Unrebuilt bulleid poor haulage ability

Discuss Hornby Model Railway products and related topics here. This includes (Lima, Rivarossi, Jouef, Electrotren).
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markS&D
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Joined: Fri Oct 14, 2011 9:16 pm

Re: Unrebuilt bulleid poor haulage ability

Postby markS&D » Sat Sep 30, 2017 9:03 pm

Bigmet wrote:Best to make the rear driven axle fixed in my experience.


I agree with this, or even better, have the front and rear drivers fixed, have the motor drive the front driving axle, and mounted with its body in the loco's smokebox, there is then room to put plenty of weight over the driving wheels, and have the center axle lightly sprung, so that there is no chance of weight taken off the driving wheels.

That's my theory anyway.

Bigmet
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Joined: Tue Aug 14, 2007 2:19 pm

Re: Unrebuilt bulleid poor haulage ability

Postby Bigmet » Sat Sep 30, 2017 11:58 pm

End axle driven and sprung centre axle is my choice on RTR OO six coupled mechanisms. For repowering older models I have standardised on the Bach chassis that have this arrangement wherever possible, for its contribution to reliable pick up (3F Jinty, 56xx, 57xx).

Our slipshod model railway press paid no attention to this good feature, and Bachmann only went and dropped it...

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markS&D
Posts: 182
Joined: Fri Oct 14, 2011 9:16 pm

Re: Unrebuilt bulleid poor haulage ability

Postby markS&D » Sun Oct 01, 2017 8:28 pm

It is a good method, and with kit built loco's, that use an etched gearbox, vertical compensation can be employed on the center axle even if the center axle is motor driven.

I did used to own a Bachmann Jinty, and found it was a superb runner, even on insulfrog points, with its sprung center axle.

I do think that it is a bad idea when one of the end axles is sprung on a 6 coupled loco for the simple reason that if the spring is too weak it will lift the axle at the opposite end off the track, but if the spring is too strong, the center axle can lose traction. Plus on the Hornby bulleids, it causes the rear driving wheel to oscillate, quite badly on some examples.


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