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Martin Hocking
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Yeah I suppose that makes sense.
Like I mentioned in my previous post nova racing are the people to talk to if you need a motorbike gear making. It might be worth asking them. If they can’t help (they are geared up to make more metric stuff), they might be able to point you in the direction of somewhere that can.
I’ve not had any dealings with them but as I understand it they do make their own stuff.
This is their place taken from
This article in 2016.
I’m sure someone else will be along with a better suggestion soon but something to think about in the meantime.
Best of luck.
I was at the site of the 2025 Autograss National Finals today, just up from Pendine in West Speedlimitville, and spent half an hour talking to the owner and proprietor of Elite Transmissions. Talked over my requirements, outstanding issues, and have agreed next steps. So, with any luck, once I get my "best estimate" of required ratio and shaft dimensions we should be in the position of moving this forward - without me going down the road of another steep learning curve.
So fingers crossed, all I have to do is modify the mini casing to take the Yamaha gears ( and guestimate the right ratio of primary to input ratio)
So fingers crossed, all I have to do is modify the mini casing to take the Yamaha gears ( and guestimate the right ratio of primary to input ratio)
Famous last words "all I have to do"...
I've cut out the end of an A+ gearbox casing, just a scrap one that had been outside waiting to be melted down. I've started working on ratios to get somewhere near the ideal "drop gear" ratio - in doing this decided to modify the Yamaha Vmax second motion shaft to take a mini fd pinion, it's not ideal strength wise but will vastly open up the gearing possibilities.
So that's been today's job - select suitable bearings for the diff end of this shaft (based on the biggest inner diameter I could get on the shaft), I have plenty of room so decided to use two 60/28 koyo bearings, and machine the hardened shaft to remove Yamahas spline and cut the I'd of a mini pinion on the end. I wish I knew more about hardening and tempering steel shafts and gears. The shaft has machined to diameter ok, next will be deciding how to cut the coarse spline.
The input shaft will need attention soon, this needs to have a spline on the input end for the new input gear to locate to, with an overhang to locate a roller bearing. This spline will likely need grinding - that's another rabbit hole to go down for me...
I've pulled the gear selectors and barrel from the Vmax casing, the good news is there is plenty of space beneath the gear shafts for all of this, it just needs to be in the right place relative to the shafts, the plan being to make a new end plate for the bearings, selectors and barrel, then use a specially made long reach boring bar on my vertical mill to bore down through these holes and line bore them. Long way to go, involving some tig welding, spine cutting and buying in apir of gears,but I'm not seeing any showstoppers so far.
I've cut out the end of an A+ gearbox casing, just a scrap one that had been outside waiting to be melted down. I've started working on ratios to get somewhere near the ideal "drop gear" ratio - in doing this decided to modify the Yamaha Vmax second motion shaft to take a mini fd pinion, it's not ideal strength wise but will vastly open up the gearing possibilities.
So that's been today's job - select suitable bearings for the diff end of this shaft (based on the biggest inner diameter I could get on the shaft), I have plenty of room so decided to use two 60/28 koyo bearings, and machine the hardened shaft to remove Yamahas spline and cut the I'd of a mini pinion on the end. I wish I knew more about hardening and tempering steel shafts and gears. The shaft has machined to diameter ok, next will be deciding how to cut the coarse spline.
The input shaft will need attention soon, this needs to have a spline on the input end for the new input gear to locate to, with an overhang to locate a roller bearing. This spline will likely need grinding - that's another rabbit hole to go down for me...
I've pulled the gear selectors and barrel from the Vmax casing, the good news is there is plenty of space beneath the gear shafts for all of this, it just needs to be in the right place relative to the shafts, the plan being to make a new end plate for the bearings, selectors and barrel, then use a specially made long reach boring bar on my vertical mill to bore down through these holes and line bore them. Long way to go, involving some tig welding, spine cutting and buying in apir of gears,but I'm not seeing any showstoppers so far.
Martin Hocking
Member
- Messages
- 464
- Location
- Norfolk
I do like the full on approach you take to things mr mutly. You’ve done all that in the time it would have taken for me to decide this is a going to be a bit complicated and have gone to make a sandwich to think about it!
I have toyed with a similar idea since a friend of mine gave me the leftovers of a vfr750 engine many moons ago. I think I’d garnered a little inspiration from an Aussie bloke who’d managed to make a bike cluster fit into a mini sump.
The ratios in the gear cluster always seemed a little bit problematic to me. Well first gear specifically. Bike gearing is always very tall in bottom gear. That and the strength of the dogs.
I suppose thinking as I type I guess you could ditch first gear altogether and drop the final drive ratio but I suppose you’d end up with a very short top gear but I suppose that’s not too much of a concern in a hillclimb car.
So is this the earlier vmax gearbox?
I have toyed with a similar idea since a friend of mine gave me the leftovers of a vfr750 engine many moons ago. I think I’d garnered a little inspiration from an Aussie bloke who’d managed to make a bike cluster fit into a mini sump.
The ratios in the gear cluster always seemed a little bit problematic to me. Well first gear specifically. Bike gearing is always very tall in bottom gear. That and the strength of the dogs.
I suppose thinking as I type I guess you could ditch first gear altogether and drop the final drive ratio but I suppose you’d end up with a very short top gear but I suppose that’s not too much of a concern in a hillclimb car.
So is this the earlier vmax gearbox?
Yes earlier Vmax, I just "happened" to have one here. Plenty of room between the input end of the mini box and the pinion for 6 equally strong gears, not that I should need them so I'm sticking with the Vmax 5. The gearing is very close to the Swiftune first gear, and thence on gets closer and closer, so I'm basing my calcs on that or "better" - whilst admitting at this point I'm not really sure what better might be. Going to Prescott mini hillclimb later today, so hopefully will have a better idea by end of tomorrow. Trying to gear it down enough to skip first looks like not possible.
The 1st gear on the secondary shaft is a surprisingly large diameter, so large in fact that I'm going to have to relieve the casing to get it in! If I end up making a new first motion shaft I might look into raising the ratio for 1st, but we'll see.
