Gear box woes

[Tim Doran]

My GFs brother owns a narrow boat that has a most unusual gearbox set up. The old box died a slow and painful death and is not fixable even though it has been serviced. We are attempting to fit a new one.

 

The setup looks like this

 

 

He has bought a PRM80 gearbox and we have bolted it in place etc. However we did not realise that there was such a thing as left and right gearboxs. The old box must have been a right hand one and the new one is a (standard) left hand one.

 

So it is not going to work! Any suggestions other than "you should have checked it before you started"?

 

Tim

[STUBAG]

My GFs brother owns a narrow boat that has a most unusual gearbox set up. The old box died a slow and painful death and is not fixable even though it has been serviced. We are attempting to fit a new one.

 

The setup looks like this

 

 

He has bought a PRM80 gearbox and we have bolted it in place etc. However we did not realise that there was such a thing as left and right gearboxs. The old box must have been a right hand one and the new one is a (standard) left hand one.

 

So it is not going to work! Any suggestions other than "you should have checked it before you started"?

 

Tim

[Timleech]

My GFs brother owns a narrow boat that has a most unusual gearbox set up. The old box died a slow and painful death and is not fixable even though it has been serviced. We are attempting to fit a new one.

 

The setup looks like this

 

 

He has bought a PRM80 gearbox and we have bolted it in place etc. However we did not realise that there was such a thing as left and right gearboxs. The old box must have been a right hand one and the new one is a (standard) left hand one.

 

So it is not going to work! Any suggestions other than "you should have checked it before you started"?

 

Tim

 

I've been through small reverse-rotation boxes before, I think the smallest you'll get which will accept a reverse-rotation input is the Hurth/ZF 125 or equivalent, but it has to be dismantled and 'converted'. It might be possible with smaller models, you would have to check. The MC tech department (probably not technically Midland Chandlers) were helpful in sorting this out, at a significantly better price than I could find elsewhere.

 

Tim

[STUBAG]

If the reduction ratios are the same for ahead and astern, you just have to change the gear cable from one side of the single lever control to the other.....surely?

[David Mack]

My GFs brother owns a narrow boat that has a most unusual gearbox set up. The old box died a slow and painful death and is not fixable even though it has been serviced. We are attempting to fit a new one.

 

The setup looks like this

 

 

He has bought a PRM80 gearbox and we have bolted it in place etc. However we did not realise that there was such a thing as left and right gearboxs. The old box must have been a right hand one and the new one is a (standard) left hand one.

 

So it is not going to work! Any suggestions other than "you should have checked it before you started"?

 

Tim

 

Brummagem Boats' Brumtugs from the 70s used to have an arrangement something like this, with the engine under the counter and a belt drive down to the propshaft. That way there was no loss of headroom due to the shaft under the back cabin floor, and the 'engine room' housed a kitchenette and bathroom, while retaining the external appearance of a working boat cabin.

 

Easiest solution for you (assuming you don't want to go forwards in reverse gear and vice versa) might be to change the prop for one of the opposite hand.

 

David

[Tim Doran]

If the reduction ratios are the same for ahead and astern, you just have to change the gear cable from one side of the single lever control to the other.....surely?

 

 

Brummagem Boats' Brumtugs from the 70s used to have an arrangement something like this, with the engine under the counter and a belt drive down to the propshaft. That way there was no loss of headroom due to the shaft under the back cabin floor, and the 'engine room' housed a kitchenette and bathroom, while retaining the external appearance of a working boat cabin.

 

Easiest solution for you (assuming you don't want to go forwards in reverse gear and vice versa) might be to change the prop for one of the opposite hand.

 

David

 

I don't think that I have explained the problem clearly. The problem is that the gearbox will only accept a left hand input (clock wise I think) and the engine is supplying it with a counter clockwise rotation.

[RobinJ]

My GFs brother owns a narrow boat that has a most unusual gearbox set up. The old box died a slow and painful death and is not fixable even though it has been serviced. We are attempting to fit a new one.

He has bought a PRM80 gearbox and we have bolted it in place etc. However we did not realise that there was such a thing as left and right gearboxs. The old box must have been a right hand one and the new one is a (standard) left hand one.

 

So it is not going to work! Any suggestions other than "you should have checked it before you started"?

You are stuck as this gearbox only rotates one way!

Take the drive from the front of the engine, or turn the engine round?

