Another Moulded Wheel

Discussion on Design, Build and Mechanical Theory.

Another Moulded Wheel

Postby slurp on Mon Mar 31, 2014 8:06 am

MouldedTyreDefect.jpg
Glue Gun Moulded Wheel, RTV Rubber Tyre
MouldedTyreDefect.jpg (53.35 KiB) Viewed 1305 times


This wheel was manufactured with the glue gun moulding technique noted in the other thread. The tyre is cast in an open top mould using RTV Silicone Rubber with a black pigment.

The defects arise from a combination of problems, little too much activation agent setting the rubber too quickly and the viscosity not suiting the narrow tyre mould. This leads to the air pockets highlighted in the picture. The mould is to be amended to give a thicker tyre, that should allow the rubber to flow more easily. Unlike some of the other moulds shown on this site, I used an open top mould had this been sealed enough to inject it may not have had the same problems.

The moulded wheel is 7-8g, overall once the tyre is on this is 10g. With the thicker tyre I'm expecting the finial item to weigh-in about 12-14g which helps keep the wheel inertia down.

best regards,
Colin
slurp
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Re: Another Moulded Wheel

Postby slurp on Sun May 04, 2014 7:06 pm

assembledmould.jpg
Assembled Tyre Mould and Wheel
assembledmould.jpg (78.42 KiB) Viewed 1297 times
rubberflashing.jpg
Tyres with mould flashing
rubberflashing.jpg (94.87 KiB) Viewed 1297 times
timmedtyres.jpg
Trimmed Tyres
timmedtyres.jpg (96.59 KiB) Viewed 1297 times


This new mould was a whole lot more successful.

The outer ring is simply a tube cut to length and faced off to be square, the base has a step to locate the moulded wheels and the tube. The larger opening allowed the rubber to flow more readily - this is appoximately 3mm depth. A little less activation agent was added so setting took a little longer, this may have allowed the bubbles to rise out of the rubber too.

I've removed the overflow and trimmed off the flashing. Weight is as expected, approximately 14g. Pull test later to judge the tyre performance.

More detailed info to follow on the wiki.
slurp
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Location: Milton Keynes, UK


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