HATZ 4L41C air cooled engine

[Amos412]

Hi would anyone be able to confirm the ratio between crank rpm and the rpm of the bottom pulley that drives the belt to the cooling fan on these?
I’d like to fit a small rpm sensor sensing a magnet on that pulley in order to monitor crank rpm.
thanks

 

[V8Druid]

Hi would anyone be able to confirm the ratio between crank rpm and the rpm of the bottom pulley that drives the belt to the cooling fan on these?
I’d like to fit a small rpm sensor sensing a magnet on that pulley in order to monitor crank rpm.
thanks

can you measure the diameters and calculate it ?
assuming the belt sits relatively equally in both pulleys ..Pi (3.142) x D will give you circumferences, then divide the larger by the smaller which will give you a reasonable idea of ratio

 

[Amos412]

can you measure the diameters and calculate it ?
assuming the belt sits relatively equally in both pulleys ..Pi (3.142) x D will give you circumferences, then divide the larger by the smaller which will give you a reasonable idea of ratio

Thanks for your reply, Yes I understand but I can’t see how the pulley that’s accessible is driven. I assume it’s gear driven off the crank but the gear mechanism is behind a cover and would mean a fair bit of disassembly to view it.

 

[Gecko]

I assume it’s gear driven off the crank but the gear mechanism is behind a cover

Mark the pulley with a paint pen (so you can actually see it) and turn the crank from TDC to TDC (multiple times if necessary)

 

[Mick-the-fitter]

What’s it in? Photos?

 

[Mogman]

Hi would anyone be able to confirm the ratio between crank rpm and the rpm of the bottom pulley that drives the belt to the cooling fan on these?
I’d like to fit a small rpm sensor sensing a magnet on that pulley in order to monitor crank rpm.
thanks

Isn’t it not the same, bottom pulley on the end of the crank or I’m I missing something

 

[Mick-the-fitter]

Like this! It’s what we called a silent pack engine to me the reduction looks a bit more than 2-1?

 

[V8Druid]

Like this! It’s what we called a silent pack engine to me the reduction looks a bit more than 2-1?

used to have a twin lung silent pack on my Elin welding genny ... never needed to have the covers off it though

 

[Amos412]

Yes that’s it exactly very same engine.
Thanks for all the replies
It’s driving a big hydraulic pump.
The pulley is not mounted directly to the crank it’s definetly offset.

 

[Mick-the-fitter]

Geared down by the look of it, 1:4 probably?

 

[Amos412]

hi just to confirm if anyone else ever needs this information I disassembled the drive end and the bottom pulley of the Air cooling fan belt to crank ratio is 1:1
Thanks everyone for input

 

[Mick-the-fitter]

hi just to confirm if anyone else ever needs this information I disassembled the drive end and the bottom pulley of the Air cooling fan belt to crank ratio is 1:1
Thanks everyone for input

Really why such a large gear case, or has it an idler?

 

[Amos412]

I marked and turned the flywheel at other end and the bottom pulley at other end definitely 1:1
It’s definitely not in line with centre of flywheel so must have a gear behind the cover

 

[Gecko]

It’s definitely not in line with centre of flywheel so must have a gear behind the cover

Do the pulley and crank turn in the same direction, or opposite?
This will tell you if there is an idler gear in the case.