Prop calculation.

[Jacq]

Hi,

Could anyone help with a prop calc as I seem to have over proped the Kromhout.

Its a single cylinder producing 22hp at a max revs of 440 rpm.The engine is 10 litres ,direct 1:1 drive.In a 70 foot narrowboat of around 25 tons.

 

Any thoughts ? Cheers.

[Proper Job]

That's a huge amount of torque - even with a 1:1 box

 

I'd have thought it would have been quite difficult to over prop.

 

What blade is on it at the moment?

 

What makes you think it's over propped

[Jacq]

Ive got a 28 x 25.5 inch.With forward engaged it wont pick up above tick over.With partial forward it will pick up.

[mykaskin]

Hi,

Could anyone help with a prop calc as I seem to have over proped the Kromhout.

Its a single cylinder producing 22hp at a max revs of 440 rpm.The engine is 10 litres ,direct 1:1 drive.In a 70 foot narrowboat of around 25 tons.

 

Any thoughts ? Cheers.

 

I'd guess somewhere around 28 x 8 from the HP, but I'd guess that the extra torque available should increase that somewhat (by double at least I'd say). Are you sure it's working OK, as you should be able to get more speed over "tickover" before it starts to bear down. Are you getting black smoke, whats the fuel rack doing?

 

Mike

[Tony Brooks]

Ive got a 28 x 25.5 inch.With forward engaged it wont pick up above tick over.With partial forward it will pick up.

 

Does it have an alternator fitted and if so is it highly geared up. It is not unknown on trad. type engines for a largish alternator at idle to be developing maximum output and preventing the engine revving - probably no help.

[Jacq]

This is the quandry.A knowlegable friend has looked at the injector nozle,which is detatchable,and recons its been modified over the years (1925) and may not be spraying correctly.It starts easily ,would an incorrect spray patern reduce performance that much? I need to play with it a bit more next week.

 

Thanks Tony, but no alternator.

[Jacq]

Ive been given the Kromhout spec sheet.They used one size for each engine regardless.

Can anyone make head or tail of it, to come up with a size for the M1 model ?

 

[by'eck]

M1 prop 27.5 x 23.5" 3 blades - the BAR is in there somewhere as well

[Jacq]

Cheers , Thankyou.