Gear box woes

[RobinJ]

The smallest PRM box which has the option of reversible input is the 260. The 150 does not.

You would do better to look at a Hurth/ZF, which are similar in appearance to the PRM 80, and many of them can be set up for reverse input. Check with a ZF dealer, I found Midland swindlers as helpful as anyone and the cheapest when I needed this done last year.

I know they keep altering the numbers!, but I thought the round hydralic one could be operated in reverse by rotating the pump?

Accept that space wise he would probably be better with the hurth.

[Tim Doran]

Is it worth trying a twisted V belt before I go any further or will it not work?

 

What engine is it? Which end would a gearbox be connected normally?

 

 

I think that it is a lister sr2, I think but dont know but it

[bizzard]

Is it worth trying a twisted V belt before I go any further or will it not work?

It would work but where the belt crosses itself they will rub together wear out quickly generate frictional heat and possibly catch fire.Maybe a thin smooth shiny stainless steel plate with the edges nicely smoothed and kept lubricated with say silicon grease placed between the crossover point.Yes it would be worth a try at minimum expense anyway.

 

No don't grease it,it would make the belt slip.

Edited March 1, 2012 by bizzard

[Proper Job]

It would work but where the belt crosses itself they will rub together wear out quickly generate frictional heat and possibly catch fire.Maybe a thin smooth shiny stainless steel plate with the edges nicely smoothed and kept lubricated with say silicon grease placed between the crossover point.Yes it would be worth a try at minimum expense anyway.

Wont the grease get on the belt?

 

might make it slip on the pullies a bit?

[bizzard]

Wont the grease get on the belt?

 

might make it slip on the pullies a bit?

Yes quite,goon arn't i,ive edited it.

 

Is it worth trying a twisted V belt before I go any further or will it not work?

 

 

 

 

I think that it is a lister sr2, I think but dont know but it

If its an SR2,you can turn it right around and use the camshaft output,the shaft that drives the alternator.This shaft only rotates at exactly half the RPM of the crankshaft previously used so some serious reworking out of ratios will need doing to be comptible with your existing propeller,but rotation propeller should remain the same as the camshaft on the SR rotates in the opposite direction to the crankshaft.

[bizzard]

But i'd still say the easiest method is to turn the gearbox around if there's room up in the stern end,slip the drive pulley up the prop shaft to it. You could do this with all your existing bits. Just the propeller would need changing from l/h to r/h or r/h to l/h depending on whatever you have at the mo.

[WotEver]

Is it worth trying a twisted V belt before I go any further or will it not work?

Have you got the room to raise the back of either gearbox or engine and raise the front of the other? If so, you could twist the belt without it touching itself.

 

Tony

[Timleech]

I know they keep altering the numbers!, but I thought the round hydralic one could be operated in reverse by rotating the pump?

Accept that space wise he would probably be better with the hurth.

 

This is the 150, used to be the Delta, their smallest hydraulic box. The pump is fixed in place, can't be altered.

 

On most of those from the 260 upwards, the pump is bolted on and can, as you say, be reversed.

 

Tim

[bizzard]

Have you got the room to raise the back of either gearbox or engine and raise the front of the other? If so, you could twist the belt without it touching itself.

 

Tony

That would probably work and if both belts were crossed over he could retain the same propeller.

[WotEver]

That would probably work and if both belts were crossed over he could retain the same propeller.

Which he could call a result

[Mrs Tawny Owl]

I still recon a pair of 24" spur gears on the engine output shaft and the gearbox input shaft would be more fun to set up

 

You could even run some ancillary pumps and stuff off them

 

Might be a bit noisy in operation though

 

Couple of lorry flywheels with the starter ring gears meshed?

 

Richard

[bizzard]

A couple of appropriate size perhaps mini wheels and tyres or pneumatic tyred wheel barrow wheels,or whatever size required to bring then into contact fixed to the existing pulleys by drilling them to match the wheel stud holes and gearbox adjusted to bring them into firm contact with each other.

The only draw back would be,your grandad would need to carry a puncture outfit and pump.you could even add ABS to stop em skidding.Michelin are probably the longest lasting boots.

Ps Don't forget to have them balanced.

[RobinJ]

This is the 150, used to be the Delta, their smallest hydraulic box. The pump is fixed in place, can't be altered.

Thats the one, you simply turned the pump through 180, maybe they have changed the design on the new ones?

I think originally they were called the 120 and then later on the Delta, the 260 is a much heavier box, but mine highlites the problem as its labelled 150!

