Any Wheel and size!
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Re: Any Wheel and size!
That should just be the minimum width on the drawing, a lot of manufacturers went for the maximum.
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Re: Any Wheel and size!
Have you thought of bonding the wheels into the tyres using additional printer resin and solidifying it with a UV lamp? In doing so you can use the machining marks on the inside of the tyre to lock the printed insert in place.
Mark Humphrys
Mark Humphrys
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Re: Any Wheel and size!
David Bigcheeseplant wrote:Previously I have made the wheels a tight fit in the tyre with a bit of glue so they stay put. I have used Gibson tyres in the past but if I can get tyres CNC machined the I would design the tyre so that the centre has a more positive location. The fit I can get on an axle is similar to that of a Gibson wheel.
David
How about making the centre a sliding fit into the tyre and locking them together with Loctite 603 or similar retainer? If the tyre is turned with a groove on its inside and the centre is printed with a matching groove in its outside, then the retainer should set as an annulus that both retains the tyre strongly and centres the tyre.
Re: Any Wheel and size!
best33 wrote:Have you thought of bonding the wheels into the tyres using additional printer resin and solidifying it with a UV lamp? In doing so you can use the machining marks on the inside of the tyre to lock the printed insert in place.
That doesn't work. The cured resin is opaque to UV, meaning the joint will cure as a skin on the outside but leave uncured resin on the inside.
Re: Any Wheel and size!
Guy Rixon wrote:How about making the centre a sliding fit into the tyre and locking them together with Loctite 603 or similar retainer? If the tyre is turned with a groove on its inside and the centre is printed with a matching groove in its outside, then the retainer should set as an annulus that both retains the tyre strongly and centres the tyre.
I've never been able to get 603 to hold cured resin. Mainly, I think, because of no being able to make a small enough gap between the tyre and the centre to be truly anaerobic.
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Re: Any Wheel and size!
I have been working on the J15 printed wheels which I understand will be sutible for the Oxford N7 too but have modified it to fit a 2mm axle. The tough resin is pretty good stuff although there are supply issues.
I had a radical thought Romford do P4 axles would people be interested if I did these wheels to fit these axles too so they would be self quatering?
As the moment I cant get to my printer as it in the loft and I am limping round due to a running injury.
I had a radical thought Romford do P4 axles would people be interested if I did these wheels to fit these axles too so they would be self quatering?
As the moment I cant get to my printer as it in the loft and I am limping round due to a running injury.
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Re: Any Wheel and size!
Yippee. The J15 wheel looks good.
David
David
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Re: Any Wheel and size!
This may be the stupidest question ever asked here, but supposing one didn't need electrical pick-up from the track, could the entire wheel be 3D printed? How hard is the material?
Nick Allport
CLAG
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Re: Any Wheel and size!
It pretty hard stuff but not sure I would use it for a working surface.
David
David
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Re: Any Wheel and size!
glad up this popped back, I need some drivers for GWR Dean singles, using Alan Gibson 7' 6" tyres.
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Re: Any Wheel and size!
David Bigcheeseplant wrote:I had a radical thought Romford do P4 axles would people be interested if I did these wheels to fit these axles too so they would be self quatering?
Certainly would David!
John
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Re: Any Wheel and size!
Suggest self quartering wheels be approached with a lot of caution. There's been a few attempts over the years and in each case it has been possible to twist the assembly well out of true simply because the material is soft. Romfords are metal and Slaters saw fit to use a brass centre despite moulding the wheel in glass filled nylon which is pretty rigid stuff.
Currently, I feel quartering isn't a big issue - it's getting axle and rod centres matched and all crank throws equal. If these have drifted, then you end up fiddling with the quartering looking for that sweet spot (if there is one) and this is where it seems critical. Essentially you get a few thou' to play with and the quartering seems to come at the end of the queue.
DaveB
Currently, I feel quartering isn't a big issue - it's getting axle and rod centres matched and all crank throws equal. If these have drifted, then you end up fiddling with the quartering looking for that sweet spot (if there is one) and this is where it seems critical. Essentially you get a few thou' to play with and the quartering seems to come at the end of the queue.
DaveB
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Re: Any Wheel and size!
davebradwell wrote:Suggest self quartering wheels be approached with a lot of caution.
...
Currently, I feel quartering isn't a big issue
DaveB
I fully agree and I would add to your last point that I have often had people bring their chassis for me to look at saying they are have trouble with the quartering and 9 times out of 10 it is not the quartering!
It is a long time since I used Romfords, but from what I recall,the "square end" principle was never particularly precise and it often rquired a degree of fettling. So whilst it might work well enough for a rigid frame / rigid rods set-up typical of the era when Romfords were designed, I don't think it is anywhere near acurate nor repeatable enough for a half-decent P4 loco. Now, I am not talking so much about the quartering, but rather the resultant concentricity / wobble of the wheelset after the wheels have been pushed onto the axle. Romfords are in diecast metal - a semi rigid material is not going to improve matters with the difficulty of getting a reliable interference fit on a machined square.
I have only tried one set of Slater's wheel in 7mm and they were very good - but as you say Dave, they involve some accurate metalwork.
Plus, they are no help to anyone modelling a Gresley prototype!
But what the heck? this is a cheap-as-chips tooling-less method - so why not knock up a few dozen prototypes and see how they turn out?
Looking forward to hearing the outcome!
Best Wishes,
Howard
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Re: Any Wheel and size!
I agree about the wheel having to be more rigid when a square ended axle is involved. I know that Ultrascale did it once for a commission job where an 00 driving axle couldn't be removed from a chassis being converted, but their plastic is more rigid than Alan Gibson, for example.
However I have used several sets of modern Markits wheels in EM conversions and whilst they have been perfectly concentric, the EM back to back came out at 16.45mm. That's wrong for standard EM, it should be 16.5mm, the flange is a bit thick and the requirement was for a b-b of 16.65mm. So I mounted the wheel back to front on an axle, put the axle in the three jaw chuck and was able to gently persuade it to be completely wobble free (it was pretty good, to be honest, but here it had to be perfect) before taking a skim off the back of the flange, which reduced the thickness and increased the b-b in one go. It didn't have to be concentric in the chuck as I was only touching the back of the flange.
So they can be tickled a bit, and if the flange was in a different place on the centre they could be turned to P4 dimensions with the new form tool. Unless you were happy to put up with a wheel that is touch too wide...
Philip
However I have used several sets of modern Markits wheels in EM conversions and whilst they have been perfectly concentric, the EM back to back came out at 16.45mm. That's wrong for standard EM, it should be 16.5mm, the flange is a bit thick and the requirement was for a b-b of 16.65mm. So I mounted the wheel back to front on an axle, put the axle in the three jaw chuck and was able to gently persuade it to be completely wobble free (it was pretty good, to be honest, but here it had to be perfect) before taking a skim off the back of the flange, which reduced the thickness and increased the b-b in one go. It didn't have to be concentric in the chuck as I was only touching the back of the flange.
So they can be tickled a bit, and if the flange was in a different place on the centre they could be turned to P4 dimensions with the new form tool. Unless you were happy to put up with a wheel that is touch too wide...
Philip
Re: Any Wheel and size!
Most of the problems with Romford/Markits wheel have less to do with the manufacturing tolerances and more to do with modellers endlessly taking the wheels on and off the axles.
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