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MG Midget and Sprite Technical - frontline front suspension modification

In the January 2021 Mascot Mike Pearson described how he manufactured a new steel pivot pin. Using 3⁄4 inch bright bar for his worn frontline front suspension kit. My aluminum! pin is worn on the inside and corroded too. The hollow pivot pin can rattle and turn around the fixation bolt. Is there any objection to use the bolt inside the as a pivot pin and make new Delrin bushes?
Flip


Flip Brühl

Flip,
I wouldn't have a clue about your main question but IIRC my mate said the bushes were igus, if you measure them and have a look through the igus catalogue you may well find they're not expensive ready made and probably self lubricating material(?). I know igus will sell small quantities and are good to deal with as I got 5 bearings from them to improve the T9 quickshift gear lever(s) I had from a well known set of con-artists.

https://www.igus.co.uk/Contact/Sales/NL/energychains

HTH.

Nigel Atkins

I read that article and was surprised he used 3/4" mild steel bar as it's a poor choice when 20mm chromed ground bar is readily available and far more suited to the job. As he was machining new bushes anyway the difference in wall thickness would be minimal. He could also have added a small chamfer to the flanges and added a small section O ring to act as a seal, the tension in the O ring helping to push it against the sides of the bracket.

The tube is required and should be made slightly longer than the distance across the bush flanges so that when assembled and the bolt done up the tube is clamped but there's clearance to allow the arm to rotate.

What diameter is the aluminium tube? 20mm?
David Billington

I do not know the diameter. I hope to take the suspension apart next week.David will it make much difference Bright bar or chrome on Delrin?
Nice site Nigel with telephone numbers. They speak Dutch.

Flip
Flip Brühl

Flip,

With Delrin the chromed shaft should give a much longer life due to the higher surface hardness and finer surface finish compared to bright bar. A problem with bright bar is it may appear round and measure a constant diameter with a micrometer or calipers but not actually be round, due to the method of production it can be like a Reuleaux triangle https://en.wikipedia.org/wiki/Reuleaux_triangle . I've seen it bad enough on a few occasions to cause problems holding the bar by certain methods, when chucked successfully a fine cut on the outer surface revealed the material to be trilobal and that feature spiralled down the length of material.
David Billington

Thank you. interesting the Reuleaux triangle. It looks like the heart of a W*nkel engine.
Flip Brühl

This thread was discussed between 14/04/2021 and 17/04/2021

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