Another Mystery Loco?

[Southerner]

I have a 4mm Dean Goods made from a whitemetal kit with a tender mounted KTM open frame motor driving through a stiff wire shaft to a nicely engineered layshaft  worm and gear. The tender chassis baseplate is marked 'Copyright Mallard Models 1973'  the uncertainty in my mind is that all the info on Mallard Models that I can find suggests that they were etched brass construction, this one is all whitemetal including the tender.

I'm struggling to get it to run well, the wire drive shaft runs under the cab floor and tends to vibrate and resonate like a guitar string under load and speed, I may have to consider loco drive yet { (

I'll now attempt to upload a few photos, here goes!

 

[Tim V]

Loco and wheels look K's to me. I would keep the tender motor - a bit of tuning of the wire will see it running fine.

[Southerner]

Loco and wheels look K's to me. I would keep the tender motor - a bit of tuning of the wire will see it running fine.

Is it K's, I wonder why the Mallard Models plate?

 

[Nearholmer]

The wire drive looks to me as if it is driving the loco flywheel at a point away from dead centre. If it is, that’s why it vibrates.

 

If you make sure the wire heads for the centre of the flywheel, and put a little step in it, right at the flywheel face, to reach an off-centre hole, things should be better, but you might have to change it for a stouter shaft with a couple of UJs in it to achieve really smooth operation. Even with things aligned dead centre, wire is likely to try to ‘belly’, spinning like a skipping-rope.

Edited October 28, 2017 by Nearholmer

[Southerner]

The wire drive looks to me as if it is driving the loco flywheel at a point away from dead centre. If it is, that’s why it vibrates.

 

If you make sure the wire heads for the centre of the flywheel, and put a little step in it, right at the flywheel face, to reach an off-centre hole, things should be better, but you might have to change it for a stouter shaft with a couple of UJs in it to achieve really smooth operation. Even with things aligned dead centre, wire is likely to try to ‘belly’, spinning like a skipping-rope.

Thanks, you've described the problem well, any idea on where I could obtain suitable drive components?

[Nearholmer]

If you’ve got access to a lathe, which you’d need to bore holes in the flywheels, you could DIY, in that UJs aren’t hard to make. Just remember to fit the two UJs ninety degrees out of phase with one another.

 

I know that a US makers sells tiny delrin UJs, but I’m afraid I can’t remember who, and I don’t know much about UK suppliers of such bits. You don’t live near a RC model car shop do you?!they tend to stock such things.

Edited October 28, 2017 by Nearholmer

[bertiedog]

There is good news and bad, the universals are not needed, use silicon tube, with two joints.

 

From what I can see the front shaft through the flywheel will need extending by replacing the shaft, which should be 3/32

 

This is sold in ebay or any model engineering shop, get silver steel.

 

The same applies to the motor end but read on.

 

The shaft lengths are cut about an inch short of each other, and the gap filled with two pieces of silicon tube, with a short piece of silver steel between them. You can add two 2.mm balls in each joint, the middle shaft should be over the tender pivot.

The tubing should be thin wall 1.00mm to 1.5mm max

 

Now,comes the problem, that is the motor shaft will not be long enough to extend to the loco tender gap, and the silicon joint..

So in some way the shaft needs extension, maybe using the flywheel as a sleeve. This is solvable, but without the loco on the bench I can't be certain what way is best.

 

Please ask for any other advice, the design is sound and if in order should run very well indeed, There are lots of other solutions as well, some would need access to a lathe..

Stephen

[bertiedog]

If you’ve got access to a lathe, which you’d need to bore holes in the flywheels, you could DIY, in that UJs aren’t hard to make. Just remember to fit the two UJs ninety degrees out of phase with one another.

 

I know that a US makers sells tiny delrin UJs, but I’m afraid I can’t remember who, and I don’t know much about UK suppliers of such bits. You don’t live near a RC model car shop do you?!they tend to stock such things.

Ultrascale and Markits do UJs..... but the silicon tube works without a lathe.

[Nearholmer]

Blooming good idea.

[bertiedog]

Ebay has 2mm internal bore tube for £1.10 for half metre,

Stephen

[bertiedog]

Dependant on the parts I would suggest taking the fly wheel off the motor shaft and investigate shortening it a bit so that the flywheel acts as  the sleeve for the shaft extension....use proper long set Araldite epoxy to reassemble

Stephen

[Southerner]

With thanks to Tim V, Nearholmer and bertiedog for your inputs and ideas.

The 'Mystery' loco original posting is now solved; pretty obvious really. As already suggested it's a (much modified) K's, the Mallard Models plate is a red herring, it's a scrap piece of a different kit etch reused as a motor mount!

 

As for the running qualities, the main problem is revealed on fitting the loco body to the chassis, the drive shaft runs between the underneath of the cab floor and the chassis, the clearance between  is tight, as the shaft rotates it just touches the cab floor which acts as a sounding board. The cab is nicely detailed and I'm not keen to raise the floor, I may be able to also tweak the wire shaft enough to help matters but it's doubtful.

So I think it's a nicely thought out and detailed kit conversion that was not completely carried through to iron out the snags, a major example being the motor flywheel which was so far out of round and balance that it had the effect of a pager buzzer, easily cured though with a coarse file gently held on  it whilst running!  { )

Oh the joys of other peoples unfinished projects, nice one though it is!

Edited October 29, 2017 by Southerner

[bertiedog]

As the wire drive goes under the footplate I would persist with it, perhaps a sleeve of 1mm heat shrink plastic insulation would just stiffen it a bit. With all the flywheels it should run well, and even coast a bit, but before anything else make sure the chassis is checked over for tight spots, cleaned up, etc.

The layout is a clone of Guy Williams type drive.

Stephen

[Southerner]

As the wire drive goes under the footplate I would persist with it, perhaps a sleeve of 1mm heat shrink plastic insulation would just stiffen it a bit. With all the flywheels it should run well, and even coast a bit, but before anything else make sure the chassis is checked over for tight spots, cleaned up, etc.

The layout is a clone of Guy Williams type drive.

Stephen

Thanks Stephen, I won't give up on it yet and will get there I'm sure, all of your suggestions have been most helpful.

Doug