MZ Diesel gearbox....

Gearbox questions & answers etc..

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Old smokey
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MZ Diesel gearbox....

Post by Old smokey » Fri Aug 03, 2018 8:59 am

I Have an old MZ ETZ 250/251 as a basis for my project

And I have a small hats diesel (1B20 or 1B30)
But need a gearbox

Now sitting in my shed I found an old Peerless 700 series mower gearbox which are popular for racing with 15hp Briggs engines etc

If I turn on its side and seal it up, I thought about a vertical belt to a shaft and then to engine and use a belt clutch.....

Any thoughts?

The box has chain drive output sprocket already!

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Re: MZ Diesel gearbox....

Post by Diesel Dave » Fri Aug 03, 2018 3:46 pm

All sounds good, what’s the range of ratios available In the gearbox?

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Re: MZ Diesel gearbox....

Post by pietenpol2002 » Fri Aug 03, 2018 8:50 pm

-

Do check out this lads experience with a Peerless behind a clone.

https://www.youtube.com/watch?v=QsRx-1XIfAs

-
Ron

Old smokey
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Re: MZ Diesel gearbox....

Post by Old smokey » Fri Aug 03, 2018 10:10 pm

I have the ratios somewhere but worked out it should work ok

And that's interesting build!

But seems a bit complicated....

CVT on engine then driving a 5 speed box?

Main thing I need to work out is clutch and find a pulley to fit engine.....

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Re: MZ Diesel gearbox....

Post by Old smokey » Mon Apr 13, 2020 3:11 pm

Still haven't had free time to start my build properly!

But finally, with this whole lockdown, I have!

I've got the MZ ETZ251 frame
A Hatz 1b20 4.8hp diesel

And 2 possible setups for gearboxes

I can either:

1 - Use the Peerless with reverse removed, engine mounted longitudinally, with peerless behind and either centrifugal or belt tension clutch
Then chain to back wheel
Fair simple but doubt it would do much more than 40mph

2 - 50cc scooter CVT
1:2 ratio from engine to cvt input, cvt then would be running double the engine speed (so the 60mph at 6000rpm would be 3k on engine) which on donor was 60mph at 6000rpm

The hatz 1b20 makes 50%more power than the scooter 50cc and 3 times the torque

So even with the crude calculation of gear ratio halving the torque (I know it's not quite that simple but it's a rough idea), it would still have more torque than the scooter so should be able to pull the ratio

I have the engine, cvt, frame, so only few other bits needed

Oh and if I just modify the 50cc crankshaft (fitting a sprocket for hatz to drive it), then It would also retain the scooter stator to charge a battery

And based on the hatz data sheet it should be possible to reach 200mpg

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Re: MZ Diesel gearbox....

Post by Diesel Dave » Mon Apr 13, 2020 4:38 pm

I think you need to be a little realistic with your expectations... the Greaves 6.5 HP that RE used in the factory Taurus diesel couldn’t top 40 on the flat.

The scooter transmission seems promising, be careful with the idle speed as the Hatz motor will still idle over 1000 rpm and with the upgearing this may be enough to start the centrifugal clutch and variator weights on their journey transmitting power.

All sounds good though!

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Re: MZ Diesel gearbox....

Post by gilburton » Tue Apr 14, 2020 1:30 pm

Forget the scooter cvt as they are set up for high revs and will need some modification to fit.
Best option, if going the cvt route is a comet cvt/drive they sometimes pop up on ebay or you can get them from here in the UK.
They can advise on the best one for power and to suit the shaft size.
https://www.ebay.co.uk/itm/Go-Kart-Wake ... OSwopRYd2B~

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Re: MZ Diesel gearbox....

Post by Old smokey » Tue Apr 14, 2020 7:48 pm

I am being realistic with the speed I am hoping for

The greaves and the custom bikes using 8 to 10hp diesel engines only do 50 or so due to gearing and low rpm of the diesel

What my idea is proposing is to use the diesel, but simulate the moped 2 stroke rpm at the cvt input using a chain and sprocket set so at 3000rpm engine speed, the cvt input would be 6000rpm

I can change rollers and springs in moped cvt to alter the engagement rpm, but as standard most dont actually move until 4000rpm plus and with lighter rollers I've ridden 50cc scooters that dont set off until 6000rpm

And I know the comet 40 is a popular cvt to use, but I have a tiny budget, and with current climate, I am off work and need something to do!
I have the frame, engine, moped CVT, and tools and various pieces of steel, and some chains/sprockets as well


So yes I fully agree the comet 40, etc is the easy way, been done many times before.....

But wheres the fun in that? Plus isnt that why we are all on here? Because we like to think outside the box?

I remember reading about Mouses VW diesel, no gearbox at all! Crazy idea but it worked!



So Moped CVT will require modifications and to be driven via chain from hatz
But that's just something to do!

4~5hp is enough to do 60mph, plenty of 50cc 2 stroke scooters manage it, because the engine is making that power at 6000~7000RPM, and my 50cc scooter would do 50mph at 5000rpm (few years ago!)

but if the diesel was direct drive to the CVT, it would be say 3600rpm max, so at maximum ratio it's only got half the top speed (like a lot of conversions with comet 40s etc, it's the engine speed that limits top speed)

So with a 1:2 ratio, the engine at 3000rpm is then simulating the ped engine at 6000rpm
Idle on the hatz is 1100rpm I believe so, cvt idle speed would be 2200rpm

The torque output would be theoretically halved by that ratio, but the hatz produces 10.5nm peak, dropping to 9nm at 3600rpm which even halved is 5.25nm dropping to 4.5in
By contrast, the standard ped engine makes 3.5nm at 5500rpm

If I can creep the engagement rpm as low as possible with heavy rollers, say 4000rpm cvt input, that 2000rpm at the engine, around peak torque

My idea is to cut away some of the crank casing, and then chain drive the old crankshaft, which then spins cvt etc, plus has the stator on the other end to charge a battery etc
Output drive (ped rear wheel spindle) can then have a sprocket fitted, and working out rpm of output shaft at 60mph, and the rpm of the mz back wheel at 60mph, means I need a 38t sprocket on ped output driving the 48t mz rear

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Re: MZ Diesel gearbox....

Post by Diesel Dave » Wed Apr 15, 2020 9:26 am

Old smokey wrote:
Tue Apr 14, 2020 7:48 pm
I am being realistic with the speed I am hoping for

The greaves and the custom bikes using 8 to 10hp diesel engines only do 50 or so due to gearing and low rpm of the diesel
I’m going to disagree with you here, in my 15 years of riding Greaves and Yanmar clone motors - believe me 10hp will only just get you to 60 on the flat if your gearing is spot on.

I’d say go for it with the CVT though, I’ve had both a Gilera ICE with a 70cc Hebo kit and Metra padded crank, that would rev to 14,000 and top 60, also a Runner 180 with malossi kit and expansion chamber. Also a first generation TMax, various Honda 250 scooters, and a rather scarry handling Hexagon with the air cooled 180 stroke motor.

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