Split frame chassis

[bertiedog]

I bought 3 Mainline split chassis models when they first came out. I did not use them but packed them away until I had a suitable layout. A few years ago I got them out and tried to run them.

One would not run at all - the chassis sides were warped and brittle, when I dismantled it, it virtually fell apart - definitely not curable.

The second one did run, very badly - all the wheels were wobbly due to the plastic muffs all being cracked, again the chassis had deteriorated, not as badly as the first, but not worth persevering with.

The third one was relatively OK and has been DCC chipped and is still running.

 

Keith

 

Well you got the bad example!!! The warping and diecast disease was another Chinese issue that still haunts certain well known examples, and the motors were delivered with bearings that were so oversized that the shaft could move sideways by 30 thou or more, yet intermediate gears between the motor and axles were jammed on tight!! the pitch circle of the gears on the axle did not match the intermediate gears pitch circle!!, and the gears were straight tooth profile not involute form, all basic engineering mistakes....add the plastic sleeves not fiiting, and the cast stub axles and the locos barely ran.except at higher speed, where sheer effort overcame the problems, with a lot of noise!!

 

Stephen.

[melmerby]

Well you got the bad example!!! The warping and diecast disease was another Chinese issue that still haunts certain well known examples, and the motors were delivered with bearings that were so oversized that the shaft could move sideways by 30 thou or more, yet intermediate gears between the motor and axles were jammed on tight!! the pitch circle of the gears on the axle did not match the intermediate gears pitch circle!!, and the gears were straight tooth profile not involute form, all basic engineering mistakes....add the plastic sleeves not fiiting, and the cast stub axles and the locos barely ran.except at higher speed, where sheer effort overcame the problems, with a lot of noise!!

 

Stephen.

The first was a 57XX, it now has a Comet chassis

The second was a 43XX it will have a Comet chassis (still in it's packing awaiting construction!)

The third was a Manor, still limping along.

Actually the retailer I bought them from new warned me at the time that the production standards were somewhat variable.

 

Keith

[LTMET]

I don't have a lathe, but I have split axles on an Alan Gibson 4mm J15 and its tender just by using the piercing saw method.

The axle is held in a vice and a cut made in the shape of an "L" where the foot of the L is half way through the axle (ie running along the length of the axle). The gap is filled with araldite and left to cure.

The axle is then turned over and a cut made from the other side and again filled with araldite.

The area of the cut is then smeared with araldite, cotton thread is wound around it and then a brass sleeve is slid over the araldite impregnated cotton to add strength.

An old method described in Railway Modeller (September 1986), but it works. Frames separated by copperclad spacers and a narrow gearbox complete the job.

[John_Hughes]

I don't have a lathe, but I have split axles on an Alan Gibson 4mm J15 and its tender just by using the piercing saw method.

The axle is held in a vice and a cut made in the shape of an "L" where the foot of the L is half way through the axle (ie running along the length of the axle). The gap is filled with araldite and left to cure.

The axle is then turned over and a cut made from the other side and again filled with araldite.

The area of the cut is then smeared with araldite, cotton thread is wound around it and then a brass sleeve is slid over the araldite impregnated cotton to add strength.

An old method described in Railway Modeller (September 1986), but it works. Frames separated by copperclad spacers and a narrow gearbox complete the job.

 

I think the idea goes back a lot further than that - Don Boreham mentioned it in his Narrow Gauge Modelling back in the 60s if I remember correctly.

 

Not tried it yet myself, but I might one day...

[Torper]

Bill Bedford used to produce kits for the simplest and best split axles I've ever assembled. Basically, they merely comprised a length of 1/8 inch steel tubing with quite a large internal diameter, and a narrower hard steel rod. You'd first cut the tube to the length required for your axle and then wind cotton thread round the hard steel rod, coat it with araldite, and then push the sticky rod into the tube. Result was an external steel axle insulated from the internal hard steel core. When the aradite had cured, you could cut gaps round the axle tube as and where you wanted them. This left the axle in suitably insulated sections, while its integrity was preserved by the internal hard steel core. Foolproof and easy. Unfortunately Bill no longer produces this "kit", and in spite of much trying I have been totally unable to locate suitable 1/8 inch steel tube so that I could make more. Brass tube is readily available in 1/8 inch, but I understand that a brass axle in brass bearings is not a good thing. If anyone knows of a source of 1/8inch steel tube with a fairly large internal diameter I would be eternally grateful!

