So after another long chat and some research and educated guesses from BGH Geartech, we have a planned spec for the gearbox – a type 9 Ford box, with large roller-race laygear designed for high-torque road/race applications…
This is being mated to a Ford Escort back axle with a 3.89:1 diff which, combined with the 14″ wheels should mean that we’re hitting 70mph at around 3-3.5k rpm… Looking at the power/torque graph that looks about perfect 🙂
They should be starting work on the box soon – as the car’s at JLH Minors being stripped in the next few days. I wish we were going straight into the electric conversion at this point, but getting the car mobile again is the first priority as we work towards being in the USA!
However, when that NetGain motor goes in there are some caveats:
‘…it is very hard to guess what is really happening [with] the motor, as the graphs are incomplete […]the graph shows nothing below 1000rpm and 100 Fl/Lb of torque at 96 volts. […and there is very little information…] about running this electric motor at 120 volts apart from it produces 82 HP and 152 Ft/Lbs.
[…]We know that the gearbox will happily take the power and torque if being produced from a normally fuelled engine, but high torque at low revs is not good for gearboxes. [High torque with low revs] has a tendency to bend gear teeth and over a period of time the metal fatigues allow the gear teeth to snap.
So in our opinion the gearbox will cope with the power with out any issue. On the other hand the torque need to be controlled.
If a soft start system can be used below 2000 rpm which limits the huge amount of torque that will preserve the life of the gearbox.
Obviously a clutch will have to be used to change gear and may be running the motor and using the clutch to pull away may also help the gearbox…’
So. With those caveats in place, and a suitable controller, it looks like we should be okay. But we’ll need some careful configuration of the motor controller to make sure we don’t just shred the gearbox and axle.