Hirth Redrive

[Echo]

Barry, I am looking at fitting a Hirth redrive to a four stroke jet ski engine,1000cc 140hp @ 7000rpm.( the motor weighs about 40 kg). Would the redrive handle that power or should I look at one thats 120hp?[?] The new project will be an open frame single seater, similar keel to my old red tandem. Thanks for any help. Eric

[asra]

Eric, the G40 should handle it OK, the one in the Kahu gyro in NZ develop about 160hp, I believe the dual seat machine Murray has been flying also is goig well, I think thats a EJ22 and also in the 160hp bracket.RegardsBarry

[asra]

The hirth box on Brian Maloney's two seat has developed some fretting around the faces. The Ej 22 developes 130hp and the heavy prop massive amounts of torque twisting.Rod Torr is developing a fix for the twisting of the gearbox and I will post photo's when it is fitted.Apart from that I think the Hirth box is up to the task.M Barker

[asra]

Not that this will help the sales of my engines but, here are some shots of a new adaption plate for the Subaru/Hirth G40 gearbox combination. This is a new development and final stages are nearly complete.Image Insert: 53.74

[Echo]

Barry, that is a good looking set-up. The jet ski option just hit a wall - no dealer will sell a new engine on its own (none that I could find,anyhow. ) Their reason was that " ....some people use them to put in aircraft..!!!" Well what a stupid thing to do! The only other option is to buy a second hand ski & rip the engine out-if I bought a ski it would end up on the water not in a gyro. Never mind. Eric

[asra]

Looks like an ea81 tucked in front of that gearbox Barry. What do you have to adapt to an EJ25?.. Pete BradleyPete

[asra]

The other models of subaru will follow.

[asra]

Echo email me with the details of the engine you tried to get and i MAY be able to get one for you, i have a couple of good contact up here, that use engines for purposes that they werent designed for.Mark

[Echo]

Thanks Bones, the best engine I've seen so far is the ROTAX engine in the GTX Sea Doo. It's a 3 cyl 4-stroke,1495cc ,155hp( the weight is roughly 50kgs-depending on what exhaust & redrive).Yamaha make a 4 cyl 4-stroke but I think it may be getting a bit long ( ie; 4 cyl in line) Eric

[Brian]

Barry, was wondering, what advantages do you see in using a Hirth gearbox to a Rotax gearbox ?They appear very similiar in the photos.You never know how far you can go, till you get there !

[asra]

The box is stronger and the cogs are 29mm wide with bigger bearings

[Echo]

Barry, as the jet ski motor idea is slowly dying, I may go with an EJ 20 or 22 ,interested to see pics/price on adaptor to suit. Cheers Eric

[Echo]

Barry, I have found a good EJ 20 ( 24000 ks '04 model) , do you have adapter to suit? Cheers Eric

[asra]

While awaiting Barry's answer to my e-mailed question about using one of these as a 'step-up-box ' I've thought of another 'silly' one. I understand these can be used as either pinion up or down but is it permissable to lie them on their side?I do have a reason for asking. The BMW K100 is fuel injected and the engine lies on its side, putting the crankshaft off centre so the crankshaft gear drives a similar gear on the clutch shaft which is in the centre. From what I can see it's not practical to try to change the ratio, but with a suitable adapter plate the drive could be brought out from the crankshaft to a gearbox lying on its side to take the output back near the midline.These are fuel injected with altitude compensation available for higher altitudes, produce 90 hp, and will do it all day and are extremely reliable. Nobody seems to be able to wear them out, and they can be bought fairly cheaply. Maximum torque is at 8000 rpm. The handbook advises against continuous operation over 8500!John EvansThink logically and do things well, think laterally and do things better.

[Echo]

John, Ive riden 2 K100,s , very smooth & nice running - until I got to 90ks then a vibration came thru the left foot peg , bad enough to be annoying but not engine destroying.This happened on both bikes at the same speed ,( different to a Harley where everything vibrates). Didnt the gyro of Newmans have a BMW engine , there was one at the museum in Wangaratta. Eric