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qkingston

cleaning up the trailing arms

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So can anyone recommend the best way to clean up the alloy cast rear training arms on 4A? I imagine normal grit blasting is no good

Thanks

David

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David,

I suppose it depends on what you are trying to clean off. Mine had been undersealed and needed a soak with white spirit. Then a long blast with water from a Karcher high pressure rotating tip nozzle, the standard pressure nozzle would not shift it. I used water because it would not damage or remove material from the arms.

Alan

 

 

 

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ok thank, alloy wheel cleaner sounds like a good idea after an initial karcher blast!

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Glass bead blasting is best for aluminium parts.

Cheers

Graeme

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I had mine powder coated ... that was 15+ years ago and still looking good!

I'm pretty sure they were shot blasted before coating...no sign of rust but I can see how this could happen as Roger says.

Tim

 

 

DSCF0360.JPG

DSCF0367.JPG

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Soda blasting should be gentle on the aluminium, Scottblast in Greenock do soda blasting. I have seen poorly applied powder coating start to peel off on the edges.

               Cheers Richard

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Cleaned mine with Gunk/hot water and then used a brass wire rotary brush on a drill. They came up nice and clean after which I painted them with Silver POR 15 but you could use clear if you wanted.

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I've been told not to powder coat them because this can make it difficult the realise cracks.

And if you ever wanted to weld anythink that has been powder coated you think twice about it.

So I cleaned them with a Karcher and did nothing else.

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9 hours ago, qkingston said:

So can anyone recommend the best way to clean up the alloy cast rear training arms on 4A? I imagine normal grit blasting is no good

Thanks

David

Hi David,

           if you have look inside you may well find that it is full (ish) of white corrosion products. It would be nice to have this removed. But it will come back.

When I had my TA's off a couple of years ago I had the insides sloshed in Alocrom 1200 ( I worked on aircraft) https://www.lasaero.com/products/article/A00FWS9N9

This will stop corrosion in its tracks.  Rather pricey for home use. But there are companies around that do it through the back door. 

Mine were done at a place in Uxbridge Hillingdon for £30/pair.

Don;t powder coat the outside - as [er Marco's comments.

 

Roger

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10 hours ago, qkingston said:

So can anyone recommend the best way to clean up the alloy cast rear training arms on 4A? I imagine normal grit blasting is no good

Thanks

David

David,

I've had mine blasted in the past, but stressed "gentle" material be used and can't remember if it was soda or walnut shells or similar. I was pleased with the results and then just sprayed them inside and out with silver cellulose when it was more readily available. 

Whenever you clean them of, by whatever method, give them a close inspection for cracks. A particular point of interest should be the machined face where the hub flange is bolted towards the bottom stud.

Also check that all studs are secure. I have drilled mine out and fitted 5/16" UNC Helicoils and then fixed the hubs with cap head screws instead of studs.

Dave McD

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These are actually pretty robust items.  No need to avoid real (sand) blasting.  The aluminum used in the casting was not chosen for cosmetic appearance, though.

These were just blasted, epoxy primed, and painted.

Ed

SDC11569a.JPG

 

 

 

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I used a pressure washer inside and out then used Deoxidene to kill any corrosion followed by Alocrom1200. And got an alloy wheel finisher to give them a grit blast and powder coat them. Finished up with copious amounts of Astrolan before bunging the bungs in! 

As ed says they are pretty robust items, the only place I could see as a possible failure point is where telescopic shocks would attach, if the fillet radii are damaged. I think best left with the original lever arms.

I did take a peek inside with a borescope before I started and considering their age and location and lack of bungs were remarkably clean inside.

BTW we do use ‘shot’ of various grades on (high strength) alloy structures to improve the fatigue strength.

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Regarding checking for damage these were scrap! (Looks like a UJ had let go) also other cracks.

Stuart.

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2 hours ago, stillp said:

Interesting! What had the spring been sitting on Stuart?

Pete

Probably nothing! Though from other evidence on the car this came from it had definitely been raced as there was evidence it had been fitted with Aeroscreens at sometime.

Stuart.

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Blend out the crack on the web say 20:1. The crack on where the drive shaft passes through either weld it or make it into a slot and polish the edges. Tidy up the edges  blend that ‘scollop’ on the top, send it to Roger for NDT and it’s good to go.:P

Edited by DaveN
Spellin’

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10 hours ago, DaveN said:

Blend out the crack on the web say 20:1. The crack on where the drive shaft passes through either weld it or make it into a slot and polish the edges. Tidy up the edges  blend that ‘scollop’ on the top, send it to Roger for NDT and it’s good to go.:P

Long since in the scrap bin!

Stuart.

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Probably beyond JB Weld Roger, excellent as that product is, but I had a substantial crack repaired on a trailing arm 21 years ago and it is still going strong. I wanted to keep the old arm since it had been helicoiled for the hub attachment studs. I don't think any of the parts in Stuart's pics would have ben beyond a competent specialist Aluminium welder. 

Tim

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7 minutes ago, tim hunt said:

Probably beyond JB Weld Roger, excellent as that product is, but I had a substantial crack repaired on a trailing arm 21 years ago and it is still going strong. I wanted to keep the old arm since it had been helicoiled for the hub attachment studs. I don't think any of the parts in Stuart's pics would have ben beyond a competent specialist Aluminium welder. 

Tim

The arms were also peppered with corrosion as well and as I had a pair of good ones in stock then it was only sensible to skip them, The other one was just as bad anyway as the bracket for the brake pipe was missing!.

Stuart.

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