Any Question Answered

[nick_bastable]

a few extra views   the b2b is correct and when standing on the level the chassis does not wobble ....

 

 

 

 

 

Nick

[Caley Jim]

 

still wondering if the chassis is twisted?

A simple way to check that is to stand it on a mirror and see if all the reflections are symmetrical. Does it run smoothly if you apply power direct to the frames, or the track?

 

Jim

[Donw]

One problem that might have given those symptons would have been the pick ups reversed at one end so two wheels on the track fine four wheels would have been a short. However this is 2mm and presumably has split axle pick up so no chance of being reversed. Could the problem be a short with the 4 wheels on the track? I am thinking perhaps some sideways twist causing a short with the axles either not square or one pair offset to the other.

It is a strange problem.

Don

[queensquare]

That is a bit of a mystery Nick, particularly as it runs fine on its flanges. As Jim said, check the chassis isn't twisted. How tight is the belt drive? could that be having some impact although again, if it runs on flat PCB you would suspect not.

More weight over the centre and toward the front might help if there's room.

 

It's little help I know but all of us who have built successful chassis have also built a number that just don't want to play ball for some inexplicable reason. The design you have there should work, keep at it.

 

Jerry

[Caley Jim]

What Jerry has said is very true. Often you find the problem is something simple, but obscure and it's only by studying the chassis, and often by chance, that you happen to find it. It's difficult to give advice on this case without actually being able to handle the miscreant. ;-(

 

Jim

[Izzy]

Hi Nick,

 

How much end float is there in the layshaft? Could the play allow the large pulley to move up against the frame spacer and short when the chassis is powered and under load? With one set of wheels ploughing on the sleepers it might produce the kind of load that keeps it away from the spacer, and running on the rims might not give the high tractive effort the treads on track would.

 

Izzy

[Ian Smith]

Hi Nick,

 

How much end float is there in the layshaft? Could the play allow the large pulley to move up against the frame spacer and short when the chassis is powered and under load? With one set of wheels ploughing on the sleepers it might produce the kind of load that keeps it away from the spacer, and running on the rims might not give the high tractive effort the treads on track would.

 

Izzy

 

Nick,

In your original end on photo, it does look like the pulley is slightly offset from the centre line.  The belt looks a lot closer to the right hand frame than it does the left, if there is any fore-aft movement could the belt be catching on the inside of the frame?

 

Ian

 

edit : Although having looked again at the underside view it looks like the pulley/belt is closer to the left hand frame (from the front) i.e. the one at the bottom of the photo.  So is there lateral play/ wobbly pulley at work too?

Edited July 29, 2016 by Ian Smith

[Ian Morgan]

possibly axles not at right angles to the rails?, or front and rear wheels not in line with each other?

[Alex Duckworth]

It looks to me as if the top set (front and back) of wheels are in line with each other fore and aft but the lower set are not, the bottom non-pulley end wheel seems much closer to the frame. May be worth checking BtoBs and flanges in line fore and aft. It might just be misleading camera angles but worth checking all the same.

 

Alex.

[nick_bastable]

people 

 

many thanks for all the helpful comments and suggestions alas none of which work,   I have concluded that chassis Mk3 is the solution Mk2 was close but not near enough Mk3 will use more rigid spacers and careful attention to getting it straight and level, the good thing is that most of mk2 can be reused

 

once again thanks

 

 

Nick 

[Tim V]

Very long wheelbase, does it have any form of compensation?

[nick_bastable]

Very long wheelbase, does it have any form of compensation?

34mm between centres simpson springs fitted 

 

Nick

[Donw]

Do you have an ammeter in your toolkit. That could provide some useful info. Apply the power via the ammeter on the bench (direct to the motor or as near as possible) to give a no load current reading then place on a bit of track fed via the ammeter.  If that shows no current the pick up is failing if the current is much higher but no movement suggests a stall. If the current is a little higher but no movement it could be the belt slipping.

 

Don

[Caley Jim]

Before you start on mk3, it's important to try and identify whether the problem is electrical or mechanical. Don's suggestion will go some considerable way to doing this. I'm a great believer in compensation for locos as it helps to ensure that not only are all wheels contacting the rails, but they are also carrying enough weight to make good contact. Perhaps it might be possible to arrange the axle at the non-drive end to pivot about the worm shaft. This would keep the worm/wormwheel centres constant.

 

Jim

 

Edited to correct predictive spelling, which never seems to predict what you actually wanted!

