Rigid Chassis Locos?

davebradwell
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Re: Rigid Chassis Locos?

Postby davebradwell » Tue Mar 24, 2020 5:18 pm

So there's folk out there using Romford wheels on P4 axles are there? Is it me as if they're RP25 wheels I can't see how they fit the track at 17.7 b-b. BRMSB will just but they won't go far. What sort of standard is this anyway? It's not going to do much for any outside cylinders, either.

DaveB

Philip Hall
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Re: Rigid Chassis Locos?

Postby Philip Hall » Tue Mar 24, 2020 6:03 pm

Hi Tim,

My skimming off the back of the flanges in EM was in response to an EM customer who required an increased b-b beyond that which results from using the standard EM Markits axle. That axle usually gives a b-b of 16.45mm which is wrong for any standard in EM, and my customer uses (mostly) AG, Sharman and Ultrascale wheels which generally work better at 16.65 - 16.7 mm. My solution was to turn 0.1mm off the back of each tyre which gives a more ‘Ultrascale like’ flange and also increases the b-b. Another solution for that would be to keep the profile as it is and use the little washers 247 Developments sell to increase the b-b. With this I am not touching the tyre surface, merely reducing the back of the flange and then rounding it off with a file. The concentricity of the wheel is therefore not affected. This saves having to mount the wheel in a collet, which I don't normally use, because they are not obtainable for my lathe and I have to make dedicated ones for the occasional job.

Now, if the wheels were to be used for P4, the profile would have to be altered as well, in my case by eye which might upset the Scalefour Thought Police. I don’t have, nor would be able to use on my Unimat SL, a form tool because the Unimat SL is not man enough to use one. I also cannot easily do taper turning to cover the 1:20 coning. All I could do would be to reduce the thickness of the flange (as above) and its depth without touching the tyre surface, just gently (maybe, with a fine file) correcting the root radius, if necessary, where the flange meets the tyre surface. There is a P4 Markits axle, mentioned in previous posts, but I have not seen one of these and don’t know what b-b results from using a standard wheel as a starting point. If the b-b on those were to give (say) 17.5mm or thereabouts, there might be room to turn a bit off the back of the flange, as I have done in EM, which makes it (approx) P4 thickness, and to take a bit off the depth. Then once the correct b-b is sorted out, you would be able to see whether the resultant width of the wheel is acceptable for a particular prototype, or indeed whether the profile is acceptable.

Now your query about split axles. Sawing the axle in half and gluing it back together would have to be done with great care, so that the square ends align with each other, otherwise one of the principle reasons for using these wheels, self quartering, would be lost. Also I couldn’t be bothered to do that, not least because I can’t be bothered with split axles anyway!

The only other way (for me) would be to mount the wheel on an axle and then in a collet (see note above re my lathe) and turn the tyre and flange down to approx P4 but forming a parallel tread with very little root radius. This was promulgated in the Ward-Platt article in Scalefour News 206 and does work; I’ve done this to a couple of sets of old Jackson wagon wheels for a bit of fun and they run a treat. But once again, don’t tell the Thought Police...

The final thing is that what we have works so well that apart from a bit of fun, I can’t see the point. Maybe there is time these days to experiment a bit with all this but It does take such a long time and I want to get through my own Shelf/Stack/Large Sideboard of Shame!

Philip
Last edited by Philip Hall on Tue Mar 24, 2020 7:24 pm, edited 5 times in total.

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Horsetan
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Re: Rigid Chassis Locos?

Postby Horsetan » Tue Mar 24, 2020 6:16 pm

Philip Hall wrote:.... if the flange thickness was to come down a bit more, as it would do for P4, the tyre would be about 2.2mm wide, which is not excessive...


As an aside, HO-finescalers sometimes use 2.2mm-wide wheels (available from Weinert, from example) under the label "RP25-fine"
That would be an ecumenical matter.

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Le Corbusier
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Re: Rigid Chassis Locos?

Postby Le Corbusier » Tue Mar 24, 2020 7:07 pm

Philip Hall wrote:The final thing is that what we have works so well that apart from a bit of fun, I can’t see the point. Maybe there is time these days to experiment a bit with all this but It does take such a long time and I want to get through my own Shelf/Stack/Large Sideboard of Shame!

Philip


Philip,

Thats all very interesting ... thanks for going in to such detail.

From my standpoint its simply a thought exercise and its been interesting reading your comments. Gibson wheels are within my price bracket and to date I have been satisfied with results ... though when cashflow finally allows me to splash out on a lathe I might have a play with some of your 'trueing' techniques.

I knew some had had success running EM wheels on P4 track by I thing thinning the flange .... but I couldn't see how this might be done with the Romford system.

Tim
Tim Lee

PhilipT
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Re: Rigid Chassis Locos?

Postby PhilipT » Tue Mar 24, 2020 7:21 pm

Philip speaks of correcting the root radius which is certainly larger than desirable. About 10 years ago I tried to fathom why Markits wheels run satisfactorily on EM track whereas the late Joe Brooksmith said they shouldn't. I sectioned a rim and found that the radius was about 0.68mm, not the 0.87mm figure from a metricated RP25-110. So the Markits wheel isn't as coarse as might be thought although it would still need attention for P4.

davebradwell
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Re: Rigid Chassis Locos?

