Katier Posted October 11, 2011 Share Posted October 11, 2011 HI All, I've finally got round to finishing off my first kit which a 3mm/ft 3SMR J72 with 3SMR chassis. Power is provided by (well in theory) a MH1020/ MH1024 Mashima can motor attached to a High Level Models Slimliner+ three stage gearbox. The Gearbox on it's own seems to run fine, the chassis on it's own seemed ok (pushing along track - certainly no stickiness caused by quartering type issues).. Put the two together and nothing - the gearbox unwinds (motor isn't restrained and body is off) and then just locks. I'm using a 12v feed through a push to make switch to test with wires fed directly to the motor. Currently havn't installed the pickups till I'm happy it's running ok In short... HELP!!! (please) Kat Below are pictures of the offending article. Link to post Share on other sites More sharing options...
craigwelsh Posted October 11, 2011 Share Posted October 11, 2011 I assume you had washers in to control the sideplay and nuts on the centre crankpins for the actual test? The left coupling rod seems to have a slight joggle in it in the first picture too. Link to post Share on other sites More sharing options...
Katier Posted October 11, 2011 Author Share Posted October 11, 2011 nope all be it screwed up better the middle pins weren't screwed in.. The coupling rods are slightly warped but seem to run ok without a motor.. Related questions.. 1) washer between rod and wheel or rod and nut? 2) Assume I should use thread lock when it's all working? Link to post Share on other sites More sharing options...
RMweb Gold Happy Hippo Posted October 11, 2011 RMweb Gold Share Posted October 11, 2011 Have you tried running it without the rods in place? At least then you'll know the motor and gearbox are ok and the problem is further down the drive system. Regards Richard Link to post Share on other sites More sharing options...
Arthur Posted October 11, 2011 Share Posted October 11, 2011 Try moving the gearbox back from the jammed position, manually restrain it, preventing it lifting and flipping over, and apply some light power. Does it run then? Sometimes the first thing to rotate is the gearbox around the axle and with some gearboxes, High Level are amongst them, they can take up a position where they do jam. You usually need to fit some system to prevent this type of gearbox rotation, a simple brass strap over the motor will suffice. Arthur Link to post Share on other sites More sharing options...
brossard Posted October 11, 2011 Share Posted October 11, 2011 If things are locking, you could have a quartering issue although the wheels appear to self quartering. The coupling rods look warped to me which could mean they are under stress. Without motor and gearbox, but with rods on, the chassis should roll freely. If it sticks every rev, there's an issue. The coupling rod holes look tight to me and may need opening slightly - do this gradually with a reamer and keep trying until the chassis is free rolling. John Link to post Share on other sites More sharing options...
Katier Posted October 11, 2011 Author Share Posted October 11, 2011 Yes the wheels are self quartering and yes it runs fine just driving the center wheels. Manually restraining the motor doesn't seem to help. Link to post Share on other sites More sharing options...
RMweb Premium spamcan61 Posted October 11, 2011 RMweb Premium Share Posted October 11, 2011 Yes the wheels are self quartering and yes it runs fine just driving the center wheels. Manually restraining the motor doesn't seem to help. Looks to me like the coupling rods are slightly too long and hence are bowing, compare the wheel base with the distance between the coupling rod holes, they need to be identical if trouble is to be avoided. Link to post Share on other sites More sharing options...
Arthur Posted October 11, 2011 Share Posted October 11, 2011 So, with the coupling rods off the motor gearbox will drive the centre axle/ wheelset okay? Try running it as two separate 0-4-0's. You'll probably need to turn them upside-down first, put the rods on so that firstly you couple the centre and leading axles (with the rods extending forwards) and try that. Then couple the centre and rear axles (with the rods extending rearwards) and try again. If one works and the other doesn't you know where the problem lies. Arthur Link to post Share on other sites More sharing options...
Lady_Ava_Hay Posted October 11, 2011 Share Posted October 11, 2011 If it runs fine without the coupling rods then the issue is the reverse wind up caused by the rods jamming. If I am correct in seeing threads on the temporary crank pins then I think you have an accumulation of problems all related to the rod / pin combo. Link to post Share on other sites More sharing options...
Katier Posted October 11, 2011 Author Share Posted October 11, 2011 Those aren't temporary.. they are the final pins (as supplied).. just not cut to length. Link to post Share on other sites More sharing options...
Lady_Ava_Hay Posted October 11, 2011 Share Posted October 11, 2011 Those aren't temporary.. they are the final pins (as supplied).. just not cut to length. That's a surprise. In engineering terms, running a soft(ish) metal hole on a harder screw thread is a recipe for binding as the threads are attempting to screw the rod into the wheel on one side and away from it on the other. I honestly think that the use of either bushes or replacement smooth pins a la Romford will cure your ills on this chassis. Link to post Share on other sites More sharing options...
Katier Posted October 11, 2011 Author Share Posted October 11, 2011 Thanks - while I suspect I may be able to fix it with the current pins.. Not happy with them anyway so I'll order some Romford pins and have a go with them. Anything I need to know about the Romford pins? BTW as you can tell the current wheels are just a press fit, should I glue them in place with anything ( worried about them working loose) Link to post Share on other sites More sharing options...
craigwelsh Posted October 12, 2011 Share Posted October 12, 2011 You might be able to use bushes from Alan Gibson or Ultrascale on those threads. I think Ultrascale use 14BA but I keep forgetting to check.. I don't know if those Romford supply will be ok on 3mm scale wheels. One thing I'd not picked up on earlier was you said it runs fine being 'pushed' along. Try getting it to roll along on a slight gradient, its normally a better test without any outside interference. Link to post Share on other sites More sharing options...