 

DT

[bertiedog]

Not much thinwall1/8thmild steel is made, you may find stainless steel from Model engineers suppliers like Maxi track.

 

A point on all the ideas that slit axles then fill, then slit and fill, these rely on the strength of the epoxy, and Araldite and other consumer brands are not the same as they used to be. No five minute or quick set of any type are suitable, they have built in flexibility, and the joints fail.

 

It requires, (whatever brand), the original long set type, these go very hard, especially if warmed up in the curing period. Also Talc powder can be mixed into the resin to "fill" the epoxy, making it even more stable when set.

 

Don't forget insulating sleeves do not have to be made on a lathe, simply drill a block of plastic with 1/8th driil, and push the axle stubs in, making sure they don't touch, then put the stub end in an electric drill and sand the outside smooth, the accuracy comes from the hole, not the outside.

 

Stephen.

[Buckjumper]

A point on all the ideas that slit axles then fill, then slit and fill, these rely on the strength of the epoxy, and Araldite and other consumer brands are not the same as they used to be. No five minute or quick set of any type are suitable, they have built in flexibility, and the joints fail.

 

It requires, (whatever brand), the original long set type, these go very hard, especially if warmed up in the curing period. Also Talc powder can be mixed into the resin to "fill" the epoxy, making it even more stable when set.

 

 

Agreed. I, and I know many other 7mm modellers, use this method, but always use the blue/white tubes of Araldite which is the 24 hour stuff. I once inadvertently used the 5 minute set stuff in red/white tubes and after 24 hours set it to work which very soon resulted in an interesting, but useless, bowed axle.

 

I use an offcut of plasticard or brass fret to force the Araldite into the slit until is oozes out the other side before cleaning up, and then leave it on a warm radiator for 24 hours to cure. Thanks for the tip in using talc to impart further stability, I'll give that a try next time.

 

Here is a nicely described variant of this method.

[Torper]

Not much thinwall1/8thmild steel is made,

Unfortunately, that's what I've found duirng my quite extensive research. However, thanks to the help of a member of this group, I've found somewhere that makes suitably sized stainless steel tubing. My only anxiety about that is its electrical conductivity, but hopefully I'll find out about that fairly shortly.

 

It seems quite strange that in this day and age we haven't moved to a metric measurement for our 4mm axles, at least where it comes to kit building. However, I suppose that would mean a prohibitively large and expensive retooling exercise for our wheel manufacturers

 

DT

[ozzyo]

It seems quite strange that in this day and age we haven't moved to a metric measurement for our 4mm axles, at least where it comes to kit building. However, I suppose that would mean a prohibitively large and expensive retooling exercise for our wheel manufacturers

 

DT

 

Not to mention all the people that build kits. Long may the imperial size be there.

 

OzzyO.

[bertiedog]

Unfortunately, that's what I've found duirng my quite extensive research. However, thanks to the help of a member of this group, I've found somewhere that makes suitably sized stainless steel tubing. My only anxiety about that is its electrical conductivity, but hopefully I'll find out about that fairly shortly.

 

It seems quite strange that in this day and age we haven't moved to a metric measurement for our 4mm axles, at least where it comes to kit building. However, I suppose that would mean a prohibitively large and expensive retooling exercise for our wheel manufacturers

 

DT

 

Electrical conductivity is excellent with stainless steel, the only issue as axles is that it has a naturally "rough surface", due to the chrome content, this can wear brass bearings faster than mild steel axles, the cure is to polish the axles with fine emery paper, at least 2000 grit to finish, and then polish with brasso. this removes any surface abrasion, and the bearings last as well or better than with mild steel. Fine emery is made to at least 5000, paint finishers use it, and fine finishing compounds are also made, silver polishes, and fine rubbing compound, all will give a good polish.