Postby davebradwell » Tue Mar 24, 2020 8:16 pm

There can't be anything wrong with your simplified wheel profile, Philip, as the profile called for in the P4 spec is just one of many in use on the railways and tramways. We had a thread a while ago which started with a report on a class 37 derailing and its wheel profile was essentially 2 straight lines with a radius between at the flange root rather than our complex convex flange. Last time I skimmed some wheels I used this successfully just setting the tool at the required 62 deg flange angle and taking a cut. I never do coning - it makes measurement of diameter difficult and someone showed that the angle was inadequate anyway. A very long time ago in my passenger hauling live steam days parallel treads were normal. I doubt if a form tool will work in a small lathe due to the width of cut so it will tend to chatter.

DaveB

Philip Hall
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Re: Rigid Chassis Locos?

Postby Philip Hall » Wed Mar 25, 2020 12:03 am

Thanks Dave,

A friend has just sent me some old Jackson 14mm wheels to reduce to 13 mm for a special vehicle. Although it’s 00, I shall try your 62° angle suggestion, and I was going to do a parallel tread anyway. It’s good to know I’m not alone in occasionally not having any coning!

Philip

Philip

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Jol Wilkinson
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Re: Rigid Chassis Locos?

Postby Jol Wilkinson » Thu Mar 26, 2020 7:44 am

I consider the Markits P4 axles are a poisson rouge. I know that some people use them to build and test chassis with Markits wheels before finally committing to fitting AGW, Ultrascale or other "push on" wheels.

Where tolerances are tight (valve gear, splashers, etc.) then it is bad enough getting clearance with AGW, etc. wheels without going down the route of using wider wheels or having to thin down wheels and tyres that aren't ideal for that.

We would benefit from a narrower tyre profile wheel, which is what I believe the more recent Exactoscale products provided (although the C&W wheels, although I don't know if these are regularly available). Sadly the range didn't provide anything that suited the locos I model, were expensive/rather complex and have gone off the market anyway.

davebradwell
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Re: Rigid Chassis Locos?

Postby davebradwell » Thu Mar 26, 2020 11:16 am

I should add to my basic information on a class 37 wheel profile the fundamental need for a radius at the flange tip, appropriate radius where flange meets tread and chamfer on outside edge of tyre, this latter being essential when passing trailing points. If the blade is lower than the stock rail, a sharp ended wheel can be trapped with reducing gauge until something jumps. This has explained the occasional mystery derailment.

The wheels of this new loco were skimmed because it was splitting points which had been trouble-free for years. It effected a complete cure.

Wouldn't it be a nice touch to use this profile on a class 37? Another unexplored aspect of Finescale.

DaveB

Enigma
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Re: Rigid Chassis Locos?

Postby Enigma » Thu Mar 26, 2020 1:49 pm

I once converted a Lima 08 simply by pushing the wheels out on the axles and skimming the back of the wheel so that the depth of the flange approximated the one on a P4 wheel, A wipe with a file on the edge of the flange as it was spinning in the lathe - and they ran fine. However, the mechanical abomination that was a Lima chassis meant that it didn't actually run very well but not because of the wheel profile.

davebradwell
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Re: Rigid Chassis Locos?

Postby davebradwell » Thu Mar 26, 2020 8:22 pm

Lima chassis might have been a mechanical abomination but my memory of them from a very long time ago was that they would pick-up power and start more reliably than anything else available at the time. There was method in their madness somewhere.

DaveB

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Horsetan
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Re: Rigid Chassis Locos?

Postby Horsetan » Thu Mar 26, 2020 9:30 pm

davebradwell wrote:Lima chassis might have been a mechanical abomination but my memory of them from a very long time ago was that they would pick-up power and start more reliably than anything else available at the time. There was method in their madness somewhere....


They did seem to have a fair few cable runs inside. I seem to remember a few people achieved decent results with their diesels once they were double-motored.
That would be an ecumenical matter.

Enigma
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Re: Rigid Chassis Locos?

Postby Enigma » Fri Mar 27, 2020 12:47 pm

Horsetan wrote:
davebradwell wrote:Lima chassis might have been a mechanical abomination but my memory of them from a very long time ago was that they would pick-up power and start more reliably than anything else available at the time. There was method in their madness somewhere....


They did seem to have a fair few cable runs inside. I seem to remember a few people achieved decent results with their diesels once they were double-motored.


I got good results from the bogie diesels by turning down the original brass wheels, fitting AG coach wheel tyres and turning away the excess brass from the rear. The motors need a bit of running in and my Cl 37 still runs well.

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Steve Carter
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Re: Rigid Chassis Locos?

Postby Steve Carter » Fri Apr 10, 2020 2:51 pm

barrowroad wrote:I have just converted a Bachmann 4MT tank for a member of our group. They all run well. If you want any advice please ask.
Robin


OK Robin, I’ll bite as I have a Bachmann STD. 4 Tank to do.

