Prop rpm

[Jacq]

Can anyone tell me if an engine has a max rpm of 375 and 59 hp , is it possible to increase say 300 rpm upto a usable prop rpm ?

Either hydraulic or mechanical but it must be capable of going into reverse. No its not a typo 300 rpm. Cheers.

[NB Alnwick]

Can anyone tell me if an engine has a max rpm of 375 and 59 hp , is it possible to increase say 300 rpm upto a usable prop rpm ?

Either hydraulic or mechanical but it must be capable of going into reverse. No its not a typo 300 rpm. Cheers.

 

I am not sure why you need to change it - our engine and prop runs at between 200 and 300 rpm and this is an ideal speed on a canal. If you use a good size prop - say, 24 inch square you will get along nicely.

[magnetman]

I've seen a belt drive gearbox on a perkins 4236, triple v belts, that'd presumably work if pulleys were right and engine raised or moved to the side. I've also seen a big 6 pot offset driving a massive shaft in a dutch barge via belts.

[Yoda]

Can anyone tell me if an engine has a max rpm of 375 and 59 hp , is it possible to increase say 300 rpm upto a usable prop rpm ?

Either hydraulic or mechanical but it must be capable of going into reverse. No its not a typo 300 rpm. Cheers.

 

I'm not sure i understand the question.

 

Your engine produces 59 hp at 375rpm and you want to gear the rpm up? I would have thought that a prop rpm of 375 was very good. This might be a big prop but it would be very efficient.

[denboy]

trying to read between the line s on this one have you found an engine and need a reversing gearbox for it ??

[Jacq]

Thanks for the replys. Graham, as you know our boat is from the same builder as yours , so your reply has got me thinking.

Do you know what the maximum size prop that will fit ?

I spoke to crowthers today , and they were strugling to quote for this rpm.

They were coming up with 46" figures for the prop and 3" shaft. Which definatly wont work with the space available.

Cheers.

[Yoda]

Thanks for the replys. Graham, as you know our boat is from the same builder as yours , so your reply has got me thinking.

Do you know what the maximum size prop that will fit ?

I spoke to crowthers today , and they were strugling to quote for this rpm.

They were coming up with 46" figures for the prop and 3" shaft. Which definatly wont work with the space available.

Cheers.

 

No, you need to fit a five blade job. You can under prop it and therefore not absorb all of the power, as an alternative.

[Jacq]

Thanks Yoda. Do you have any contacts or information on this type of prop ?

[Yoda]

Thanks Yoda. Do you have any contacts or information on this type of prop ?

 

Not currently but since i'm interested I will do some research.

 

What your basically doing is adding two more blades to absorb the same power but reducing the diameter while keeping the same blade area.

 

Edit to ask if your in a hurry for this infomation?

Edited February 28, 2008 by Yoda

[NB Alnwick]

Thanks for the replys. Graham, as you know our boat is from the same builder as yours , so your reply has got me thinking.

Do you know what the maximum size prop that will fit ?

 

I believe Phil originally fitted a 29 inch diameter x 24 inch pitch prop on 'Alnwick' but, according to legend, he had difficulty steering it in a straight line so he reduced it to 24 inch diameter and still had the same problem!

 

We usually run the engine at between 250 and 300 rpm on the canal which gives us between 3 and 4 miles an hour - 350 to 400 rpm on rivers gives us abut six milesw an hour.

[DHutch]

Our engine runs at between 60 and 300 rpm, typical canal crusing around 150/200rpm.

- Straight through to the prop. With a 26in*36in oversquare prop. Crowthers. Which works very well for us.

 

 

Daniel

[Jacq]

Thanks to you all for the info. Yoda, no great rush , i will also look on the net and if i find anything i will pass it on .Cheers.

[Timleech]

Can anyone tell me if an engine has a max rpm of 375 and 59 hp , is it possible to increase say 300 rpm upto a usable prop rpm ?

Either hydraulic or mechanical but it must be capable of going into reverse. No its not a typo 300 rpm. Cheers.

 

One point to ponder even with the drive geared up, is whether you will be able to go slowly enough if the prop is matched to the full engine output.

I know that a lot of modern engines of that sort of hp are fitted into NBs, (is this going into a narrowboat?), but they (well, some of them) are able to achieve a slow enough tickover partly because the little daisies with which they're fitted are terribly inefficient, and partly because modern engines often have a wider speed range than older ones.

To be able to travel at satisfactory 'tickover speed' will need maybe only half a horsepower going through the prop. What speed will your engine go down to? A very rough back-of-envelope sum suggests to me it would need to be about 60 rpm.

 

I'm a great fan of boats having decent-sized propellors, but I honestly don't believe you will ever be able to make use of that power if it's properly matched to a good-sized prop in a NB. As has been suggested, you'll probably have an easier life with an undersized propellor.

 

If you do want to increase the shaft speed, multiple vee belts are probably the simplest option.

 

Tim

[Proper Job]

On of your biggest problems is the massive amount of torque that your engine can potentially produce.

 

If I've got my sums right its a massive 826 lbs ft or 1115 Nm. Thats a serious amount of torque for a NB.

 

If you consider that prm newage gearboxes are effectively rated by the torque they are able to deal with (in Nm), your going to need a prm 1500. You might get away with a 1000 if you promise not to use all of the torque available (something I doubt you will be able to do however you prop it). The prm 1000 is available in 1:1 format.

 

I think you will then need to 'under prop' it to make it useable at lower speeds.

 

Whats the engine?