PM Research#1 Cylinder Can it be saved ?

Hello all, not sure if this the correct place to ask this question??

I think I might have "bricked" my little cylinder for my model PM Research #1

I was milling the small steam valve slots in the cylinder chest, basically blind milling due to the tight conditions, I was using my DRO as my reference, old rookie mistake, the cutter was not tight enough in the collet and it walked its way out making the slot to wide and protruded through into the cylinder bore,

My Question can it be saved?

I was thinking

JB weld?

Silver Solder?

Scrap bin?

any suggestions would be greatly appreciated

Thanks Gary

My Question can it be saved?

Yes.

No need for the scrap bin as an alternative, yet.

If filling the hole is not a sensible option, one could fit a liner.

Are you going to run on steam or air and if so will the engine just run for display or will you want it to work.

In most cases filling with JBWeld should do but if working hard at high pressure then a Sleeve may be the better option and that can be slipped in with Loctite 648

You will have to either remachine the inlet slot which now looks like it is too wide compared to the good one and may have a job getting a crisp edge to the JBW in which case machining out the whole valve chest deeper and inserting a plate would be the best cure

Also what's going on with the exhaust slot, that looks to be over length for part of it's depth so you may need to widen the valve to get a good seal at the edges or see plate mentioned above

If you make a slug of cast iron to fit the slot that you have milled it can be pressed in and if you hit it with a punch it will expand and will never come out. You have to make the plug a good fit and you have to have a piece of round bar in the bore of the cylinder to suport the bottom of the plug. You won't have to re-machine the slot if the plug is the corect depth. When fitted you punch the plug with a diamiter pin punch along its length and it will be permanent and won't move although you may have to skim the cylinder bore as the plug may stand proud a little. I have used this method in many castings both cast iron and aluminium to repair all sorts of machinery and tooling.

David

Look at the second photo the slot is much wider than the other as either the cutter has been wobbling about or more likely gone in beyond the parallel flute length and started cutting where it tapers out to the shank diameter so will be a tapered slot and need to be remachined.

Thanks Jason, A few options to consider,

And yer I mucked up my maths with the exhaust slot also, so for part of the depth the slot is a couple mm lone each direction.

Stupid day yesterday!

I would bore slightly oversized and sleeve the cylinder.

If you haven’t made the valve yet you can make it oversized to cover your ports.
The limit on flow will be the (presumably to do) drilled holes from the ports to the ends of the cylinder, so the imbalance in slot sizes shouldn’t affect the running much.

Dave

Might as well mill the ports out completely and put in a rectangular cast iron block with some loctite and start the ports again from scratch. Once the ports are corrected bore out and fit a liner.

By the time you've machined a recess, fitted a plug bored out the cylinder, made and fitted a liner, you'd have made a new cylinder from a lump of iron bar. If you are making a new one make the valve chest a loose piece, then you can see what you are doing when machining the ports

Just as a btw .... PM Research will supply individual replacement castings for a very reasonable cost.

(Ask me how I know).

Judgement call of course - whether to repair or replace - in this case I'd choose the latter if it were me and have another go knowing what you know now.

Edited By Peter Greene on 26/09/2021 18:02:34

Thanks Peter, yes is an option, and will probably go down the road,

Still might have a play around with the repairs, while I wait for a replacement.

Thanks for the suggestions and advice, lots of good ideas to think about,

Gary

Duncan I totally agree with you but the original poster didn’t mention buying or re making a replacement, he wanted suggestions to repair what he had messed up, I just offered an idea to put both the mistakes right. I would certainly favour a separate steam chest, makes life so much easier.

You're right of course.

The only thing is, it "looks wrong" when the other parts have cast surfaces and the cylinder is machined. That would be my take anyway.

If you have a look in my album you will see some photos of a similar situation. I had bought a Stuart 10V which had been well butchered. I had to machine out the inlet and exhaust ports and then machined a brass block which was JB welded into place. This worked very well.  The solution was shown in my Resurrecting a Stuart 10V series of posts.

Colin

Edited By Colin Heseltine on 27/09/2021 20:36:06

Edited By Colin Heseltine on 27/09/2021 20:36:42

I think the problem with that will be that once the individual plugs are slotted you will have some quite thin walled oval tubes which may crumble. Would be easier to mill out a rectangle and bond in one single block say 3mm deep.

Also when you come to mill the new slots check you don't have too much cutter sticking out of the collet as that may have been part of your initial problem trying to reach down into the chest, a long series cutter would be safer.

If it’s any consolation, the Blondihacks lady on youtube made the same mistake on her PM1, but didn’t mention it at the time. When attention was drawn to it in the video comments, she replied that it was “within specification’ !

(She also made a mistake with the height of the steam chest inlet and ended up catching the valve face with the tap when she tapped the hole.)