 

Stephen.

[billbedford]

Electrical conductivity is excellent with stainless steel, the only issue as axles is that it has a naturally "rough surface", due to the chrome content, this can wear brass bearings faster than mild steel axles,

 

Stainless steel tup is hard drawn and has a surface finish which not notably different to the mild steel axles we are used to. Some grades can be suppled polished.

[Torper]

Thanks Stephen, very helpful (as usual!). I'm still waiting to see if the company concerned will supply me with the small quantities I require - here's hoping!

 

DT

[bertiedog]

Just to clarify, Stainless having a rougher surface is all relative, you will not see it or feel it, it is given away by the extra wear in brass and bronze bearings it causes.

 

At work we made BS test instruments in stainless steel, ( various grades, usually capable of Vacuum Hardening), to specific surface finishes, as they had to be used to test items to BS by comparison. This gave a lot of experience into finishes on steel. Some grades of Stainless are quite abrasive compared with mild steel, the items made were test needles and surface friction was tested, as all parameters had to be known to be able for the items to be used as standards.

 

Stainless that has been drawn into a tube will be surface hardened due to the process and it may pay to heat treat it by heating to red heat and allowing to cool. This should remove the hardness, and allow easier polishing to a good mirror finish.

 

I don't think much easy to obtain polished stock is available, most is used in food and aerospace industrial production. It is used by Model engineers for stainless steel superheater elements, but usually larger than 1/8th.

 

If you using ball races as bearings there is no need to do anything, the ballraces take all the wear, and will work fine with split frame, the chances of the oil in them insulating the race in the real world are near zero.

 

It is also worth polishing mild steel axles as well, a good mirror finish can be obtained, and wear on brass bearings minimised.

 

Stephen.

[bertiedog]

There may be a solution to buying in 1/8th tube, use 3.3mm (cheap and easy to find) and ream out the wheels and gear to 3.3mm (1/8th is 3.175mm), however this really needs a lathe to do it, and you may as well drill out mid steel 1/8th rod. However the tube is stainless and cheap.

 

It would be possible to make the whole tube to insulated form, (over length) for handling, and then reduce to 1/8th, by putting the blank axle in a power drill and using courser abrasive paper to get down to 1/8th, then polish to mirror finish.

 

In a lathe the 3.3mm semi finished could be skimmed down to 1/8th in one pass rough, one pass fine, then polish, the turning should be between centres, the central hole should be faced off accurately before putting the tube between centres

 

Stephen.

[Guest Natalie Graham]

Eileen's Emporium: 3.2mm OD Stainless tube

[billbedford]

1/8 inch stainless steel tube is available in metre lengths in 12 different wall thicknesses. What is uncertain, at the moment, is the minimum order value.

[bertiedog]

The 3.2mm should work all right "as is", as the polishing will remove a bit, and the ends could be sanded to a decent push fit in Gibson wheels, and tapering lead 3.2mm reamer would take the 3..175mm hole on the gear accurately to 3.2 to fit the gear snugly on the driven axle.

 

To do the ends glue fine emery 400 to hardwood strip to keep it flat, put in power drill, and simply run the emery board on the end area, at a taper, til the end just enters the hole, then polish the end area with fine 1000 grit, and it should push home, with a spider etching or home spider to get the power from the rim.

 

Again with the 3.2mm a spider could be drilled at 3.175 in the centre, and it will now be near force fit on the 3.2mm axle.

 

So 3.2mm actually has advantages over an exact 1/8, but it does need a 3.2 reamer with a taper lead to alter existing bearings and the gear centre.

 

So often it is small quantity orders that stymie getting hold of exact materials, but if Eileen's (or others), stock this metric size then use it.

 

For the centre, may I suggest using 1.5 to 2mm steel, with heat shrink plastic sleeve fitted over it, and then slid into place with a coating of long set epoxy, let it set hard then saw the centre slit gap, or at one end, it does not need to stop at the heat shrink, but just make sure that no swarf is left in the slot, and then fill with epoxy. let it set hard, and then sand down any excess epoxy, result a sound straight axle, with reliable heat shrink insulation around the inner core.

