plastic top hat bearings

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philpill

plastic top hat bearings

Postby philpill » Tue Feb 16, 2016 9:58 am

anyone know supplier of plastic or other non conductive top hat bearings having same dimensions as brass ones used on loco axles seen some on industrial sites ideal but min qty 1000 perhaps stores will stock them !

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Weskie
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Re: plastic top hat bearings

Postby Weskie » Tue Feb 16, 2016 7:19 pm

Try searching for PTFE internal bush, as used in fishing poles.
Andy Westcott

Terry Bendall
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Re: plastic top hat bearings

Postby Terry Bendall » Wed Feb 17, 2016 8:02 am

A possible solution would be to use plastic tubing. Choose a size that has a hole that will fit your axle and then one that will slip over to give the enlarged ring for the end. If the hole is not quite right, opening it out with a drill should be OK since the drill will follow the existing hole. Ideally of course you need nylon or something fairly hard but depending on the application ABS plastic would probably work.

Alternatively find someone with a lathe who can turn some up for you. :)

Terry Bendall

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Andy W
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Re: plastic top hat bearings

Postby Andy W » Wed Feb 17, 2016 8:14 am

The only use for such bearings I can think of is to isolate an axle in split frame - to mount a motor on it. This is probably only advisable on 4 or 5 axled loco as otherwise there would be a significant drop in current collection.
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philpill

Re: plastic top hat bearings

Postby philpill » Wed Feb 17, 2016 8:25 am

i was thinking more for 240 or 042 locos would you have to make up split for the thinner axle the other alternative is exactoscale plastic hornguides with a reduced bore in the exactoscale bearing

dal-t
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Re: plastic top hat bearings

Postby dal-t » Wed Feb 17, 2016 8:34 am

If you haven't already seen it, you might like to look at this link.
David L-T

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Andy W
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Re: plastic top hat bearings

Postby Andy W » Wed Feb 17, 2016 9:48 am

Branchlines also do 2mm split axles. They may have some of the old Kean Maygib plastic hornblocks as well.
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philpill

Re: plastic top hat bearings

Postby philpill » Wed Feb 17, 2016 10:37 am

Hi thanks Andy have ordered from branchlines they have both sizes in stock but you need to make your own insulating washer for the 2mm :D

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Andy W
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Re: plastic top hat bearings

Postby Andy W » Wed Feb 17, 2016 9:30 pm

Oh. That didn't used to be the case. The ink tube from an old biro might do the trick.
Make Worcestershire great again.
Build a wall along the Herefordshire border and make them pay for it.

philpill

Re: plastic top hat bearings

Postby philpill » Wed Feb 17, 2016 10:08 pm

Hi Andy mislead you there they still do washers for 2mm axle but currently havent any but do have the 2mm axle bits thanks for tip re ballpoint pen

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Re: plastic top hat bearings

Postby Terry Bendall » Thu Feb 18, 2016 10:15 pm

Andy W wrote:The only use for such bearings I can think of is to isolate an axle in split frame - to mount a motor on it. This is probably only advisable on 4 or 5 axled loco as otherwise there would be a significant drop in current collection.


Barry Luck has been a user of split axles for many years including three part ones for the drive gear and gearbox. His ideas were written up in MRJs 19 and 20 if you can find copies. Certainly no need for insulated axle bearings.

Terry Bendall

philpill

Re: plastic top hat bearings

Postby philpill » Thu Feb 18, 2016 10:30 pm

Thanks Terry have ordered copies on ebay gave my old copies away when i gave up modelling for 10 years

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Knuckles
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Re: plastic top hat bearings

Postby Knuckles » Fri Feb 19, 2016 8:55 pm

Just slightly slightly off topic by a few compounds, but (always a But in the way! Me in this case) I have a brass kit I am looking forward to 'P4-ing,' but it comes with white metal 1/8th top hat bearings/bushes! I have only ever used brass and I am assuming WM may be a bit soft.

Shall I turn them into scrap scenery and just use brass ones or are they actually any cop? Maybe the softeness could be useful...or maybe not.

?
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Paul Willis
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Re: plastic top hat bearings

Postby Paul Willis » Fri Feb 19, 2016 9:32 pm

Knuckles wrote:Just slightly slightly off topic by a few compounds, but (always a But in the way! Me in this case) I have a brass kit I am looking forward to 'P4-ing,' but it comes with white metal 1/8th top hat bearings/bushes! I have only ever used brass and I am assuming WM may be a bit soft.

Shall I turn them into scrap scenery and just use brass ones or are they actually any cop? Maybe the softeness could be useful...or maybe not.

?


I'd be using brass ones...

