Wobbly Wheel Restoration

[weswigginton]

I've recently acquired the Al Murray '67 Brabham BT21-5, which was fully restored by Huffaker Race Engineering in 2016. I'm curious if anyone could provide expertise on how to properly refresh the Wobbly Wheels. I'm assuming they are magnesium? Is it as simple as media blast and paint? Or do they require special attention due to the fact they are magnesium? Additionally, the shoulder on one of the lug nut mounting perches is somewhat broken off. Is this a repairable situation? See attached photos.

Thank you

[tlracer]

If they're magnesium then having them chromated is the best base surface finish to prevent oxidation. In fact these look like they may have been chromated already, going by the dull grey surface.

Magnesium alloys - especially old ones - can be very porous and 'gas' badly with things like powdercoat because of the heating involved.

With the seat repair, a good wheel guy might be able to weld/recut. Alternatively the damaged area might be better machined to an inverse cone, then have either equal cones on the back of the nuts (either machined solid with the nut or as a separate washer.

Just my two penn'orth (as we say this side of the pond...)

[weswigginton]

Thanks for the feedback. Are you thinking the finished surface that I'm seeing on the wheel is the actual chromate material? Or is it a base coat that is then painted upon? Good idea on the inverse cone thought.

If they're magnesium then having them chromated is the best base surface finish to prevent oxidation. In fact these look like they may have been chromated already, going by the dull grey surface.

Magnesium alloys - especially old ones - can be very porous and 'gas' badly with things like powdercoat because of the heating involved.

With the seat repair, a good wheel guy might be able to weld/recut. Alternatively the damaged area might be better machined to an inverse cone, then have either equal cones on the back of the nuts (either machined solid with the nut or as a separate washer.

Just my two penn'orth (as we say this side of the pond...)

[tlracer]

Chromating gives a range of different colours, depending on the process used. Typically it is mid-to-dark grey, nearly black.

It's difficult to tell from a photo but the outer face looks like it could have been chromated. Could the lighter inside be a sealant coat that's been applied afterwards?

Chromate gives a good base for painting onto as it's a chemical conversion of the metal surface.

[macbt21]

I agree that they look recently treated with chromate or similar treatment. I recently had some wheels treated with DOW #7 and they look very similar. The treatment is very thin so spray painting would be a good idea. If you get them welded remember to get someone with magnesium experience. If the wheel starts burning it's finished. This is what DOW #7 looks like.

[weswigginton]

Thank you for feedback and images. I'm curious how you can tell that my wheels look recently treated? For me it simply appears as they have been painted. Can you refer me to who performed your Dow #7 treatment?

All the best.

I agree that they look recently treated with chromate or similar treatment. I recently had some wheels treated with DOW #7 and they look very similar. The treatment is very thin so spray painting would be a good idea. If you get them welded remember to get someone with magnesium experience. If the wheel starts burning it's finished. This is what DOW #7 looks like.

[tlracer]

Because chromate is a chemical process, it produces a very regular finish, even in corners and holes, where paint might tend to collect.

Although it's not easy to be 100% certain from a picture, chromate has a distinctive 'look' because of this.

[macbt21]

Thank you for feedback and images. I'm curious how you can tell that my wheels look recently treated? For me it simply appears as they have been painted. Can you refer me to who performed your Dow #7 treatment?

All the best.

From my minimal experience, this type of treated surfaces of magnesium are a chemical conversion and very thin unlike paint. Scratches and abrasions from normal use will show a white powdery corrosion and your wheels look to be very good. Also the white inside paint looks unscratched from tire changing. The wheels I show are in heavy duty plastic bags with desiccant packs to protect them from corrosion before painting. If you like the look of your wheels I would suggest occasionally wiping them down with GIBBS treatment. Visit their website to learn more. It is an excellent corrosion protection. I had my wheels sand blasted with new glass beads to remove the paint. New medium is important because you don't want to contaminate the magnesium. Also use clean gloves and don't touch the magnesium with your bare hands. Time the glass beading to be done very close to the treatment day.

I had my wheels done by PTI Industries in Enfield, CT because they were within 6 hours of my home and they did high quality MIL spec work and were ISO certified. They provided me with treatment documentation and packed each wheel individually in plastic bags with a desiccant pack. I think any company that does this type of treatment on aircraft parts will be OK.

[DanW]

If you are going to chromate treat your wheels yourself, make sure you read and follow the SDS available with any of these products. Most of the treatments are versions of hexavalent chromium aka chrome six, very poisionous. Proper PPE is a must plus careful disposal of residue.

[GreginCanada]

Rather than attempting to weld the broken away lug nut seating area . I would use a high quality , metal filled epoxy . Devcon etc. Less risk than welding. It looks like you still have at least 90% of the load bearing surface intact which should be plenty.

Greg

[Raleigh]

https://www.henkel-adhesives.com/vn/...esiumaero.html

[weswigginton]

Thank you Greg!! I will look into Devcon.

Rather than attempting to weld the broken away lug nut seating area . I would use a high quality , metal filled epoxy . Devcon etc. Less risk than welding. It looks like you still have at least 90% of the load bearing surface intact which should be plenty.

Greg