 

Cut to length and polish the ends with 400 grit, and then 1000, after painting the insulation should be all but invisible..

 

Stephen..

[bertiedog]

With the heat shrink insulation, I think it will pay to put epoxy on the inner shaft before heating it to shrink, it will ensure it will never shift, also sand the outside of the heat shrink before coating and pushing into the 3.175 or 3.2mm tube. It al ensures a really sound epoxy coating, again only use long set top grade epoxy. I find the black heat shrink works best for this sort of job.

I have not used it for split axles, I but have made custom electrical plugs and sockets with these materials, using exactly these materials and methods, and can see no reason it should not work perfectly.

 

Also, if you use 2mm steel for the inner and adding the heat shrink gives a size too large to go in the tube, then simply chuck in drill and sand down til it fits, with a touch of space for the glue.

Picture gives outline, no complex cutting, no loss of strength, and remains dead straight.

Stephen.

[Guest Natalie Graham]

Is a possible difference of less than .001" going to be significant in terms of needing sanding, polishing, reaming or whatever? I am thinking that unless one can work to very exacting tolerances then it is likely that such operations may introduce a discrepancy greater than that which already exists. After all, 1/8", to one decimal place in mm, as the tube sizes are quoted, is 3.2mm.

 

Another thought regarding split axles but only applicable to P4 is that Exactoscale wheels are designed with a three piece axle consisting of two plastic stub axles and a metal sleeve. As designed the sleeve is supposed to contact the metal inserts in the wheels which will be running in the bearings. I was wondering if the sleeves could be reduced in length and an insulating washer placed between the ends of the sleeves and the wheel inserts or if this would upset some significant feature of the design. The wheel rims would still need connecting electrically to the inserts. Alternatively would those axles work with other makes of wheels?

 

I know a couple of people in the 3mm Society tried conductive paint to make plastic wheels work for split frames. It didn't work on it's own but turned out to be a good foundation for electro-plating with copper which did.

[bertiedog]

The .001 difference might make pushing a Gibson wheel on a bit tight, but it would not work into a brass reamed quality accurate gearwheel, so if it does go through the gear, then you have been supplied with an over sized gear! I very much doubt the Gibson plastic wheel centre would break, but the axle end should have a small taper anyway, it is needed to guide the steel axle through the hole in the plastic..

 

Sanding round tubes and steel rod to reduce diameter works, and work accurately enough to satisfy Swiss watchmakers!! They do it "open", held in a chuck, and also in a chuck, with the far end in a wooden groove board, held against the rotating round shaft, and then apply a hand held wood backed fine abrasive strip, The board stabilises the shaft and concentricity is astonishing, you can work to microns accuracy. It is used to polish in tapers on the end of shafts, needs a bit of practice, but works superbly. Some hand processes like this are forgotten, they were accurate and still are.

 

Stephen.

[bertiedog]

The spider mentioned may be new to some, it allows a no solder way to get the power from the rim to the axle, using two or three legs. It is made from phosphor bronze sheet 3 to 5 thou or so. This can be snipped to shape with scissors, the centres are filed round, and the the centre hole drilled just under sized for the axle, and then opened with a taper broach till it almost goes on the axle,,..... with the chamfered end you can just push it on to the axle, and then tweak the legs outwards, so that when the wheel pushes on it makes contact with the rim,

It needs no soldering at all, three or more legs are best on drivers, and two on tender wheels. The legs must be in line with the spokes and no wide, It occupies on about 5 thou per side, and should fit behind flat backed wheels on standard P4 frames. If the frames are tight, then the frame spacers may need reducing a bit before soldering up, so test this aspect with the etchings for the frames checked out as to the max width.

