Cart Springs

[Adrian Southgate]

There are slipper pads on the ends of the leaves of spring 2 and spring 3, round plastic/nylon. Can't find a replacement part source on ebay or 'the usual suspects' websites. One of my multileaf springs has no pad left, just the remains in the hole in the spring. Anyone else found this issue, found a replacement part or do I have to buy the stuff to make some?

[Steve Kerswell]

I got hold of some teflon strips. Worked well but soon wore away. How thick are the washers?  Lots of nylon washer stuff on the net, think my stuff came R.S. not the car lot the engineering lot :-)

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[Adrian Southgate]

50mm diameter, circular, not sure of original thickness but the ones I have got left are worn down to 2mm thick at best.

I've ordered some poly resin, make a mould and make my own in 70 shore poly.

[Big Vern]

Do you have a picture?

[Adrian Southgate]

I can go and get one. Poly liquids arrive tomorrow so I'll know if it works or not by Sunday.

If there's a demand I'll make more. Mould should be easy enough to make as it's just two concentric circles, on at 50mm and on is about 14mm.

[Adrian Southgate]

Item on the right is the offending slipper bush. Centre spigot is 12.5mm outer diameter is 51mm and its about 2mm thick although I think this has been worn by the rust on the spring surface. There are four of these in a three leaf spring, one on each end of the lower leaves. I guess they are there to stop the leaves rattling. The springs have been split and the clamps that hold each end have the other thing in the picture. There is one on the front of the smallest leaf which holds all three leaves and one on the back of the middle one which holds two leaves. Two per spring and made from the same material. Might have to make a mould from plasticine if I am going to reproduce those too.

[James Doulton]

A mould for the one on the right looks to be easy enough to make out of plasticine, just pouring the poly liquid in to the required depth. The one on the left looks like it will need a two part mould and that will be a lot more difficult. A colleague has had some success by freezing the plasticine between short bouts of carving, in order to keep the plasticine rigid enough to make a two part mould. Even then, I don't think that the moulds survive to make a second one.

When I made a mould (a single part one) I used silicone rubber that I got from Alec Tiranti, which is a company that does lots of moulding supplies for artists.

You could also make a two piece mould out of glassfibre, as you probably have some hanging around. To make the first piece if the mould, you embed the item in plasticine up to the join line and then make the mould. Then when it is cured, you remove the plasticine, turn the item and mould over and make the second part to fit. When you make the original plasticine former for the first part then make sure that the join line is wavy or includes lumps or dips to align the two parts.

[Adrian Southgate]

I'll probably try with a flat item first, made the mould from recycled plastic using a hinge hole cutter 35mm in diameter then a 12.5 bit into the centre, much more awkward than it sounds with a dodgy shoulder and a hand held drill. Just looking for something to mix goo in and i'm away. using it in the back porch as it's supposed to be at room temperature and it's chilly out in the garage.

Long term I'd use a two part silicon block moulded as you described with the glass fibre which is the way to go anyway as I need to recast the 1/43rd scale leggie in resin to finish detailing. Stuff i've seen on you tube indicates using a vacumn jar to make sure I don't get any bubbles in the poly.... must have one of those somewhere... NOT

[Adrian Southgate]

Fluids mixed and i've poured four pads, two with 13mm bobbins and two with 12.5mm... not that i expect the mould to be that accurate due to the way it was made. Both bottles said 'shake before mixing' which is the last thing I wanted to do however most of the visible air bubbles came out as I was stirring the colour in. I've used black as it's 'common' and hopefully shiny so i'll see any surface defects. So now i'm waiting.... oh and this stuff would appear to be odourless lads so brownie points there if you have to work indoors...

[Adrian Southgate]

It's supposed to be a 60 minute demould.... 20 minutes gone...

[Adrian Southgate]

Times up... i'm off to extract some bits of poly...

[Adrian Southgate]

Observation and conclusions;- 

I drilled the mould deeper than required as I suspected there would be some sinkage in the compound and didnt want them too thin to use. They have a definte curve on the top surface.

First one out was a 13mm and it wasn't great due to defects in the mould surface, it gripped the mould and split between the noggin and the base plate, maybe I pulled too hard.. 

Second one out was a little better but still a slight split on one side.

Third one was off centre although it didn't look it while I was drilling the mould, better structure though and most definitely in one bit.

Last one is spot on, I'll try my springs with this smaller diameter and see what happens. I think they are going to shear off where the lump sticks up as they are only 70 shore and still 'soft' poly. Production versions will be have to be retooled and made from 85 shore which is pretty near solid. I can use number 4 on the right to make a mould which can be cleaned up and possibly enlarged in diameter.

Conclusion. - You can cast poly in the kitchen and it doesn't smell awful. It does need the air removing somehow as I do have some small bubbles present. 70 is too soft for this application however it will find uses elsewhere. I'm going to use 70 to do my leaves just to see what happens when they are stressed under load. (and I've already got it and need to reassemble the springs).

From left moulds 2,3 and 4 turned out. You can't see the split in number 2 but its there.

[Adrian Southgate]

Just been and pushed number 4 into the hole in the spring and it's a good fit. The locating pin is short by about 1mm so I can make it a bit deeper and flatter without any problem.