any allowance for it, get it from the likes of Halfords.

Hi Neil

Thanks for your answer.

When you say proper gasket paper, what thickness ate we talking about.

Arthur

Hi all

Not got round to assembling the cylinder as Ineeded to prrpare the base for it.

This is were I hit a problem. The base measures 7.5 X 3.5 inches, when I mounted it to my face plate and centrslised for the counter bore, the throw was 6.5 inches and fouled the bed. My lathe is a 5 inch denford.

The only way forward was to saw off 1.5 inch.

Now looking at this with hindsight (a grrat thing) what i should have done was make the steam chest cover the same diameter as the S C and use the same bolt circle to fasten them both dowm see pics.

Any reason why Bob would not have chosen this option?