Tich Motion Work

[mackintosh]

Hello fellow sufferers.
I am building my first loco a Tich, all was going well until today. I have drilled the cross heads and connected the pistons and fitted the motion brackets to support the guide bars and it's all gone tight. The motion work before this was very smooth even with the axle pump connected. The pistons move in the cylinders well and I can feel the "O" rings rolling when the direction is changed. The cross heads run smoothly. I can't get my head round the problem. ANY IDEAS?. Oh the motion brackets are spot on to the dimensions LBSC specified to position on the frames. Am I panicking should the motion work be stiff. I don't want to start on the valve gear and have to back pedal later. Here's a few pix to show where it's at.

[waggy]

Hi Mackintosh,

Don't panic!

Try each side separately, only one may be tight. I would suggest the piston rods are binding in the cylinder end cover or gland. You may have drilled slightly off the centre line of the rod. The easy way round this is to shim the slide bar, up or down. Shims may only be required at one end, it's a trial and error job.

Good luck,

Waggy.

[baggo]

Hi Bob,

I'll second Waggy's suggestion that it may be one or both slide bars slightly out of alignment that's causing the problem. I had a similar problem with Helen. As he suggests, try one side at a time instead of both at once. Disconnect the connecting rod and see if the cross head still moves freely. If you haven't pinned the rods into the cross heads yet it's worth rotating the piston/rod assembly relative to the cross head as often they are tighter in one position due to slight eccentricity of the piston on the rod.

John

[jgb7573]

Hi Bob,.

The only thing I'd add to Waggy and john's comments is that shimming is very common at this stage. It's frequently part of the fitting process.
By the way, what you've built is looking good!
JohnB

[standardsteam]

My Tich motion I could barely rotate once all fitted together, I pronounced to club members that it would never work. On trying on air, my expectations were realised until I wondered where all the air was leaking out. On putting a ball into the oil clack the thing sprang into life and became smoother in time. I made off centre bushes for my coupling rods. My worst part was a non concentric gland which acted like a friction nut on the rod. Watch the clearance on the brake hangers if you fit them. I used a countersunk screw on one of the cylinder cover bolts. (edit: doh - you have fitted them! I had to put chamfers on the beams to clear the flanges when up tight)

[mackintosh]

Thanks for all your help and encouragement you were right. I removed both cylinders first to see how free they were. They both felt spongy at times, suddenly clicked on I had well oiled the valves on assembly and this was the cause until they lifted there was resistance. So I removed them. This then let both units to move smoothly. I then mounted one and the stiffness returned, so I loosened the screw fastening the guide bar to the motion bracket, causing the smoothness to return. After some trial and error 5 thou sorted it. The other side was OK.
Thanks once again
Bob

[spurley]

Hi Bob

I was going to suggest that there may have been some 'vacuum' effect from the slide valves! I remember being a bit miffed about mine until I connected everything up and then the valves worked as pressure reliefs. I would second the bit about running on air and also what a great pleasure it is to be able to see something positive after the work put in, just wait and see! For the fun of it I have made some temporary steam chest covers for my Tich which I have in place for air running and demonstrations see images.

[ftp]http://modeleng.proboards20.com/index.cgi?action=display&board=general&thread=1158312665&page=1[/ftp]

Keep up the excellent looking work.

Cheers

Brian

[mackintosh]

Hello Brian
I've had a look at your pictures they are superb. I like the perspex valve chest covers. Did these help in setting the valves or was it just a case of I would like to see what goes on in there?. When you say running on air I assume a fitting was made for the steam pipe to connect to a compressor. What sort of time did you run it for and what pressure did you run at? Sorry for asking so many questions but I do find it most interesting.

Bob

[spurley]

Hi Bob

The perspex covers were more for interest than anything else but they help to show equal valve travel, port opening etc. It also helps those poor souls who sometimes ask me how a steam engine works and then then get the full 'nine yards' and a practical demonstration!

I have a small B&Q nail gun compressor which I use to run this on which came with a set of tools including a 'flatoscope' (tyre inflator adaptor and gauge). I have found that the inlet steam fitting size is the same as the tyre valve stem so the pipe simply pushes into the adaptor and clips on. I have managed to get the engine running on as low as 8psi (indicated) and the cut off notches work too even though air does not react quite the same as steam (no expansion as such).

Since those photos were posted I have completed the boiler [ftp]http://modeleng.proboards20.com/index.cgi?board=Images&action=display&thread=1163976013[/ftp]and it has been hydraulic tested by me and at my club. I have made the smokebox and the boiler is fitted in the frames. Next jobs are the regulator, main steam pipe etc and all boiler fittings to enable a steam test. I think I shall try to do this before final completion, tanks etc.

Cheers

Brian

[Shawki Shlemon]

Nice neat job on the boiler Brian . Was the the boiler code any good ?

[spurley]

Hi shawki

The code looks to be a great reference document, I had this boiler finished before you sent me the code but I have since had a read and it's 'good gen'!

Cheers

Brian

[mackintosh]

Hello Brian
I've checked out your boiler pix it looks a sound. quality job, well done. I have also been building my boiler as I have been going along, just as a change once in a while. It's had two visual inspections by our boiler inspector and is now ready for the final cook up. I am hoping to get the expansion brackets and the final decision on the type of safety valve sorted first. I changed the design slightly with the blessing of the boiler inspector and used a piece of 2 1/2" 16swg tube for the barrel with a split joint ring arrangement between the barrel, outer wrapper and the throatplate. I have some pix's if you are interested?
Bob

[spurley]

Hi Bob

I am certainly interested and I'm sure others would be too.

Why not start a new thread for your boiler? Don't put it too near mine in case you show up my workmanship

Cheers

Brian

[mackintosh]

There is no chance of that Brian. I will start a new thread as you suggest .
Bob