JP Super push mower.

[charlie]

I have a JP Super push mower that has a problem with rear roller not turning. I suspect something has seized up or broken in the gearbox within central roller.
My question is, how do you get the mower apart??? The cross shafts are held in place by cotters, but these appear to be almost impossible to slacken off and remove. I have managed to remove one cotter sleeve on axle for rear roller but cannot remove cotter bolt. So far I have had no luck with any of the other cotters.

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[trusty220]

It looks like the side pieces are made from aluminium. Could you use heat to try to move them- aluminium expands more than steel- but the chances are that the electrolytic action between the two different metals has fused them together.

If heat doesn’t work I would try the brick acid soak for a few days. It should eat into the corrosion and hopefully free up the cotters in the frames with an added bonus that it will de-rust the steel parts as well. The only trouble is that I haven’t used acid on aluminium, so you may want to monitor it closely (and put it outside because it gives off Hydrogen Sulphide- bad eggs- which can be harmful). Make sure that you soak the parts in a dilute solution of bicarbonate of soda afterwards to neutralise the acid as well.

Don’t blame me if it all ends in tears!

[charlie]

That might help with the ones that do not move at all, but the one I have got sleeve out of, bolt is loose but will not come out, neiher will shaft.

[trusty220]

Have you tried a bigger hammer?

With the sleeve out it would be worth pouring some acid down the hole so that it soaks directly into the parts that need to be freed off. I’d still try to soak the rest as well, it can only be corrosion that is holding it.

Best of luck.

[wristpin]

WARNING!!!!
Much of the JP’s chassis is, I believe, alloy and brick acid will immediately fizz and start eating into it with quite a violent reaction.
I would suggest getting the area around the cotter good and hot with a hot air gun or very carefully with a blow torch. Then putting the nut back on the cotter and giving it a firm hit. The cotters are, I believe, a standard cycle pedal crank part so are cheap and expendable.
At the risk of forum disloyalty, there are a couple of JP experts on the Old Mower Club who have probably encountered the issue and may know the answer.

[charlie]

wristpin thanks for the advice, I will persevere with the heat option and penetrating fluid. I was thinking of trying the OLC as I am sure someone there will know.

[trusty220]

Let us know what you find out, Charlie.

It may help if you could post a photo of the underside of the frame to show the other end of the fixing that you’ve removed. If the thread is loose in the hole it’s more likely to be a two-piece collet with a bolt going through them to draw them together and clamp them on the shaft. A sharp tap on the thread (once you’ve protected it by winding the nut back on) should push the bolt out of the lower collet, with the added advantage that if I’m wrong (and Angus is right) it will do the same job!

[charlie]

The cotters are in blind holes, so can only come out the one way.

[charlie]

Just registered to use forum, now waiting approval.

[charlie]

Approved and question posted.

[trusty220]

I’ve been doing a little homework since this morning and it appears that the pin with the thread on is inserted into a blind hole in the casting, the shaft is then fed through it’s hole then a sleeve is put onto the threaded part of the pin and everything is drawn up tight with the nut.

You may have loosened the one that you’ve been working on sufficiently but you will have to do the same with all of the others to get the side plate to move enough to get the roller out. A shame that they are in blind holes and you can only get to one side.

[charlie]

Thanks that was what I was starting to think.

[Author]

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