First loco – advice needed

[Bob Oliver 1Participant @boboliver1]

Inherited a part-built 'Tich' (chassis, running gear and cylinders all erected). Bought the plans and LBSC book and took it to air running stage. Started in reverse at 2 psi but needed 25 psi to start forward. Once running seemed OK but always stopped sharply. Clearly binding in the motion. Assumed a problem with 'quartering' or coupling rod lengths. Stripped it to component parts, checked chassis and wheel dimensions and axlebox and axle alignment (all to plan), made new springs, crankpins and coupling rods, paid careful attention to quartering the wheels and erected the running gear. Still significant binding at two points on each revolution. Stumped now. Any suggestions?

[Bob Oliver 1Participant @boboliver1]

Running gear binding despite much headscratching

[Another JohnSParticipant @anotherjohns]

Bob – my large boilered Tich works wonderfully.

The state of it when I started running was that it was too tight – wheels would barely turn when forced.

After first successful run (coal firing is a "learning experience" on such a small fire) it was free, and has been so since.

It is wearing out, but runs better than ever. Looking at the slip eccentric in depth, and I was amazed at what 20 years of running did in terms of wear, but, the little Tich still goes!

I love these little engines; keep going and hopefully it will be your cup of tea, too.

John.

[nigel jones 5Participant @nigeljones5]

I had same problem on the 71/4 invica i am just completing. I remade most parts 3 times until i worked out what was wrong. The mill head was off centre by a fraction. When measuting on the surface all dims were spot on but as soon as you inserted the link pins it went way out at each extreme. Worth checking as it nearly drove me to quit!

[Boiler BriParticipant @boilerbri]

Hi Bob, are all the pins in the wheels at 90 degree to the bore of the wheels?

Bri

[Neil WyattModerator @neilwyatt]

> Still significant binding at two points on each revolution. Stumped now. Any suggestions?

If reverse is OK, perhaps the problem is really with the valve gear? Is it slip eccentric or stevenson's gear?

Axles not truly parallel? or perhaps you need to replace springs with spacers so the suspension is in its 'loaded' position.

You may find that easing one or more of the hornblocks might help, a little and free running rattle is better than perfect fit and no joy.

Also, is it possible the left and right hand connecting block have been swapped over.

[julian atkinsParticipant @julianatkins58923]

Neil,

if you have a look at Bob's pics his Tich has Walschaerts valve gear.

if it runs ok in reverse on 2 psi, then i suggest it is a valve setting problem. Bob, you need to take off the steam chest covers, accurately work out and mark FDC and BDC as per the well known procedure, and check that the valve is as central/equal leads in forward as it appears to be in reverse. i suspect a problem with the return crank and eccentric rod length, giving ok valve events for reverse but wildly out for forward.

also check clearances with the radius rod slots etc.

cheers,

julian

[Bob Oliver 1Participant @boboliver1]

Thanks to all who responded. I used your advice and found that what was needed to overcome the binding was some easing of the hornblocks. It seems odd to have to build in 'slop' but it seems to be the answer. Re-assembly now progressing and I shall be following your advice when I get to the valves.

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