Edited July 29, 2016 by Caley Jim

[nick_bastable]

Jim perhaps I did not make it clear Mk1 was single worm and just slipped, mk2 is both axles driven by worm/gears 

 

still less than satisfactory I think the belts tension is now  suspect and can not find my  spares  ( I must have put them somewhere safe   )   however the amperage test proved  very little wrong with the motor when it gets juice.   Having watched pannier 1638 stopped part the way up  Tenterden bank yesterday the effort to get the train moving again was immense bringing most staff out to watch the effort so its not only model that suffer poor traction... 

 

Anyway have spent the morning cutting and filing a new set of frames and rereading old Journal articles  regarding chassis building

 

Nick

Edited July 31, 2016 by nick_bastable

[2mmMark]

It looks like you've used the components that Nigel Lawton uses for his MPD18 chassis.  I built one of those to make a powered van to push my Aveling & Porter loco.  Initially, it had similar symptoms to your chassis.

 

One of the worm/wheel (Tenshodo I think) sets meshed perfectly, the other was a bit fussy and I resolved it by shifting the wormwheel slightly off-centre. I think this was because I'd opened out the axle holes after adding some washers to widen the axle bearing surface and the mesh was slightly altered.

 

Mark

[nick_bastable]

It looks like you've used the components that Nigel Lawton uses for his MPD18 chassis.  I built one of those to make a powered van to push my Aveling & Porter loco.  Initially, it had similar symptoms to your chassis.

 

One of the worm/wheel (Tenshodo I think) sets meshed perfectly, the other was a bit fussy and I resolved it by shifting the wormwheel slightly off-centre. I think this was because I'd opened out the axle holes after adding some washers to widen the axle bearing surface and the mesh was slightly altered.

 

Mark

confession time I used the idea after seeing your version although I'm using association gears and muffs

 

Nick

[PeteDavey]

I'm currently embarking on a rather ambitious (and perhaps over complicated) 3 level fictitious layout that will incorporate 2 heli (helix's). I'm using easitrac concrete sleepers and code 40 flat bottom rail for the plain line and currently building the points using the tried and trusted pcb/solder method. I have a couple of questions regarding the track laying on the heli. I'm tempted to try to build the plain line in one continuous length using 10m coils of code 40 rail to avoid unessessary joints in the rail in difficult to reach places, however I fear this may prove impractical with potential damage being caused to the track during the laying process. My question are as follows:

 

1) If I was to build as planned, does easitrac have sufficient 'give' to allow for expansion when laid in a continuous coil with distortion or would I need to allow for expansion gaps?

 

2) If I was to lay the track in 500mm sections would I need to rely on aligning the rails by careful tweaking as is the norm in scenic areas or are functional fish plates available for code 40 flat bottom rail?

 

3) I have already built the layout in peco code 80 but was dissatisfied with the toy train looking track so it was taken to the local recycling centre with no more than a few lessons learnt on gradients, baseboard building etc with no scenery ever being laid. So my final question is this; The harshest gradient I have on the layout is a hidden 1:60 on a 16" radius which the Diesels I plan on running could pull 40 wagons or 12 coaches up without incident. Would this still be the case with 2mm or will I have a problem because the tolerances are finer?

 

Sorry for the long post but wanted to get some opinions before layout number 2 is resigned to the bin.

 

Any help, advice will be gratefully received as always.

 

Pete

[Caley Jim]

... My question are as follows:

 

1) If I was to build as planned, does easitrac have sufficient 'give' to allow for expansion when laid in a continuous coil with distortion or would I need to allow for expansion gaps?

 

2) If I was to lay the track in 500mm sections would I need to rely on aligning the rails by careful tweaking as is the norm in scenic areas or are functional fish plates available for code 40 flat bottom rail?

 

3) I have already built the layout in peco code 80 but was dissatisfied with the toy train looking track so it was taken to the local recycling centre with no more than a few lessons learnt on gradients, baseboard building etc with no scenery ever being laid. So my final question is this; The harshest gradient I have on the layout is a hidden 1:60 on a 16" radius which the Diesels I plan on running could pull 40 wagons or 12 coaches up without incident. Would this still be the case with 2mm or will I have a problem because the tolerances are finer?

I don't have any direct experience of such and arrangement (I doubt many have), but my thoughts would be:

 

1) Unless the temperature in the intended location is fairly constant, I would definitely lay in 500mm (max) lengths, as you suggest, with gaps for expansion.