[Timleech]

Thats the one, you simply turned the pump through 180, maybe they have changed the design on the new ones?

I think originally they were called the 120 and then later on the Delta, the 260 is a much heavier box, but mine highlites the problem as its labelled 150!

 

The 120 is a mechanical box. The 260 was the 160 before it was uprated and metricated.

 

 

This list may help.

 

Tim

Edited March 2, 2012 by Timleech

[Tim Doran]

Right I think that I should take some photos to give you all some idea of the actual setup. Thanks for all the ideas so far.

 

There is room to tilt the box bit which would stop the belts rubbing.

 

Tim

[Tim Doran]

I have taken some photos of the engine but it is really hard due to the tight space.

 

Here is the belts coming off the flywheel

 

 

Here is the other end. What is here, and what was supposed to be attached here?

 

Edited March 6, 2012 by Tim Doran

[RobinJ]

I have taken some photos of the engine but it is really hard due to the tight space.

Does anybody recognise the engine from this?

Looks as though the gearbox and alternator are driven of the flywheel, hence the missing pulley on the water pump(?) at the other!

Would have thought standard V belts were not up to the job?

[Tim Doran]

Tried with a crossed belt and got a smoking belt. So that is a no go.

 

Bother this is almost back to the drawing board.

[Tim Doran]

I have been thinking about possible solutions that do not involve buying a new gear box. My latest idea would be running the box like a water pump on a car ie on the outside of the belt. I had initially thought this impossible but I did not know that you can get double sided belts.

 

Any thoughts about this idea?

 

[bizzard]

I have been thinking about possible solutions that do not involve buying a new gear box. My latest idea would be running the box like a water pump on a car ie on the outside of the belt. I had initially thought this impossible but I did not know that you can get double sided belts.

 

Any thoughts about this idea?

 

I'd say no chance.The back of a V belt has no grip hardly at all and not meant to be bent backwards,it would probably crack up in no time.Little grip also worse'nd by very small contact area on that gearbox pulley.

[Tim Doran]

What about a double sided belt such as these?

 

http://www.bearingboys.co.uk/Mower_Belts_Double_Sided-1030-c

 

[bizzard]

What about a double sided belt such as these?

 

http://www.bearingboys.co.uk/Mower_Belts_Double_Sided-1030-c

 

Still no,the contact area is far far too small on that gearbox pulley i doubt if it would turn the weight of the prop and shaft never mind drive the boat without slipping,the contact area needs to be at least half the circumference of the pulley for an as equal grip as the other pulley's.

As i keep mentioning,if there's room behind the engine can tou turn the gearbox around 180 degs,slip the propshaft pulley back

up inline with the gearbox pulley,this could be done with all your existing bits i would have thought.

Failing that two wheels with pneumatic tyres on bolted to engine and g/box and adjusted hard up against each other would grip well.

[Tony Brooks]

I have been thinking about possible solutions that do not involve buying a new gear box. My latest idea would be running the box like a water pump on a car ie on the outside of the belt. I had initially thought this impossible but I did not know that you can get double sided belts.

 

Any thoughts about this idea?

 

 

 

I agree with Bizzard but not on his grounds. The more wrap you have on a V Belt pulley the more power you can transmit before slipping. Your diagram would probably be fine for (say) a water pump where the power required from the pulley is low, but not for a gearbox.

 

I fear two idlers. One almost directly below the gearbox pulley to create a wrap of at least 1/3 of the gearbox pulley and then one above and to the right to lift the top run of the belt clear of return run. However that reduces the wrap on the engine pulley so it might slip., as may the gearbox pulley with only 1/3 wrap.

 

 

Short of a massive re-engining job involving a V drive or changing the transmission to a hydraulic system I fear you will have to shell out for a more suitable gearbox. Much as I dislike them I think I would go for hydraulics. Especially if you can find anyone who can assemble a system from off the shelf parts from any hydraulic supplier. With that belt drive there must already be a thrust block on the propshaft so you would not need a hydraulic motor that accepts axial thrust in both directions.

[bizzard]

There is of course chain drive.But i'd use double chain sprockets on all three pulley's with a duplex chain wrapped around them, keep it greased with chain lub and that wouldn't slip.

 

Or use motor cycle hefty single sprockets and single chain.

Edited March 9, 2012 by bizzard

[Tim Doran]

ah chain I had not thought of that. Might be a winner.

 

Ultimately its not my boat so not my choice