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dal-t
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Re: plastic top hat bearings

Postby dal-t » Sat Feb 20, 2016 9:15 am

I thought phosphor bronze was the bearing material - at least Jim McGeown says it is, and I wouldn't be disagreeing with him. But doesn't the 12":1' railway use white metal for (sliding contact) bearings?
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Re: plastic top hat bearings

Postby shipbadger » Sat Feb 20, 2016 6:24 pm

Yes, white metal is used for bearings on 12":1' railways and was standard until roller bearings came along for axles, late 40's-early 50's. If the scrawl on the outside of the locked cabinet is to be believed we have a supply in the cupboards of the ** railway restoration shed. Also used for car crankshaft bearings until around the time of WWII. Lasted around 25-30K miles in a car engine. In both cases the bearing needs to be carefully scraped to fit it's mating component, a job which requires skill and patience. Whilst in theory white metal could be used for model bearing for good quality running it would seem likely that they would be a bit of a faff to set up. All you need are disimilar metals. Steel and brass or steel and phosphor bronze to reduce friction in a bearing.

Some wagon and coach wheels (Steam Era etc) are now provided with brass axles. This is to overcome steel axles being 'grabbed' by magnets, in particular those for uncoupling Kadees. Would anyone like to comment on how these perform with brass bearing cups.

Tony Comber

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Knuckles
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Re: plastic top hat bearings

Postby Knuckles » Sat Feb 20, 2016 9:03 pm

Seeing as white metal is low melting wouldn't they melt on the real railway considering the extra friction, weight and speed? :?
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Guy Rixon
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Re: plastic top hat bearings

Postby Guy Rixon » Sat Feb 20, 2016 10:51 pm

Knuckles wrote:Seeing as white metal is low melting wouldn't they melt on the real railway considering the extra friction, weight and speed? :?

Yes, if the lubrication failed. Hot boxes were a major hazard, particularly with grease axleboxes where the grease ran out as it heated and was lost.

Also, I believe that the reason for the larger (3'6") wheels in passenger stock and NPCS was to reduce the surface speed in the bearings to moderate the friction.

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Knuckles
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Re: plastic top hat bearings

Postby Knuckles » Sun Feb 21, 2016 12:40 am

Fair enough. I have heard of hot axle boxes before but didn't know that was the reason. I guess that is why grease boxes fell out of use.

White metal still seems a strange choice to me for a bearing on a full size loco. :roll:
“He who dares not offend cannot be honest.” Thomas Paine

https://www.sparkshotcustomcreations.com/
Mostly 3D Printed Loco kits etc.

SCC Price list (7/4/22)
https://www.sparkshotcustomcreations.co ... e77d42.pdf

garethashenden
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Re: plastic top hat bearings

Postby garethashenden » Sun Feb 21, 2016 4:06 am

For bearings it's often referred to as "babbitt" rather than white metal. https://en.wikipedia.org/wiki/Babbitt_%28alloy%29

philpill

Re: plastic top hat bearings

Postby philpill » Sun Feb 21, 2016 9:07 am

back to plastic bearings if every member donated 25p to the cause we could purchase 1000 and give them to Jeremy to distribute at will

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Noel
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Re: plastic top hat bearings

Postby Noel » Sun Feb 21, 2016 12:25 pm

Knuckles wrote: I have heard of hot axle boxes before but didn't know that was the reason. I guess that is why grease boxes fell out of use


In south Wales valleys sheep were apparently prone to eating the grease, so that axleboxes had to be refilled if a wagon stood in colliery sidings too long. However, the main reasons for the replacing of grease boxes were that the lubrication was ineffective until the grease warmed up, which took a few miles and a lot of extra effort by the loco, and the lack of adequate means of retaining the grease where it was wanted, once it melted, so that the boxes were much higher maintenance than oil boxes, having to be checked and refilled rather frequently. You can still get hot boxes with oil axleboxes, just far less often, assuming proper maintenance. Roller bearings are even better, but still not 100%.

Knuckles wrote:White metal still seems a strange choice to me for a bearing on a full size loco


Cast steel axleboxes had liners, bronze or gunmetal until quite late, then some were manganese. These liners had whitemetal bearing surfaces. I suspect [but don't know] that this is because most steam locos, until quite late in their history, were built to fairly generous tolerances, in engineering terms. White metal, being relatively much softer, would wear to match the axle, and was relatively easy to replace when required.
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Noel

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steamraiser
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Re: plastic top hat bearings

Postby steamraiser » Sun Feb 21, 2016 8:33 pm

Although off topic, whitemetal is still used as a liner for the driving wheel axleboxes on a steam loco.
The whitemetal used is a harder than that we are used to in modelling circles.

Gordon A

Terry Bendall
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Re: plastic top hat bearings

Postby Terry Bendall » Mon Feb 22, 2016 10:26 am

On the Leighton Buzzard Railway one of the 2 foot gauge steam locos that is undergoing overhaul has just had new white metal liners cast into a bronze housing and these are waiting to be machined. The axles are about 3 inches diameter. Interestingly they are only half bearings on the top of the axle only with a keeper underneath to retail the axle. The same idea is in use on the Simplex diesel locos only the bearings are all phosphor bronze with a similar size of axle.

shipbadger wrote:Some wagon and coach wheels (Steam Era etc) are now provided with brass axles


According to Brian Osbourn of Branchlines the reason why these are used on the Black Beetle wheels is because the suppler was unable to but 2mm steel axles in a sensible quantity.

Terry Bendall


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