I’ve read Tim Shackleton articles in MRJ but and I’ve been waiting to see if the Brassmasters Easichas, that has been in development for a few years now, materialised.

I’ve seen Mike Ainsworth’s converted engine and it seems reasonably straight forward or am I kidding myself?

How did you do yours please?

Thanks in advance.

Take care and stay safe.

Steve
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barrowroad
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Re: Rigid Chassis Locos?

Postby barrowroad » Fri Apr 10, 2020 5:44 pm

Steve, My method for converting Bachmann locos uses Alan Gibson wheels and Markits stainless steel crankpins which I have obtained from Roxey Mouldings reference 4MA100 and 4MA103. The latter is quite expensive and as the crank itself is rather overscale I decided to discard it and just use the crankpin - more on this later. This is a great shame as it looks really good. These both have a 10BA thread and the AG wheels need tapping accordingly. I have used the 4MA100 version on the front and rear drivers on my Bachmann Jubilees but the BR Std tank has tight clearance on the front axle and a used the brass Markits deluxe crankpin here instead.

IMG_20200223_142857186.jpg


All wheel need spacer washers 2 x 1mm each side obtained from Alan Gibson both 2mm and 1/8in variety required.

IMG_20200223_144126773.jpg


Using the stainless ones enables reuse of the Bachmann Coupling Rods but to reuse the connecting rods and cranks requires some work on the 4MA103 crankpin. Looking at the Bachmann centre axle crankpin shows this has a slot which enables correct positioning of the crank. The Markits replacement needs to be modified to replicate this slot. The first pair I did with a fret saw and thin file but I have now purchase a jewellers slotting file to do the job. This job needs to be carried out carefully so that the slot is just the correct depth and width to take the pair of 'pip's on the inside of the Bachmann crank. I have been unable to find the photo of my modified Markits crankpin. I'll post it when found.

One further modification is required as the Markits centre crankpin [ 4MA103] is 2.6mm diameter and need to be turned down to 2.3mm at the end to take the Bachmann crank. I did this by putting the slotted crankpin in a pin vice and used needle files to remove the 0.3mm required. Not as hard as it sounds.Finally this crank takes an M1.4 screw so you will need to obtain some - I sourced mine from ebay. The length of the thread should be around 2mm.

Sound modification to the slide bar support bracket is necessary which involves removal of some material to give clearance for the connecting rod.

The brakes on the keeper plate need to be repositioned 1mm further out. I cut them off and inserted a piece of 1mm plasticard. I hope these are helpful.
IMG_20200224_121100833.jpg

IMG_20200224_121243466.jpg


Hope this helps. Please feel free to ask any questions.

Robin

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Steve Carter
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Re: Rigid Chassis Locos?

Postby Steve Carter » Sun Apr 12, 2020 6:34 pm

Thanks for the informative insight into your 4MT conversion Robin. Very useful.
Take care
Steve
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Wizard of the Moor
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Re: Rigid Chassis Locos?

Postby Wizard of the Moor » Sun Apr 12, 2020 10:57 pm

Here's a converted Std 4MT in my possession, Steve. The Bachamnn drivers have been turned down and kinda spaced out a bit. The pony wheels aren't quite right, but I think I'll get away with it after a spot of weathering :?

6F3C6E7D-3E20-4DFC-9EBE-B26A1B0A884E.jpeg


3DB56913-A5AF-4DA8-A2D5-52D7B02037C5.jpeg


641808EA-9B00-4445-B358-815C2AE74EE8.jpeg


HTH,

James
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Steve Carter
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Re: Rigid Chassis Locos?

Postby Steve Carter » Tue Apr 14, 2020 11:28 am

Std. 4 tank conversions are becoming a bit popular.

Thanks for the photos and suggestions.
Steve Carter

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Mark Tatlow
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Re: Rigid Chassis Locos?

Postby Mark Tatlow » Tue Apr 14, 2020 10:23 pm

Wizard of the Moor wrote:. The pony wheels aren't quite right, but I think I'll get away with it after a spot of weathering :?



Very Ben Hur if you don't mind me saying; woe betide a Stanier class 4 tank that runs up alongside............

BH-8.jpg
Mark Tatlow

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Will L
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Re: Rigid Chassis Locos?

Postby Will L » Tue Apr 14, 2020 10:36 pm

Wizard of the Moor wrote:... The pony wheels aren't quite right, but I think I'll get away with it after a spot of weathering :?


The pony truck looks like an open spoke wagon wheel. Hiding the open spokes is going to take a lot of weathering.

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Noel
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Re: Rigid Chassis Locos?

Postby Noel » Wed Apr 15, 2020 10:20 am

Will L wrote:The pony truck looks like an open spoke wagon wheel. Hiding the open spokes is going to take a lot of weathering.


The bogie wheels are also wagon wheels [pinpoint axles again] but 10 spoke in this case. Both are therefore nominally 3ft 1.5ins diameter; the prototype's were 3ft diameter 9 spoke in both cases.
Regards
Noel


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