Katier Posted October 12, 2011 Author Share Posted October 12, 2011 So I would slide the bushes over the threads, then bushes I assume are bolted tight to the wheel while the connecting rod 'floats' on the bush? Pretty sure I have a set of Romford style wheels too for a different kit. So may well have some Romford crank pins - just didn't realise till I did a bit of research following this thread. I believe Romford 4mm wheels are sometimes used in 3mm due to the small range of specific 3mm wheels - wheels aren't as bad as n-gauge ( where the 2mm wheels won't work properly on n-gauge spec track) but still not great. These wheels I think are society finescale wheels. I am a little concerns that the bearing seem very substantial for quite a small loco, would I have been better off with straw hats for the front axle. BTW should I use any lubrication anywhere? Link to post Share on other sites More sharing options...
RMweb Premium DLT Posted October 12, 2011 RMweb Premium Share Posted October 12, 2011 Regarding the gearing, the Slimliner+ is a very nice gearbox, I've just used one myself. I have foud that the swinging portion of the box needs to be locked in position relative to the main part (once you've found its best position of course!) A smear of Araldite in the outside should do it. Looking at the worm, can you move it a bit further onto the motor spindle, closer to the motor? In the position its in it may not be in full mesh with the first gearwheel. Hope this helps, Good luck, Dave. Link to post Share on other sites More sharing options...
RMweb Premium DLT Posted October 12, 2011 RMweb Premium Share Posted October 12, 2011 So I would slide the bushes over the threads, then bushes I assume are bolted tight to the wheel while the connecting rod 'floats' on the bush? Thats right. Can you straighten out the coupling rods and check that the spacing of the holes matches the spacing of the axles? And could the rod be bent in the other direction? Lie it flat on the bench and put a straight edge along it to check that the holes are in line. Cheers, Dave. Link to post Share on other sites More sharing options...
Katier Posted October 12, 2011 Author Share Posted October 12, 2011 Looking at the worm, can you move it a bit further onto the motor spindle, closer to the motor? In the position its in it may not be in full mesh with the first gearwheel. Sadly not.. I've tried!!! There does appear to be 'enough' mesh. I've found my Romford 'bushes' for the other wheelset and think i'm going to try the hybrid approach of the current bolts with Romford bushes. The spacing is correct as far as I can tell.. I'm tending towards issues with poorly restrained connecting rods initially at least. Regarding the slimliner, in this case I 'think' it'll be ok with the 'lid on' as the body is a pretty close fit but I'll bear it in mind Link to post Share on other sites More sharing options...
Katier Posted October 12, 2011 Author Share Posted October 12, 2011 Progress.. of a sort. Installed the Romford nuts I had which certainly make more sense than the bolts I had before. If I connect the rear two axles it works fine, connect the front too it binds.. Assume this means I have a slightly off center hole in one of the connecting rods? Link to post Share on other sites More sharing options...
Arthur Posted October 12, 2011 Share Posted October 12, 2011 Narrowing it down for sure! Two possibilities, one is an error in the front axle quartering. The other a mismatch between axle spacing and coupling rod holes. Have you a vernier caliper or a set of dividers to check with? Also worth checking that the leading axle is at right angles in the frames and that the crankpins are too. Link to post Share on other sites More sharing options...
Katier Posted October 12, 2011 Author Share Posted October 12, 2011 I only have a cheap plastic set of verniers ( came in a cheap jewelry making kit of all things - bought for the pliers) and there does seem to be a slight difference in the front distance... Now I know for sure the crankpins are at right angles ( because they are those bolts so basically self squaring).. Worried it'll be the front axle.. that'll be a PAIN!! Link to post Share on other sites More sharing options...
Katier Posted October 12, 2011 Author Share Posted October 12, 2011 Ok using same set of verniers the front two axles MIGHT be a smidgeon out.. when I mean a smidgeon I mean one side is a touch tighter than the other.. I'm getting we are talking in the thou's for the difference.. if that. Link to post Share on other sites More sharing options...
Arthur Posted October 12, 2011 Share Posted October 12, 2011 How tight a fit are your coupling rods over the crankpin bushes? They need to be a working fit, not too tight, obviously not too loose either! I'm just wondering if they need opening out a little but proceed with caution, too much and they're ruined. Link to post Share on other sites More sharing options...
hollywoodfoundry Posted October 12, 2011 Share Posted October 12, 2011 It may be a trick of the photograph, but the rear axle, or I assume it is the rear axle, in any case the one under the motor, does not appear to be square with the chassis. This would not help in getting the chassis to work with the rods fitted. Link to post Share on other sites More sharing options...
Katier Posted October 12, 2011 Author Share Posted October 12, 2011 YEY success.. Well kinda.. She certainly works now after opening the coupling rod holes a bit.. not convinced there's much power there (or conversely worried there might be too much friction in the system) but she does run. Link to post Share on other sites More sharing options...
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