Swap the 80 for a 150 which is reversible, but probably too big?

[Tim Doran]

You are stuck as this gearbox only rotates one way!

Take the drive from the front of the engine, or turn the engine round?

Swap the 80 for a 150 which is reversible, but probably too big?

 

 

Bother that is what I thought. I guess that the engine could be rotated but there is bugger all space to do so easily.

 

 

I have had a look at the 150 and there is mention of gearbox cooling. Would this be necessary?

 

 

I have that sinking feeling that it is going to be too difficult for us to do.

[Grace and Favour]

Forgive me - for I am not an engineer (which will shortly become obvious)

 

But if you replaced the Drive & driven pulleys with a 'flat' profile - could you not put the belt on in a 'figure of 8'

 

That would reverse the drive

[Tim Doran]

That would be a solution but is it feasible. There is about 2 foot between the engine and gearbox

[RobinJ]

I have had a look at the 150 and there is mention of gearbox cooling. Would this be necessary?

It would depend on the load, provided the temperature does not exceed the recommended (~75 I think) its not necessary.

[Grace and Favour]

Forgive me - for I am not an engineer (which will shortly become obvious)

 

But if you replaced the Drive & driven pulleys with a 'flat' profile - could you not put the belt on in a 'figure of 8'

 

That would reverse the drive

 

 

That would be a solution but is it feasible. There is about 2 foot between the engine and gearbox

 

Is it feasible with only 24" between them ? . . I really don't know Tim - - though other members with experience of belt drives may know the answer

[bizzard]

If you could fix the large drive pulley onto the other end of the engine then turn the engine round 180 degs and reconnect the belt that would correct it and make the gearbox work but the propeller would then be of the wrong rotation,you could swap the gear cable around to correct this but then the boat would then be driven forward with the gearbox in its natural reverse gear and visa-versa,which is not good for a marine or most gearboxes come to that.

 

Sorry similar to Robin J's

 

Is there room behind up against the transom to turn the gearbox around and the reconnct the gearbox output shaft to the prop shaft behind the engine.You would have fix a support bearing to the free end of the propshaft then though and change the propeller i think,hold on.

Edited February 29, 2012 by bizzard

[Proper Job]

That would be a solution but is it feasible. There is about 2 foot between the engine and gearbox

Swap the drive and driven pullies for drive and driven meshing gears. The rotation is then reversed

[Tim Doran]

If you could fix the large drive pulley onto the other end of the engine then turn the engine round 180 degs and reconnect the belt that would correct it and make the gearbox work but the propeller would then be of the wrong rotation,you could swap the gear cable around to correct this but then the boat would then be driven forward with the gearbox in its natural reverse gear and visa-versa,which is not good for a marine or most gearboxes come to that.

 

But we could replace the prop to the other direction type. IE left to right

[OldGoldy]

Any suggestions ...............

 

Is there space to set up a belt/idler/sprocket arrangement so that the gearbox runs off the outside of the belt as in the crank pulley/water pump/alternator arrangement in many cars? Would need to be a substantial set-up.

 

Just a thought!

[bizzard]

Your easiest way in my opinion is to turn the gearbox around 180-degs,if theirs room at the stern transom then change the prop.

[Grace and Favour]

I don't s'pose I should even consider suggesting a new box at £800 should I?

[Chalky]

Other options. Replace gearbox with hydraulic pump or generator. Drive pump of hydraulic / electric motor.

 

Move engine forwards, turn gearbox round,drive off belt. Shorten propshaft, drive off belt on gearbox.

 

List box on ebay with a swap for gearbox going other way option.

[David Mack]

I don't think that I have explained the problem clearly. The problem is that the gearbox will only accept a left hand input (clock wise I think) and the engine is supplying it with a counter clockwise rotation.

 

I'm not familiar with this particular box. Can it be converted to the opposite hand? Or can you swap or trade it in for one of opposite hand? Would save a lot of bother changing everything else!

 

David

[Chris Pink]

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

[Timleech]

Why does nobody listen?

 

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.

 

Tim

[Tim Doran]

Why does nobody listen?

 

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.

 

Tim

 

Hi Tim

 

thanks for the clarification.

 

Tim

[Proper Job]

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

[bizzard]

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

Like an old mangle,but keep slapping grease on the gears should surfice or better still knock up a tin oil bath.