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Hornby T9 Motor Meshing Problem

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I have a Hornby T9 class R3107 (No 30313) whose running (which has never been exactly quiet and smooth) has deteriorated to such an extent that I was compelled to investigate further. 

 

I removed the motor, retaining bracket and rear piece and both show no apparent signs of distortion or damage due to Mazak rot. On reassembly, the motor worm fails to engage satisfactorily with the intermediate gear wheel; hence the source of the rough running. It is as if the single fixing screw at the rear of the assembly and the two locating lugs at the front are insufficient to keep the motor aligned and that further support is needed to keep the worm engaged. The gear wheel (cog/pinion) is in good order with no teeth missing.

 

Replacement bracket pieces are available from Peter's Spares but as the originals appear OK I don't see the need to replace them.

 

Any helpful suggestions would be greatly appreciated.

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Has one of the intermediate shafts worn the mazak away, allowing it to slip out of position?  I've just had that happen on a Hornby A4, whereby the intermediate gear was allowed to ride up and lose mesh with the driving axle.  Also, check none of the (tiny) wires has slipped into a join and is preventing the part from seating correctly.

 

I've had to rebuild two T9s with the brass replacement from Peter's Spares and it is a much better arrangement.

 

Also, just as an aside, are you sure it is this which is the problem?  One of ours had become a poor runner over a long period, despite a replacement motor and it was eventually found that the wires from the front bogie had frayed and the insulation had worn through, so the thing was shorting on a permanent basis.

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Thanks Jwealleans. It's definitely mechanical. If pressure is applied to the top of the motor, the worm meshes with the gear wheel but the fixing screw alone is not having any effect. I suspect this is a wear issue and the solution will be replacement parts.

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The flaky mechanical design of the front clamp cum worm cover on this and the other contemporary Hornby steam mechanism designs has led me to glue in the motors using Evostick. That completely relieves the clamp from taking any mechanical load. I have never had a T9 to look at, but on all those I have tinkered with there's a good contact area available between motor casing and the main casting to ensure adequate bond strength. Ensure the bond has fully gone off by 48 hours in an airing cupboard or similar warm location before attempting operation.

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I had a problem with a T9 and there were two issues. One as described above was the casting fracturing, stopping the gear mesh between the idler gear and worm. This was resolved with a Peters Spares replacement. The second issue I eventually discovered, was that the final drive gear had moved sideways on the axle, so losing contact with the idler gear. The centre part of the axle has splines which grip the boss of the gear. This I cured with a tiny spot of super glue, ensuring first there was no oil or grease present. Stripping down the chassis to get at the gear train isn't easy with tiny wires and pickups getting in the way. To be honest, it's a real pain, but with steady nerves and patience it can be resolved. It took me several attempts before I cottoned on to the loose final drive gear issue.

So if your loco motor spins happily, but the loco doesn't move, then you know now where to look!

 Have fun, keep the faith and your patience!!

 

Tod

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Just discovered this thread. If any of the plastic gears are slipping on the axles check for splitting. Sometimes there will be a definite 'clonk' every wheel revolution and the gear that has split is easily found. Other times the loose gear needs close inspection to find out if it has split.

 

Jim

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Ok, so I have a brand new GWR King that is noisy and rough at low speeds. Once it starts moving it smooths out. I opened it up and checked the wheels and gearing and it looks fine, no apparent flash and well lubed. The motor seems to be fairly tight in the mount. Do these have any history of the motor gear not meshing with the drive gears? Anyone else experience this issue with the current run if Kings?

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That has happened to me...on more than on occassion.

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On 17/06/2019 at 22:03, Cofga said:

Ok, so I have a brand new GWR King that is noisy and rough at low speeds. Once it starts moving it smooths out. I opened it up and checked the wheels and gearing and it looks fine, no apparent flash and well lubed. The motor seems to be fairly tight in the mount. Do these have any history of the motor gear not meshing with the drive gears? Anyone else experience this issue with the current run if Kings?

Followup—I tested the locomotive performance on DC with a MRC power pack, and in DCC using several different brands of decoders. The rough perfirmance was still there with the MRC DC unit which uses PWM in a manner similar to that used in most DCC decoders. In the end the SoundTraxx ECO-100 UK Steam decoder gave very smooth performance and a Digitrax decoder was not far behind. So I suspect this is a matter of the back EMF algorithm being different in each decoder and not working so well with the Hornby motor. This is the first time in 25 years of working with DCC that I have seen a problem this obvious but it is not unexpected as there can be a real magic to adjusting the BEMF PID controllers. Next I plan to do these tests with the Oxford Rails Dean’s Goods loco and see if the performance problems folks have complained of over the last 2 years can be traced to the same cause.

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My T9, 30726, was running rough and became prone to derailing over one particular bit of the layout. When I opened it up the motor housing and retaining plate had both fractured. 

Hornby have replace them free of charge as it was a known problem and I had the original receipt. Arrived back today and now runs better than when it was new, even over the points where it used to derail at times.

 

 

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