hornby thompson

[hedgefordpete]

hi everybody, purchased a new hornby thompson tank engine to use as a shunter. what a disappointment. the front pony wheels run sideways around the curves and jump every set of points on the layout. ok in reverse.
i have tried a thin wedge of thin cardboard and now i am running with a ball of bluetack to hold the wheels down on the track. i think that there is not enough spring to hold the wheels down and they just float about.
is it me or is this problem known to anyone else.
regards, pete.

[6C]

Not uncommon, fortunately 2 solutions - 1 easy and the other more involved but still straightforward.

1) Wheel back-to-backs - some just needed this checking and opening-out slightly - as they were a little narrow for the trackwork

2) Only try after the above - the pony truck itself is a strange design and incorrectly sprung (undersprung) - it need extra weight adding directly to it (tricky to find the space) - or a mechanism to 'hold' down the pony truck onto the rails - some have botched up methods user strong copper wire angled to push down on the truck.
I have seen in another place - an excellent mod whereby, the front pony is tamped down by a strong piece of wirewhich is then passed through the pony and secured by the first chassis screw, google 'Thompson L1 pony' and you should find an image.

Mine BTW has not needed either - so unlucky there - but it does look strange in it's behaviour and direction through pointwork.

[Bigmet]

It's not a good arrangement at all, shame that they used it on what is otherwise a very classy model. The real problemis that the truck doesn't straighten up immediately after leaving a curve, makes it very prone to tripping up on points. Fixed mine by converting it to single pivot. (Hack away the two bumps on the keeper plate, and the kidney shaped holes these engage in on the pony truck, drill hole in pony truch rear, use small self tapper into keeper plate to make new pivot.)

Strangely, the Thompson O1 also has the very same design truck and yet my example was trouble free, straightened up pretty quickly on coming to straight track. Wasn't quite perfect but WAY better than anything I had seen before on my 8F and L1 chassis. Very interested to discover why, and it is down to the shaping of the kidney shaped holes in the truck which should produce the intended camming action as the truck swings. The centre of the kidney shaped holes is narrowed quite significantly (more so than on the trucks of other two loco types), and by bending the metal a little to make the hole a very little narrower yet it became perfect in its tracking.

[hedgefordpete]

hi, thanks for the interesting advice , I will have another look at the problem and see what I can do.
regards, pete.