 

2) Provided that you fix the sleepers around each rail joint firmly down, or better still, stagger the joints in the two rails so that they don't occur at the same sleeper gap, functional fishplates shouldn't be needed.  If you remain to be convinced, they can easily be made by folding a narrow strip of copper or brass shim round the base of the rail.  This is the way I made them for my loose-heel switches on Kirkallanmuir.

 

3) Can't comment on this, but I can't see any reason why 2FS should be different to N in this regard, though I stand to be corrected by those with experience of both.

 

HTH,

 

Jim

[PeteDavey]

Thank you Jim. I'm guessing if the easitrac has a soldered PCB sleeper at each end of a 500mm length, and the soldering done whilst the track is pinned over a template then it would essentially become 'set track' which if carefully laid could have an expansion gap set with feeler gauges and wouldn't need fish plates?

[Graham R]

Thank you Jim. I'm guessing if the easitrac has a soldered PCB sleeper at each end of a 500mm length, and the soldering done whilst the track is pinned over a template then it would essentially become 'set track' which if carefully laid could have an expansion gap set with feeler gauges and wouldn't need fish plates?

 

If it's hidden, and your main concern is to avoid derailments on the outer rail of the curve at the expansion joints, you could simply put a short checkrail on the inside rail at the joint.

Graham

[Donw]

My only thoughts are that 16in radius is quite tight, the rewheeling should cause no problems but some people have improved the looks of diesels by lowering the bodies. This might not be practical with such radii. The tight radius will also cause a fair amount of drag. You mention a 1:60 on the 16inch curve was this on the helix of just a short curve it can make a difference if only part of the train is on the curve. Eg. at 16in rad a quarter circle is about 25 inch long so a train of 12 coaches would only have about half its length on the curve whereas a half circle would have nearly all on the curve and a helix could be a continous curve equivalent to several revolutions. I would not recommend such a tight curve on the helix if you have the room for bigger 

Incidentally you could use the plain code 40 strip which is still advertised in 10metre coils for the helix assuming it will not be scenic. Coupled with PCB sleepers at triple spacing . It should be quite strong enough.  If you do use the FB rail and easitrac I would put a suitable curve into the rail first as if the rail is pulled into shape when laying it will try to straighten and you can end up with a lot of bad joints

Don

[PeteDavey]

Thank you Don, I was thinking of using the easitrac Plastic sleepers with a pcb sleeper between each sprue of 6, with 3 pcb sleepers at the end of each 500mm piece, this would allow plenty of space to solder the excellent check rail idea that Graham has given me, so thank you too Graham. The radius is 16" on the inner track which is down only so I'm hoping the additional friction would be overcome by gravity. I may do a mock up and try it with a finescaled diesel and coaches and see what happens

[Izzy]

Thank you Don, I was thinking of using the easitrac Plastic sleepers with a pcb sleeper between each sprue of 6, with 3 pcb sleepers at the end of each 500mm piece, this would allow plenty of space to solder the excellent check rail idea that Graham has given me, so thank you too Graham. The radius is 16" on the inner track which is down only so I'm hoping the additional friction would be overcome by gravity. I may do a mock up and try it with a finescaled diesel and coaches and see what happens

 

As the 2FS wheel profile is in my experience less forgiving of rail joint differences on tighter curves than the normally used N gauge RP25 one - any slight error leading to derailment (flange riding up over the rail), the fitting of an inner checkrail across each joint seems an excellent idea as does the use of PCB sleepers at regular intervals. Whatever method/glue I have used I have found easitrac to keep lifting sleepers on track with anything other than gentle curves i.e. above 24", so make sure the track is well stuck down at 16".  I have not found any real issues with hauledge capacity around curves above about 18" but below this as the radius reduces there is certainly increased drag which becomes very noticeable once 12" is reached. This is all on the flat, what effect the addition of an incline would have I'm afraid I have no idea.

 

Izzy

[PeteDavey]

Thank you Izzy, I feel some testing is in order! Last couple of silly questions for a while, I promise!

 

1) Is there a diesel which is notoriously difficult on anything but perfect track work which I can convert to 2mm for the benefit of testing?

 

2) Does a association concrete PCB sleeper match the height of easitrac or do I need to use a chair such as the versaline variety soldered in between?

 

Hopefully my next post will be some pictures and results of a test!

 

Pete