 

 

Using 145degree solder, and a very hot iron,it is possible to solder the tips to the rims, but frankly it is difficult to judge the timing before the plastic melts, so best left relying on the pressure contact. The forced on centre does not need soldering. One addition before final finishing of the model before use is to gently slide a scalpel blade dipped in Vaseline (BPC), under the tip at the wheel rim, leaving a tiny bit under the contact, this keeps air away and maintains the contact. (Use nothing else but Vaseline).

 

I believe some commercial spiders in etched phosphor bronze have been made in the past, just make sure the legs match the spokes to hid the spider. The commercial ones are half etched with petals in the axle hole that bend back to contact the axle as it is pushed home.

 

Stephen.

[Torper]

Picture gives outline, no complex cutting, no loss of strength, and remains dead straight.

Which is why it is both the easiest and best way of making split axles! The other advantage, of course, is that you're not limited as to where you make your insulation breaks in the axle - it's easy, for example, to make two, one each side of the gears.

 

Incidentally, the company that I'm hoping will send me the 1/8" tube also supplies 2mm tube with an internal diameter of 1.5 mm. I've asked for a length of that as well to see if it would be suitable for split axle tender and bogie wheels.

 

DT

[bertiedog]

Another thought regarding split axles but only applicable to P4 is that Exactoscale wheels are designed with a three piece axle consisting of two plastic stub axles and a metal sleeve. As designed the sleeve is supposed to contact the metal inserts in the wheels which will be running in the bearings. I was wondering if the sleeves could be reduced in length and an insulating washer placed between the ends of the sleeves and the wheel inserts or if this would upset some significant feature of the design. The wheel rims would still need connecting electrically to the inserts. Alternatively would those axles work with other makes of wheels?

 

I know a couple of people in the 3mm Society tried conductive paint to make plastic wheels work for split frames. It didn't work on it's own but turned out to be a good foundation for electro-plating with copper which did.

I had not looked that closely at the Exactoscale apart from a small drawing, but I had assumed the whole point of the way they do it was to give split axle operation. I will try to find a fuller drawing, but all the work of the sleeves and plastic parts seems a waste if it is for ordinary pickups.

 

Do not trust silver or electro conductive paints(years of experience with them in industry!),, they simply are too prone to damage, even coated with epoxy paint. Also in coats no wider than a spoke they may not take much current and burn out.

 

Yes, plating. will work, but there are far easier ways, you could plated all the plastic far easier than just the conductive paint. A plate of copper, then nickel would be best, temporary conductive dipped paints are used to make the whole surface plated. To be reliable the plated spokes would need a wire soldered on to the steel rim,and then to the spoke, but there is less risk to the plastic as it is contained in the metal plating. Alternatively after the initial plating, a small band of conductive paint is added all round the gap, and a second plate done, which will cover and bridge the gap perfectly,

 

A fully plated wheel would make contact with the axle, if the hole is reamed to a lose fit with out the plate, once plated it should then fit the axle. But all of this is complex and would need experiment,and I deeply feel too complex to bother with.

 

Stephen.

[Guest Natalie Graham]

Like I said, they found the conductive paint didn't work but I do know that a couple of people did find it worked well as a basis for plating and successfully converted wheels that way. It was written up in the 3mm Socierty magazine at the time. I never tried it myself, finding it easier to solder a wire from a hole drilled at the edge of the tyre to a hole drilled in the axle and then melt the wire into the back of a spoke with a soldering iron. I've switched to 2mm FS now so modifying wheels for split axles isn't an issue.

 

 

Here is the information on the Exactoscale axles.

[bertiedog]

To make sure the heat shrink will grip the 2mm centre, I have just added some to a 2mm shaft, with a Loctite fast set pro epoxy(to save time), and the heat shrink is quite immovable, I had wondered if after it is set the centre could slide out, but I put it in th lathe and with full tailstock pressure nothing shifts till an enormous push is applied. ,I would firmly assert that the outer tube would be as firmly held, making the heat shrink a very good option, mind you the way it was done in the 1960's was newspaper wound around the inner axle, soaked in epoxy resin, worked just as well!!!!

It's just the heat shrink is so satisfyingly neat!!

 

Stephen