JimH wrote: ↑Wed Jun 14, 2023 9:04 am
As for now? We've got the steel and the control systems licked so controlling it properly and making it reliable would be a breeze. We could lubricate the engines properly while keeping the oil out of the heat transfer fluid so you didn't knacker the boiler so you could build a steam lorry that worked much better but what would be the point?
Just because you can...
Thank you that was an interesting read, did anybody ever build them with a twin speed rear axle?
No. You don't really need gears on a steamer because you just spin the engine faster. All you need to be able to do is some sort of cut off arrangement to reduce the amount of steam entering the cylinders as the speed pick up. Some (like the DG and S Type) had a gearbox but that was to give you a get you out of the shit bottom gear that was selected while stationary. BTW all of this applies to almost all steam transport whether it is a waggon, a traction engine or a A4 Pacific. If you want to go faster you just spin the crank faster.
The other problem with two speed axles is that they really struggled to get a rear axle that was up to the job in the available space. The output speed of the Sentinel engine was and is much higher than the output shaft of a lorry gearbox. This meant they had to get Kirkstall to build a double reduction back axle that has a worm drive from the input shaft which drives the bevel drive. From memory most dismal waggon axles run about 3.5ish to 1 whereas the S axle is somewhere near 7 to 1. What this means is that the half shafts can see absolutely crazy torques which meant they had to be very, very much more stout than normal. The S axles are proper earth moving kit huge so trying to get a two speed axle to work under those loads would have been quite tricky.
Yes, maximum torque is at 0rpm and it is terrifyingly high.
By high I mean at full boiler pressure you are in excess of 3000lb/f. You start to understand why they would have made nice very heavy haulage tractors.
Last edited by JimH on Wed Jun 14, 2023 4:05 pm, edited 1 time in total.
Yes. Makers of high quality axles to the landed gentry. I have never found out what Sentinel paid for the rear axles. It must have been a lot of money.
JimH wrote: ↑Wed Jun 14, 2023 6:08 pm
The fastest we spun the Super was about 1750. The S crank is less stiff so we tend to limit it to not much more than 1000.
Impressive, I was thinking somewhere in the region of 500.
