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I am inclined to agree with Adrian on the Hattons 4 and 6 wheel coaches.

When we at MROL ran the annual 'wishlist poll' a few years back (we ran it for 7 years), our observation was that the majority of modellers modelled a sliding window period of around 40 years behind the current date up to the current date.

That places most modelling as representing the mid to late 60's to the mid 70's period. By this time, all 4 wheeled and 6 wheeled coaches had long since disappeared from passenger services over 30-40 years before and any that was still extant was the last, being disposed of out of engineering stock.

What this means is that the vast majority of us probably have layouts where 4/6 wheel coaches will be well and truly out of period, unless one models one of the pre-nationalised companies or a 'preserved' scene.

It amuses me that we are probably going to see many layouts completely inappropriately running large numbers of 4 wheel coaches alongside latter day BR steam!

I guess that may rock some people's boats, but not for me.

Personally, I think Hattons would be better off investing in something else such as coaching stock for one of the big four.
 

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QUOTE (34C @ 23 Jan 2020, 07:01) <{POST_SNAPBACK}>So how did Bachmann pull off this feat then, with scale diameter wheels and a correct body plan form, on these and several other models
where the wheel tops are inside the body, and thus liable to foul on below scale radius curves?

I always thought (perhaps incorrectly) that Bachmann didn't pull this feat off and were using under-scale wheels on their Deltic. I don't have one to be able to check and will stand corrected.

To be honest, I really don't get the fixation with 'second radius'. Any bogied item is going to have massive end overswing to the point of being totally unreallistic in scenic areas.
I 'get' hidden sidings etc but even then, I'd question such tight radii as in hidden sidings, I would be looking for reliability wherever track is not easily visible.

If I had to resort to 2nd radius (or even 3rd radius for that matter) I'd seriously be thinking about an end to end layout in 4mm. Or moving to a 7mm scale end-to-end.
 

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QUOTE (34C @ 23 Jan 2020, 18:30) <{POST_SNAPBACK}>They got it right on their production Deltic, class 55. Too tall as supplied, so that the body clears the wheel tops going round R2. A few
minutes to drop the overall height to scale and there it is, all correct. (Reversible too, a washer on each of the bogie towers restores the
R2 capability if required.) That's the clever way, provide a path to a good scale model.

Unfortunately they went the undersize wheel path on the prototype DP1 produced for the NRM, and it really shows.

The washer approach on the production model is probably the best of both worlds: those who want to run on train-set curves can do so, but have to compromise with the height being increased and those who use proper large radii can lower the model down to correct it.

It is quite possible that DP1 was a completely different toolset, hence the results are different.
 

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QUOTE (34C @ 28 Dec 2020, 22:38) <{POST_SNAPBACK}>How does yours run? A fairly consistent report is emerging that the gear ratio used is inappropriate, basically too small a reduction ratio: so that the model has way overscale maximum speed, and is unable to move smoothly at dead slow speeds, and jerks into and out of motion. Potentially an easy problem for Dapol to fix, if they are so minded...

I have the same problem of jerky starts and jerky low speed with the Dapol class 22 Diesel Hydraulic. Strange thing is that it does this both on vanilla DC (with blanking plate and no decoder) and DCC (ESU Loksound 5) and it is worse in one direction than the other. Clearly a mechanical issue, not electronic. Have even replaced the motor with a new one and it made no difference. I suspect that the problem is a combination of the gear ratio being too high and the motor not being physically capable of running slow enough without jerking.

Kinda puts me off buying any other Dapol 00 locos as this isn't the first loco of theirs I have had with the same problem.
 

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QUOTE (34C @ 30 Dec 2020, 20:18) <{POST_SNAPBACK}>...From what I have read reported a major problem is the pick up off the split axles, and modification to wiper pick up has made good out of poor runners;...

I missed this little 'nugget' of information the other day.
One way to test this on the workbench would be to attach a wire to the rails and directly to the track pickup connections on the motherboard, bypassing the pickups completely.
I'm going to give it a go, but I don't think this is the problem.
My Dapol 22 is much more jerky at low speed in one direction than it is in the other direction.
The jerking is consistent with movements of the motor armature which suggests to me that the gear ratio is too high for the motor at low speeds such that the motor is not capable of running slow enough to make the loco run smoothly at low speeds.
Another option might be to source a completely different motor such as a Heljan or Mashima. Will be good fun trying to fit them...
 

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QUOTE (34C @ 7 Jan 2021, 22:49) <{POST_SNAPBACK}>I'll await your findings with interest!

The only Dapol twin bogie model I have really followed in terms of mechanism performance was the class 22, because I anticipated that much of that model's arrangements might be shared with the class 21. It didn't make happy reading, and a glance at the reports of the Dapol 52 and 73 had much in common. Jerky at low speed in one direction only was a regular problem, and I never read a fully satisfactory diagnosis. The closest to an explanation was circuit board malfunctions, due to poorly installed components/component failures. But no one 'went for it' completely bypassing the circuit board to check the effect of direct DC supply to the motor terminals; either returning the models for refund, or sending them to DCC Supplies as the repair agent for rectification.

(So far so good with my sole example of a 21, and that's been generally true of online reports as well, so Dapol may well have got it right with their manufacturing partner this time.)

I haven't tried bypassing the motherboard on the 22, but I did on the 41 which has Dapol heritage. The problem with the 41 is that it has a motor which is totally unsuited for the job. It runs great on DC control, but it totally unsuitable for DCC or feedback control. Bypassing the motherboard makes no difference. The stupid motor in the 41 managed to burn out a Loksound 4 for me - that's how unsuitable the motor is.

Bypassing the 22 motherboard can also be achieved by connecting wires to the rails directly to the motor, but absolutely critically, removing the decoder before I do it so as not to back-feed and damage the decoder.

To be honest, I think the problem with the 22 is the grearing ratio. I think that it is too high relative to the slowest speed that the motor is capable of ie the motor is not capable of running slow enough and when it does run slow, it is right on the boundary of jerkiness. It doesn't take much speeding up for the jerking to disappear.

I have contacted DCC supplies about this and was told that they had never heard of this problem. I also purchased a replacement motor from them but it made no difference.

I think there is also another dimension in that my definition of smooth slow speed running is somewhat tighter than what most people would accept (I'm very fussy about this). While most people tend to operate 28 speed steps and yank a throttle up to 10 to start, I prefer a more refined start with 128 steps.
However, I have noticed that the jerking is visible on some people's Youtube videos (even if they can't see it and they profess in the video 'this lovely smooth running'), but not all, so it seems to me that the jerking is not across the board.

Will report on progress...
 
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