Hello Gentlemen, Does anyone know why British Tanks such as, Cruiser Mk111/1V, Covenanter,Cavalier, and Centaur had round indentations or holes in their rubber road wheels? Was it to save weight? It has always puzzled me. Hope you can inform me? Many thanks, Colonel Durnford.
Good question. I always thought it was a Christie thing to give the tyres a little give in the overall aim of a smoother ride, but now you mention it I don't really know. Not just cruisers: M1928 (1931?) T34
Secondary thought, after much looking reveals nothing other than suggestions they went 2/3 of the way through: Might they have played a part originally in the 'convertible' mode when the vehicles were envisioned as sometimes running without tracks? Strong enough for track use, & just enough give for trackless? Pneumatic tyres on T3e2: T29 running trackless: BT7 Dual running compromise?
I also assumed it was for 'give' but could cooling of the tyres be another possibility? It's probably not for wear indication... Are there Christie patents that might have the answer?
The holes are there to both impart softness in the tyres, and to prevent heat build up. You can see both principles in action in modern day airless tyres, e.g. here.
Hi Guys, thanks for the information, I reckon you could be right about the heat build up within the tyres. Colonel Durnford.
Now that is a good question. I missed out in a previous post, the Crusader Tank had indentations in their tyres too.
I think they were a carry over from the original Christie design, which could run trackless. The trackless running of the Christie was much faster than when it wore tracks, so the holes in the periphery of the wheels would have been more critical. This feature was carried over to the wheels on the early Cruisers as a matter of course, and would still have had at least some benefit, but it could not be continued with the Cromwell because this was a substantially heavier tank. Early Cromwells were fitted with perforated tyres, and the decision to go with solid tyres is reasonably well documented, although I can't remember exactly where at the moment. It probably coincided with the decision to change the final drive gear ratio, which lowered the top speed from ~40 mph to ~32 mph.