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raynerd:
haha, thanks again for your replies. MadJack - I`m along way from a vid of it running...but I`m about to go to bed so I guess I can dream!!

OK, well first problem this evening of my own doing! Despite reading through and even replying to Andy`s message earlier today regarding the length of the cylinder and the fact that the ports should be central to the length. I`ve managed to do a superb bore that I`m really pleased with and then I went and faced off the bottom but not taken quite enough off. I don`t know how I`ve done it as I`ve checked and double checked but I`ve pulled it off the lathe with 0.03" to come off the full length and then realised that will make it short on that side!!

The cylinder should be 1.125" length with the ports symmetrical. My cylinder is 1.155" with the ports symmetrical and centered!

So my dilemma is that I need to take .015 off each side but of course now I`ve done the bore and faced up the bottom side symmetrical to it, I can only remove material from the one side (the full 0.03”). I know for sure I`d mess up my bore if I tried to recentre it and I don`t have any more material left to centre and then take a few more skims to true the bore up ....

I know this isn`t ideal but for 0.03" too large cylinder, could I increase the piston rod by 0.03" (or would it be half of that 0.015" ?)

Advice appreciated.

Despite my problem, I do have a few pictures!
My Go-no go gauge I knocked up for testing the bore:

I don`t know why I`m putting this up as this is where I`ve mucked up!! I need 0.015” more off this side!!!

Despite being deflated with my muck up, I still wanted to mock up the sort of setup for truing up the steam face I`m going to use later on. This is what I was thinking – will remove the vice and bolt the angle plate to the table:

Anyway….I can`t go anywhere until I sort out this cylinder length. Any suggestions would be appreciated. It would be simple to take it to size, the issue is of course facing up true to the bore which of course should be done in one opperation.

raynerd:
Couldn`t sleep thinking about how I was going to correct this.

I have decided I can`t re-centre it, I just couldn`t get it accurate enough. I also can`t rebore it to bring it to centre, not enough material.

My cylinder is actually 0.03" too long. Would it be worth, as I suggested last night, leaving the cylinder as it is and increasing both the piston rod and the rod the works the slide valve by 0.015". This will bring the piston to the centre of the current cylinder, I`ll just have a 0.015" bigger gap than expected at both ends, but in my eyes, that won`t matter?? It`ll just stop it bottoming out ?

I thought I could take the 0.015" from the top side if I like but that won`t do anything will it, I`d still have to increase the piston and sliding valve rod lengths). If anything it is the bottom side (which is the faced up side which I can`t touch) that needs the 0.015" off then it would be to size!!!!

Advice would be much much appreciated! :( :( :(

Stilldrillin:
Chris,
I don't think the cylinder oal matters, that much. As long as the valve chest and cover can be made to match. :thumbup:

I think you may do more harm than good. If you try to correct it now. :scratch:

But! Who am I to give advice? I've never made one myself...... ::)

David D

NickG:
Chris,

I don't understand why you can't just skim 0.015" off each end?

Nick

matnewsholme:

--- Quote from: craynerd on October 07, 2010, 03:31:56 AM ---Couldn`t sleep thinking about how I was going to correct this.

I have decided I can`t re-centre it, I just couldn`t get it accurate enough. I also can`t rebore it to bring it to centre, not enough material.

My cylinder is actually 0.03" too long. Would it be worth, as I suggested last night, leaving the cylinder as it is and increasing both the piston rod and the rod the works the slide valve by 0.015". This will bring the piston to the centre of the current cylinder, I`ll just have a 0.015" bigger gap than expected at both ends, but in my eyes, that won`t matter?? It`ll just stop it bottoming out ?

I thought I could take the 0.015" from the top side if I like but that won`t do anything will it, I`d still have to increase the piston and sliding valve rod lengths). If anything it is the bottom side (which is the faced up side which I can`t touch) that needs the 0.015" off then it would be to size!!!!

Advice would be much much appreciated! :( :( :(

--- End quote ---

chris

2 methods spring to mind. Either clamp the face your sure is square to the bore down to your mill table,fly cut 0.015 off the other end (thus making it parallel to first face. then flip and take .015 off other end.
If you want to do it lathe then turn a scrap bit of bar in lathe so its a nice sliding fit in bore. without removing this bar from chuck put a couple of drops of super glue on it and slide cylinder on making sure you leave enough gap between back face and chuck to get a facing tool in. then face .15 from both ends. You may need to use tailstock support on the scrap bar to allow it to extend far enough out from chuck to get a facing tool down back of cylinder.

mat

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