Hornby M7 tank R2840

Discuss Hornby Model Railway products and related topics here. This includes (Lima, Rivarossi, Jouef, Electrotren).
muggins
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Hornby M7 tank R2840

Postby muggins » Sat Nov 23, 2019 2:37 pm

I have acquired for a very decent price a very nice secondhand Hornby M7. Now, I did realise before I bought it that it wasn't going to be able to pull much of a train, but even so, skin ... rice pudding ...

All I want it to do is get round 90°of 32" radius bend on a 1:44 incline with one ordinary free-running carriage behind it without showing signs of wheelslip. Is that really asking a bit much, or is there perhaps some fiendish wheeze which might improve adhesion?

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Alexander Court
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Re: Hornby M7 tank R2840

Postby Alexander Court » Sat Nov 23, 2019 2:55 pm

Perhaps someone removed the weights in the tanks for some reason. When I had the LSWR 252 one I found it worked better with lighter trains but generally struggled to climb anything other than a gentle incline with anything, its driving wheels were very slippery on the rails sometimes.

"I love the way you call it Art, When you never even use your Heart, and I just wanna tear you Apart"

muggins
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Re: Hornby M7 tank R2840

Postby muggins » Sat Nov 23, 2019 3:02 pm

Ah, that's one thing I can check then. Thank you for the suggestion.

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SRman
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Re: Hornby M7 tank R2840

Postby SRman » Sun Nov 24, 2019 1:00 am

Weight distribution can be a problem with these locomotives, as well as a lack of weight anyway.

I have plans to eventually replace the tank weights with real lead - the manufacturers aren't allowed to use this any more, but we can.

Also, check that the balance of the model is as correct as you can get it. I found one of mine tended to lean back onto the rear bogie, meaning there was almost no weight on the front driving axle. A piece of springy metal threaded over the pivot to lever the back up slightly (but not too much) helps here, but may need a bit of fiddling to get it right. Alternatively, a small plastic washer can space the bogie down a bit (or body up at the rear).

Ultimately, some extra weight in the front of the boiler would help a lot, but the decoder socket gets in the way of this. If you are really brave, you could remove the socket and rewire the loco. If you use DCC, hard-wire a decoder but locate it further back, possibly in the bunker if there is room (I haven't looked), or on the cab floor.
Last edited by SRman on Sun Nov 24, 2019 7:29 am, edited 1 time in total.

muggins
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Re: Hornby M7 tank R2840

Postby muggins » Sun Nov 24, 2019 6:38 am

Thanks SRman. I'll open the patient up as soon as I get chance and see what I can do ...

Bigmet
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Re: Hornby M7 tank R2840

Postby Bigmet » Wed Nov 27, 2019 10:46 am

Simplest thing to try is how it does running in reverse, this being the normal direction of 50% of the running of a tank loco. The torque reaction throws more weight onto the coupled wheels. (It may do better yet running in reverse and pushing the coach rather than pulling.)

Although it is a very lovely model to look at, Hornby got the mechanism layout wrong. Forward of the rear coupled axle it should have as much weight as possible, the motor should be in the firebox, driving the rear axle, and lightweight tackle like the decoder socket should be in the ample space of the bunker. (We'll see if Bachmann do better when the MR 0-4-4T comes out.)

For all that, it can do very well on dead level track, up to 12 Bachmann mk1s can be realistically moved. I had to fiddle with the pick up wires to the bogie which supply some springing, and adjust the pick up wipers on the bogie wheels to 'barely rubbing' to achieve this. Performance drops off a cliff if there is a gradient, because of the balance issue that comes with this configuration.

muggins
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Re: Hornby M7 tank R2840

Postby muggins » Wed Nov 27, 2019 11:12 am

Cheers Bigmet. All that makes perfect sense, so a full astern pushing trial is now #1 on the "to do" list.


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