Gear box woes

[bizzard]

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.

? Isn't that almost exactly how i explained it?. I doubt if the smooth impregnated canvas back of an ordinary V belt would drive a waterpump without slippage unless adjusted extremely tight. Years ago on some vehicles this was done as an add-on but they had very wide and deep belts and the pump drive wheel was of large diameter and wide with heavy spring loading onto the belts back.

[Tim Doran]

? Isn't that almost exactly how i explained it?. I doubt if the smooth impregnated canvas back of an ordinary V belt would drive a waterpump without slippage unless adjusted extremely tight. Years ago on some vehicles this was done as an add-on but they had very wide and deep belts and the pump drive wheel was of large diameter and wide with heavy spring loading onto the belts back.

 

The real problem that we have is that a hydraulic setup will be over budget.

 

Ok, the combination of your posts explains it very nicely.

 

Belts are looking less feasible. So as a rule of thumb how much wrap would I need on a belt?

 

Chains are looking more feasible but I have lots of questions about them with reference to this site as a starting point.

How much contact area on a sprocket is it the same as the belt?

What type of chain would I need so that the chain would not break?

Can I use a single but heftier chain as duplex parts seem more expensive?

Anything else I should know about chains.

 

Tim

[bizzard]

The real problem that we have is that a hydraulic setup will be over budget.

 

Ok, the combination of your posts explains it very nicely.

 

Belts are looking less feasible. So as a rule of thumb how much wrap would I need on a belt?

 

Chains are looking more feasible but I have lots of questions about them with reference to this site as a starting point.

How much contact area on a sprocket is it the same as the belt?

What type of chain would I need so that the chain would not break?

Can I use a single but heftier chain as duplex parts seem more expensive?

Anything else I should know about chains.

 

Tim

Chains of course need to surround their sprockets as much as possible like belts do with pulley's.

 

And being as yours would be driving the gearbox by a limited number of sprocket teeth,i think i'd go after all for a Triplex set up ''more teeth engaged with the chain at any one time''and also a chain tensioner on a slack side to help stop any sudden kick on the chain.

You need to discuss with that company what powers,max rotational speeds and ratio's of their various chains and sprockets.

I do have this data,but all far too lengthy to type on here.

But i'd say a Triplex set up to your design would handle about 10 hp and 20hp absolute maximum,purely because of the limited amount of teeth in contact with that gearbox sprocket. That company might send you all the engineering data so you can work out what i've mentioned above for yourself.

[Tim Doran]

I have finally got the boat moving. We ended up buying a Hurth gearbox that had been rebuilt to run right handed.

 

For the first time since November we have been able to move under our own power.

 

Thanks for all the help and advice

 

Tim

[luctor et emergo]

Congratulatns Tim, well done.