Triple M

Has anybody ever seen a drive like this? It looks homeade it has a centrifugal clutch attached to the primary drive pulley. If it works good (we'll see when the ice comes off the ponds) I may try to build one.

Justaddwata

My Feedback: (3)

There have been a few belt drives like that around for years. I think belts loose a little more power than gears personally. Also that being an overdrive - going to rob extra power. Direct drive or clutched drive is going to be your better bet.

Believe It

curious why is that?

soundguykaraoke50

LOOKS LIKE THIS HAS A CLUCH AND OVERDRIVE.REALLY KOOL.ALSO LOOKS LIKE A 40cc MOTOR.DOES THE MOTOR HAVE STAMPED ON IT MADE IN U.S.A.?

Justaddwata

My Feedback: (3)

While the belt shown is toothed and not a Vee groove (V Groove being a friction belt and certainly a consumer of some energy) I believe there is generally more wear and movement going on in a belt than between gears. Belts (even toothed) will also require some degree of radial tension to prevent slipage. While gears do exert a radial load I am not sure it would compare.

Again - just my own belief - May not have any science to it

It looks like the unit shown has both a gearbox and belt overdrive. Looks a beheamoth and more weight than the power may deserve.

Heres a pic of an MH$ preped Polini motor I have running an overdrive gearbox (42% overdriven). Should boost RPM but knock down shaft HP from 10 down to around 5hp.

Triple M

I am not an expert but with a gear ratio of about 3:1 I would think that the extra RPM's generated to the prop would make up for a little lost power due to extra shaft, pulley belt, weight etc. The motor is a little unique made in Canada EH! It was made by PETCO a small company that has since gone "belly up" Can't find any info or parts for it so if it breaks- in the trash it goes. Apparently this unit is supposed to go 48 MPH thats what he was told-it is my brother in-laws boat .

Justaddwata

My Feedback: (3)

Not likely. if your claiming a 300% overdrive then you are probably going to see a 400% power loss (around 1/4 the motors HP reaching the prop. Consider a motor running 8hp (not that I think it is what your Petco will be delivering - just an example). That would leave you 2 hp to push all that boat around.

The Polini I have above uses the gear ratio to allow for a more realistic sized prop to be driven behind the boat. The motor runs 10hp and around 16000rpm. Not many hulls would appreciate the prop torque that you would see from such a configuration. Increasing rpm a little and dropping off some HP will allow me to turn a 70mm prop at a good RPM while having sufficient power to get the boat moving.

Triple M

I'm going on second hand info. By the sounds of it this drive is not a 3:1 ratio. What you say makes sense, but it is amazing the amount of HP loss. Do you know how much speed you will gain with your overdrive set-up? is it expensive?

Justaddwata

My Feedback: (3)

The setup on the Polini is not so much to make speed but rather to make the power from the motor more usable.

If you consider it is going in a Deep Vee. The 10hp motor running direct drive would likely turn an 80 - 85mm prop. A prop that big is going to also tend to turn (roll) the hull a little more (more leverage to blades of that size).

Running a 42% overdrive with the motor will boost prop speeds from 16000 to around 22000 though drop hp from 10 to around 5 hp (rounding down for gear and bearing drag). With that I will be able to run a smaller 70 - 75mm prop. The smaller props are also far more common / plentiful.

I am not sure the boat will be quicker - it may end up a little slower however should be a little more stable and easier to control.

I have other boats running counter rotating dual output shafts for similar reasons (more control - perhaps less speed).

As for price. The motor/box is from MH$. They are not cheep but at least their service is poor.

patriktegelberg

Hello

While gears and belts cause increased friction and changed efficiencies, the gearing itself does not reduce the power output to the prop. I am very interested in listening to the arguments as for why a gearing ratio of 1:A would cause a power reduction as a function of 1:A.

Regards Patrik

Believe It

you're right... there definetely is more movement going on as cog belt generally moves front/back while running. With that kind of setup (generally known as a "Cog" pulley setup) there is 0 slip unless it starts eating teeth. It also depends on what kind of belt you are using as to the kind of tension needed. A regular "rubber" belt will need the tension as they stretch.. a "polychain" belt which is actually like a plastic really needs no tension, as it forms to the shape its running. Top Fuel dragsters/funnycars/even the boats run polychains and you can usually walk right up and take the belt off. If you could find someone who can make one small enough they would be the ticket for applications like this... the downside is they just do alot of damage when they break.

I see no reason you could not get the same outcome as using gears with a cog pulley setup so long as you get the pulley tooth combination 'correct'.

Justaddwata

My Feedback: (3)

Patrik, An overdrive will absolutely reduce power at a rate closly proportionate to ratio. If not - then why dont we just drive around in overdrive all day on the roads.

patriktegelberg

There seem to be a difference in the terminology of what we call power here. The torque to the prop will change as the gearing ratio, the power will not. Power is torque times rpm, as the torque is reduced through gearing the rpm is increased and the power stays the same. Deal?

glennb2006

With transmission losses due to friction......

Deal.

Glenn

ryan_t888

Guys,

HP is only lost through the added friction of the gear drive/belt drive/chain drive. When using a gear ratio of some kind only torque and RPM are changed.

Let's use some numbers

The formula for HP - HP = ( Torque x RPM ) / 5252 Our example motor has 5HP @ 10 000RPM and we are using a 1.5:1 overdrive ratio.

Using the formula, torque = 2.626.

Now divide the torque by our OD ratio = 1.75 and our increase in RPM from the OD ratio is 15 000RPM. We sub in our new values and solve for HP.

HP = ( 1.75 X 15000 ) / 5252
HP = 4.998hp

Power can not be destroyed! It is only absorbed by friction. If a certain amount of power goes in, the same will come out minus friction and any other inefficiencies.

Ryan

DaveMarles

In a simple one step gear like that you will only lose about 5 to 10% in gear losses and often less with a belt drive.
Dave

Triple M

This is getting confusing! I think we are going to try running the boat with the set-up as is (like the picture shows) then we might make the shaft come right from the clutch, and see what happens- Old school way!!! I'll update this thread after that time. Thanks for all the input.

Justaddwata

My Feedback: (3)

Be interested in hearing how it goes. Is this destined for the apache hull you recently posted pic of?

Triple M

Yup