Changing the size of a pulley

[Crispin]

Ok, so this is not exactly LC related but there are some pretty informed folk here.

I bought a new "self-propelled" lawnmower because my old one ejected a bunch of parts. Springs, levers, some brackets etc. It also had much ductape holding it together.

So the new one, a 145CC petrol jobbie pushes itself along at a speed meant for a granny. I want quicker. So, the drive pulley is above the blades which goes via a v-belt to the rear "axle" through a gearbox.

I want to put a smaller pulley on the drive shaft to make it go quicker. Being the young sprightly chap that I am I don't mine doing a quick jog if it means getting it done quicker.

Halving the drive pulley size doubles the speed. Is there a sizing "step" so that I can get a standard belt to fit without needing a tensioner? Where does one buy pulley's from?


C

 

[Towpack]

There's various pulleys for sale on Ebay. http://www.ebay.co.uk/sch/i.html?_f...elt+pulleys.TRS0&_nkw=v+belt+pulleys&_sacat=0 There's also a selection of different belt sizes available so you may be able to get a new belt of the right size if you can't make the original one fit.

I wanted to replace some plastic pulleys on an exercise/weight machine with steel ones and got some from a local lifting supplies Co. but these were for cables and not V belts.

 

[Shayne]

If you get a link belt like this just for example http://www.ebay.co.uk/itm/like/2519...rlsatarget=pla-183556653906&adtype=pla&crdt=0 it might make it easier to find a pulley .

 

[Crispin]

Thanks for the links. The adjustable belt is cool. Can it handle speed?

Halving the drive pulley size doubles the speed. Is there a sizing "step" so that I can get a standard belt to fit without needing a tensioner? Where does one buy pulley's from?

I'm wrong of course - making the drive smaller will reduce the speed. Not sure how much space I have under the shroud to make a bigger one.

I was hoping to print one. I can print ABS plastic with a max width of around 150mm. The mower is made of so many cheap parts I would be surprised if the one under the shroud now is metal...
http://www.thingiverse.com/thing:1226143

 

[Shayne]

They are stronger than normal belts i would say you will find them running alternators or almost anything on fishing boats .

 

[Crispin]

Cool, will try one of them. I don't suppose the load is that high.

Now to take it all apart and change the pulley...

 

[Shayne]

I would bet £100 there is a link belt turning this when there's about 4 stone of queenies in it .

640 × 480 - findafishingboat.com

No i wouldn't that buggers hydraulic , insert laughing face edit only allows new smileys and i have no idea what any of them mean .

You get the idea though most run on link belts

 

[Crispin]

I really do not know what I am looking at.

 

[Shayne]

Basically that's a big steel barrel ran (usually) by an electric motor link belt and pulley . You chuck 3 or 4 stone of shellfish in and while spinning it filters out the small stuff . Just an example of how strong these belts are .

 

[Crispin]

pretty sure it'll be ok then cutting my English lawn

 

[StarCruiser]

Shayne is right. Link or 'Brammer' belts can transmit more load and they have the advantage that they can be threaded around shafts rather than dismantling if you can't get the belt around. Whether you would have the room or whether the link belt would bend tightly enough to go round the small pulley on the engine shaft is one for trial and error.

You may be better printing a pulley as it depends on the centre you need as to how it fixes on to the shaft.

 

[t1pper]

I use a company called Kramp for all this type of thing, have a look on their website.
Sounds a bit basic but could the engine rpm be raised a bit to get it moving along a bit quicker?

 

[Crispin]

I use a company called Kramp for all this type of thing, have a look on their website.
Sounds a bit basic but could the engine rpm be raised a bit to get it moving along a bit quicker?

I suppose that would also be an option.

Reading up on it my mower is 2800rpm. In the US the max RPM for a 21inch blade is 3200 to keep the tip speed legal (ergo - safe). If mine is only 19in then I could go at least that and still stay safe.

 

[StarCruiser]

Usual running speed for mower engines is 3000 Cris…this was usually tested with a very simple wire device working on the vibrations.

In other words a hundred rpm either way is probably not an issue.

What mower is it BTW?

 

[Crispin]

Usual running speed for mower engines is 3000 Cris…this was usually tested with a very simple wire device working on the vibrations.

In other words a hundred rpm either way is probably not an issue.

What mower is it BTW?

I'd like to think it's one of these


But it's really one of these
http://www.mountfieldlawnmowers.co....owers/sp535hw-53cm-self-propelled-lawnmower-1