Clark Bobcat 300 perhaps 313

[farmer.palmer]

Hi
I have recently purchased this old Clark Bobcat 300 machine which has been partially restored and seems to work ok. But I noticed the belt which runs from the engine to the chaincase input shaft and over the top of the oil pump gets very hot. The hydraulics seem very slow too so I tightened the belt up to stop it slipping on the pump pulley. This helped the speed of the hydraulics but the belt needed to be very tight to work properly and got hotter.
I looked at this and thought it was a pretty rubbish design to drive the hydraulic pump as very little of the belt actually came into contact with the pump pulley.

I then got hold of a parts manual for the 300 and realised there should be a shorter belt underneath the longer one which just runs the hydraulic pump direct off the engine on the same pulleys. See attached screenshot from the manual item 33. Is anybody able to advise me on what length and size or profile this belt needs to be? I have asked at Bobcat and they advise that it is no longer available from them. I suspect its the same size as the 313 machine perhaps?
Thanks
James

 

[brdgbldr]

You could try taking an old belt that fits into the "V" of the pulley properly (If it is even a "V" belt). Then cut it to length and measure it. I have done this in the past and it should get you close.

 

[farmer.palmer]

You could try taking an old belt that fits into the "V" of the pulley properly (If it is even a "V" belt). Then cut it to length and measure it. I have done this in the past and it should get you close.

I don't have the shorter of the two belts on the machine. It was like this when I bought it.
Thanks

 

[ziomster]

@farmer.palmer you have wheels with space for additional belt?
have same model and i have space only for one belt and to be honest there is not that much space for additional one.

i have same feeling that this one belt has to small contact with oil pump wheel and my idea was o use double sided belt and put it under the wheel

i'm strugling with falling engine rpm when i'm starting using hydraulics and i wonder if the reason is on the hydraulic side or beacuase of engine (i have non original Ruggerini diesel engine which in spec has even more hp than original) - any ideas what could that be?

 

[sLarsen]

@farmer.palmer there should only be one belt.
I have the same unit with only 2 owners before me and there has been no modification to the machine.
What I have found is that I need a short V-belt and make sure that it aligns perfect with the 3 wheels.
Next is to ensure that that you get as much angle on the wheel for the pump (get it as high up as possible) and move the motor as close as possible to the wheel for the oil pump.
If you do not do this the V-belt will glide when you use the hydraulic and putting pressure on it. The it get V-belt get hot and you loos power in the hydraulic.

 

[farmer.palmer]

@farmer.palmer you have wheels with space for additional belt?
have same model and i have space only for one belt and to be honest there is not that much space for additional one.

i have same feeling that this one belt has to small contact with oil pump wheel and my idea was o use double sided belt and put it under the wheel

i'm strugling with falling engine rpm when i'm starting using hydraulics and i wonder if the reason is on the hydraulic side or beacuase of engine (i have non original Ruggerini diesel engine which in spec has even more hp than original) - any ideas what could that be?

Hi
Sorry I did not see your reply unitl slarsen sent me an email and I checked in.
Yes the pulleys are deep enough to run two belts. The bottom shorter belt runs from the engine pulley to the oil pump pulley, and the top longer belt runs in the same engine and oil pump pulley and onto the gearbox pulley. It sits on top of the shorter belt mentioned above.

They are shown in the manual if you have a copy of it. When I first got the machine it only had one belt and no matter how much tension I put the belt under it would slip on the oil pump pulley when under load, and the hydraulics would be very slow. It was only when I read this thread that I realised there were supposed to be two belts and the depth of the pulleys reinforced this idea.

One I got the right belts and got them under some decent tension it transformed the machine into something that I now realy enjoy using. Before I couldn't move and use the hydraulics at the same time as the belt would slip and overheat really quickly. Now I can move and use hydraulics for several hours without any problems.

Slarsenhas written to me to say that one belt does work if you can get enough tension on it and get the oil pump high enough to ensure the belt contacts with as muchof the pulley as possible.

Hope that helps?

 

[farmer.palmer]

@farmer.palmer there should only be one belt.
I have the same unit with only 2 owners before me and there has been no modification to the machine.
What I have found is that I need a short V-belt and make sure that it aligns perfect with the 3 wheels.
Next is to ensure that that you get as much angle on the wheel for the pump (get it as high up as possible) and move the motor as close as possible to the wheel for the oil pump.
If you do not do this the V-belt will glide when you use the hydraulic and putting pressure on it. The it get V-belt get hot and you loos power in the hydraulic.

Thanks for the reply. I sent you a reply via private message also to say I got this sorted by using two v-belts one on top of the other.
Thanks again.

 

[sLarsen]

Interesting.
Would you mind sharing the size of the v-belt you are using ?
I will give it a go also to see if I get a "new" machine
Regards
Steen

 

[farmer.palmer]

Happy to but it'll have to wait for a few weeks as I am away from the machine at the moment.
Cheers

 

[farmer.palmer]

@sLarsen
Looking back at the belts I ordered I think they are the following;

The shorter belt between the engine pulley and the oil pump is a SPZ 975 which goes on first.

The longer belt (which sits above the SPZ 975 on the engine pulley and oil pump pulley) and then across to the gearbox input pulley is a B54.

The oil pump is able to move in two directions which allows both belts to be tensioned, to do so you need about five hands and some very small spanners and a lot of patience....

Hope that helps!