Gear reduction

[billio]

Hi
I have a problem I am currently involved in building a V-twin from scratch with OBR racing.
To test the engine we will be using it on our university Dyno however its shafts and bearings are only limited to 10,000Rpm and we need to 'rev' the engine to around 13,000Rpm. I doubt i am the only person who has an engine to powerful for a dyno, so does anyone know of a gear reduction mechanism that would help???

many thanks Billy

[Nick3point2]

Too powerful? Just a rev limit issue surely?

[billio]

yes is it however ive been asked to find a gear reduction mechanism so that they can rev the engine to its full power to check the perfomance with out busting the dyno... any ideas?

[zac510]

Often there's a gear reduction mechanism attached to the back of the engine already

[billio]

the gearbox is not going to be ready intime and we need to check the engine so i need gear reduction mechanism that will go from the engine to the dyno

[PhillipM]

Plenty of firms make little drop-gear transfer boxes in the UK, one of those might be suitable.

[davepoth]

Lots of people do dyno runs that don't go all the way up to the redline because of dyno issues. Assuming you aren't looking to find out peak power, (and if it's a scratch built I wouldn't on the first run) you can just rev it to 10,000. If it's not grenaded by that point I doubt 3,000 more revs will make all that much of a difference.

[billio]

Phillipm do you know of any firms?? a website maybe that i could look at?
yes i understand what you mean its what i said to the 'boss' but thats what he wants so ive got to find away around the problem.

[100SRV]

What about either Rakeway, Milner Off Road or use a Land Rover LT 230 transfer case which has ratios of:
High ratio
1:1
1.2:1
1.4:1
1.6:1
Low ratio (irrespective of high ratio)
3.321:1

I have PM'd a friend who has worked with dynamometers since he left school, he might be in touch...

[billio]

Thankyou for your help. Yes that would be helpful i will keep on checking the forum for him, i will do some more research into it thanks.

[Woody306]

Hi, Yes I have been involved in Dynos for many years - there are several things you can do, but your first post says your engine is too powerful, do you mean this? if so then there is not much you can do if the motor is bigger then the dyno can absorb as a maximum.
If it is speed limited or not matched to teh profile of the dyno then either a Gearbox or even a chain drive can be used. Which University? what Dyno? - Hydraulic dynamometers can be abused a little depending on water temperatures - Eddy Current machines cannot be..

Paul

[billio]

Hello
I am from Oxford Brookes university, its not that its too powerful its just the speed limitations.
the dyno we have is the new eddy current dyno, manufactured by shenck, model w130, max power 130Kw, max speed 10,000Rpm
I am not sure what gearbox could be used, but the manager of the production would preferably like some sort of gear reduction box as he is not sure that a rear wheel drive gear box will last throughout all the testing despite what i say.

[davepoth]

What sort of torque figures are you calculating you will make? If it's going to be around that of a sports motorcycle a second hand bike box is bound to last for the few dyno pulls you'll need to make provided you only open it up in the highest gear possible while sticking to the rev limit.

[slinky]

Have a chat with the guys at compact orbital gears http://www.compactorbitalgears.com/ .. They may be able to assist..

[Nick3point2]

What torque is the engine likely to produce and what is the torque limit of the dyno? Remember any speed decrease will give a corresponding torque increase.

This isn't for formula student is it?

[Woody306]

slinky said:

Have a chat with the guys at compact orbital gears http://www.compactorbitalgears.com/ .. They may be able to assist..

This will be an expensive solution, your better off with a simple jackshaft and chain drive with suitable ratio to being the speed down into the dynos running range - 2:1 would be a good starting point - chains and sprockets will be easy to source and much more simple than a gearbox and various adaptors/shafts..

Paul

[anonymous-user]

or you could take it to a different dyno, one that is already setup to run high rpm motorcycle race bike engines for example. May be cheaper and faster to achieve than modifying what you have there.

[anonymous-user]

I designed/built a dyno system that uses a toothed belt and does over 130kW at up to 20krpm........

(look up the usual belt manufacturers, 100 odd kW and 10krpm is no probs at all ;-)