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Hi and thanks for looking

I have an older Ligier Matra f1 chassis and was wondering what the best method would be to restore the chassis to as close to original as possible. The under-chassis has some road rash from some usage, but no too bad. I'd like to sand it down, but don't want to mess it up by using the wrong grits of sand paper. If anyone here has done this before, any help would be grateful as I'd like to bring this car back to it's original glory.

I'd need to see how bad it is to be 100% on what grit you should start with - it needs to be rough enough to take enough material off to get to the bottom of the deepest scratch in a decent time... you could do it with 1200 grit, but it might take forever. I'm not sure how thick the chassis is, but you might have to live with some battle scars to avoid undue thinning.

In general, I'd start with 400 grit, depending on how bad the chassis is, then work up through the grades - using more grades (e.g. 600, 800, 1000, 1200, 1500, 2000 & 2500) will be more expensive in terms of paper, but will be quicker than doing it with fewer grades. TBH I've stopped at 1200 or 2000 & then gone on to polishing, but that isn't an original look - going on to 2500 should give a smooth but satin look.

Do it wet with plenty of slightly soapy water & don't expect it to be quick...

I'm not clear on whether the chassis plate is entirely flat or not - if it is, and you can actually hold on to it somehow, it might be possible to sand the whole thing at once (fix the paper down on a flat surface - a thick sheet of glass was the way I used to do bike cylinder heads, but for RC cars I used wet a bit of kitchen work surface & let suction hold the paper); if not, a small block of wood should help avoid rounding the edges.

Hi and good luck.
Alu is a poor metal.
It is fat
If you want to have it shiny, It doesn't heat. It must be cold. You have to polish it with very fine sand paper and really softy. You have to sand it on all the surface at same time.
good luck

Thanks

The chassis is flat and it's mostly scars from being so low to the Tarmac. I guess I'll do as you mentioned which makes sense. But I don't want to polish it, although I think it would look good.

here's what it looks like.... sorry for the lack of lighting... The chassis is not so bad, but I might as well take care of it while it's all apart...

What I usually do with aluminum chassis is to first use very fine sand paper (800 to 1200 grit) The aluminum is so soft that coarser sandpaper will make too much scratches.

To get back the semi-flat appearance, I finish off using " Steel Wool " This gives a nice finish that is quite close to the original.

If you want a more flat look, you can quickly dip the aluminum in Caustic Soda, but be very careful as the Caustic Soda will etch away the aluminum in very short time.
Remember, Caustic Soda does not remove any imperfections, so a good prep job is required for a good finish. I used Caustic Soda on the chassis of this XR311 . You can see that where there was residue from the servo tape, the caustic soda did nothing, leaving the alu as before.


Another route is to polish after steel wool, which will give a nice and shiny finish. I use Autosol for polishing.

-Lars

some great advice, thanks guys

Lars for your xr311,
Caustic soda ate the alu It had a chimic reaction very toxic
I made it on gas motor and the result is less than good. Some toxic gas are create and some parts of the aliage are disolved.
sometimes the chassis is anodized maybe is it on the gitane and the xr311. Be carefull
When we sand the anodized alu parts. They haven't any protection and are fast oxyded as your xr311 part.
be carefull

Lars,
On your picture I think that the anodization is gone

I don't think the vintage aluminum chassis from Tamiya are anodized.
But, I agree with the toxic fumes. Caustic Soda creates chloride gasses when in use, so be careful.

-Lars