Steel rims/ tyres on cast iron driving wheels

[neathabbeyironworks]

What are the pros and cons of using steel tyres or rims on cast iron driving wheels?

[92220]

Mild steel rims on cast iron wheels are fine. The steel rims will last much longer than CI rims, before needing to be re-machined. The rims can be fitted as steel blanks and the rims machined insitu. That way they are guaranteed to run true to the wheels. They can be fitted using Loctite Retaining Compound, but also use a small, (around 3mm) socket grub-screw, half in the steel rim and half in the CI wheel, on the insides of the wheels, where they are hidden from general view. That arrangement is a bit "belt and braces", but you won't ever have problems with the rims coming loose on the wheels, in service. It

Bob.

[weary]

Another 'pro':
Steel tyres have greater adhesion over cast-iron tyres.

[chrisb]

An alternative to Loctite and scotch keying with a grub screw is to shrink fit the tyres in place in the same way as full size or a starter ring gear is fitted to a car flywheel. I am looking at doing this to my 7 1/4” Wren, she’s an old lady and the wheels are quite badly grooved.

[92220]

Shrinking the tyres onto the wheels is good for larger size wheels but it becomes much more fiddley with smaller wheels because the tyres don't expand as much and so accurate machining becomes much more critical. The advantage of Loctite, with the right compound, is that it is considered similar to a shrink fit in engineering. Using the grubscrew, as well, is really 'belt and braces'and is just a safety feature.

I remember when the company I first worked for as an apprentice draughtsman, did some tests with Loctite Retaining Compound, back in the early 1960s (Nowadays Loctite 648) fitting a 1.1/2" ballrace into an aluminium housing, and left it 24 hours to cure. We then tried to press the ballrace out of the housing while pressing on the outer race. It would not move under a 3 tonnes load. In the end we tried it in the 10 tonne flypress. It still would not come out with just an axial loading. It ended up that the only way we could remove the bearing was to be really brutal, with the flypress, until the bearing shattered.

Bob.

[chrisb]

Bob,
What sort of lower limit would you put on size for shrink fitting? I think I will end up with about 5 1/2” inches once I have turned the wheel centres down on my Wren.

[weary]

I have fitted shrink-fit steel tyres on cast iron centres down to 5 1/2" diameter wheel centres no problem. Steel rims (approx.) 1/2" thick (i.e. difference between inner and outer diameters). Just needs accurate machining and confident action during final fitting of rims.
I fitted using 1 thou + 1.5 thou per inch diameter interference. I heated the rims using a gas (propane) flame until they were 'very hot'= just below faint red and they were a loose fit upon sliding over the hubs but tightened really well upon (natural) cooling and seem solid without any other retention/security methods. Final fitting must be done with confidence and promptly as heat-loss and conduction is fairly rapid.

In my experience one could go significantly smaller - however, the smaller the diameters the less forgiving of 'errors' in machining/measuring and any hesitations whatsoever in final fitting. The smaller the mass of the parts the quicker the heat-loss and heat transfer.

Regards,
Phil

[uuu]

Looking up the coefficient of expansion of Steel - it shows as 0.0000065"/(in x deg F)

So for a 5.5" rim, that is 0.00003575" for each degree F.

400 degrees, and the expansion is 0.0143"

So you can get it to grow 14 thou in a domestic oven. And Phil's dull red is about 750F - grows about 26 thou.

Wilf

[92220]

Would seem I'm, perhaps, a little over-cautious!!

Bob.

[RGR 60130]

I wrote a bit about fitting steel tyres and lessons learnt here:

modeleng.proboards.com/thread/11467/new-peppercorn-blue-peter-gauge?page=2

Reg

[Nigel Bennett]

With shrink fits, some kind of axial location is advisable, such as a rebate on the tyre and wheel centre so that when you drop the tyre in position it ends up in the correct place. Last one I did was for a Maisie that had been dropped on some concrete and a bit of flange had broken off. Fitting a tyre was by far the simplest and easiest option - and it didn't spoil the paint job. Both my Tom Rolt (with tiny wheels!) and Ashey the IoW O2 have steel tyres on cast iron centres to give a bit more grip. And verisimilitude.

[92220]

Aug 21, 2023 4:28:43 GMT chrisb said:

Bob,
What sort of lower limit would you put on size for shrink fitting? I think I will end up with about 5 1/2” inches once I have turned the wheel centres down on my Wren.

Hi Chris.

I've not used shrink fit for many years. I still prefer to use the strongest Loctite.

On a wheel that measures exactly 5.500" dia, I would make the tyre 5.493"/5.495".  That is a 2 to 5 thou interference. For fitting, the tyre needs to be heated in a domestic oven to maximum oven temp. which is likely to be 200C to 220C To ensure it has expanded the maximum, allow it to soak up heat for at least 1/2 an hour. Don't forget if you do use a shrink fit, make sure you have a machined step to act as a 'stop' to fit the ring correctly, and not at a slight angle. 

Bob.

[neathabbeyironworks]

Thanks to everyone for the advice. Steel tyres, it is. Interestingly, the prototype, William Francis has bolts in the rims to hold the tyre. The tyre also has a lip that locates the tyre on the wheel.

[andyhigham]

Aug 19, 2023 12:08:02 GMT neathabbeyironworks said:

What are the pros and cons of using steel tyres or rims on cast iron driving wheels?

The default should be steel tyres. I've seen too many treads worn concave and chipped flanges

[britannia]

Definitely go for steel tyre. Good reason - is the £ cost of the casting these days (huge!), and lack of availability last time I needed some. I had the ring blanks made by a company called M Machine ([e-mail]) 01325 381302 ask for Andrew.