Any experts on restoring these? I've got a 49D that has some lacquer or varnish that's been applied, making the finish dull and yellow. I'd like to know if that's common, and if it's advisable to use lacquer thinner to clean it off before polishing with a buffer.

Thanks in advance,

--anixi

I'd strip the stuff off and polish it to a mirror or satin finish, which ever you prefer.. IIRC, it was noted by people in this forum that some older Strionglight cranks did not even have anodizing and were just bare posihed or matte aluminum alloy.
If you want to put on a protective finish, do not use clear varnish as it does yellow and break down quicklly in the elements. There are modern clear resin cotings you can use that will hold up much better and never yellow. Check out "Everbrite" resin coating. It's used by car and motocycle enthusiast to coat and protect polished aluminum wheels with good results.

Chombi

Thanks Chombi. I assume that lacquer thinner won't affect the finish on the aluminum.
--a

I dont think it would as it is not known as a corrosive.
Like they say, test in a small unconspicuous area before proceeding!

Chombi

But if it's long-dried varnish or even lacquer, lacquer thinner may not cut it. But I'd start there. Show us some pics when you get 'er all shiny.

Yes, please post pics. 49Ds were not anodized so whatever is on there isn't original. Once you have it removed, they're easy to fix up with files, sandpaper and steel wool. This week I filed the gouges out of a non drive side arm and sanded it smooth.

I second (or is it third?) the above recommendations. That's my favorite part about Stronglight 49d and 93 cranks, no anodizing. Try small, inconspicuous areas at first as some chemicals are enemies with aluminum alloy. I'm no chemist, so I can't say which, but we all know the deal about soaking in Simple Green, etc. Not good.

I've had good luck removing enamel paints from components with just a rag and some isopropyl rubbing alcohol (the stronger 91% stuff available at Walgreens, etc.). Not sure if that would apply to a varnish or clear coat, though.

You think I can polish these out?

I'm a fan of silicone buffing wheels for polishing aluminum cranks (and other alloy stuff). I use a jewelers "dremel-like" motor tool made by **** Frei (it's like the Foredom tool). The polishing wheels are the "Italian" type. They do a great job of polishing alloy cranks to a high degree of lustre.

realestvin7. Your cranks are certainly in sad shape, but you can bring them back. It will take some significant effort though. I'd start with a pneumatic dual action (DA) sander and some 80 grit, and work your way up to 600 plus grit paper on the flat areas. You CAN do this by hand, but it's a lot of work. After that, entertain the fluted and rounded edges with sandpapers BY HAND and then a final polish using buffing wheels. I'd suggest a dual end motorized buffing motor w/wheels set-up with a course to medium compound on one end and jewelers rouge on the other for final luster. You are going to lose some definition to the crank and thin them out somewhat in the process as you sand the base metal, but I don't think that it would be objectionable.

You MAY want to consider sourcing some replacement cranks in lieu of this repair effort, particularly if you do not have access to the needed machinery or have to pay to have the work accomplished.

I'm getting ready to polish out my 93's on my Super Tourer myself! Fortunately, mine are only slightly dull with minor scratching though.

On the subject brought up about clear coating after polish...I've contemplated CC on the entire crank set, but I'm concerned about the chain ring teeth area and the resultant interface of the chain rubbing / removing the coating as I'm sure it will. I guess one COULD mask off the teeth and leave them naked so to speak.

And for those contemplating the removal of ANY current coatings...it all depends on the nature of the coating proper. Some may have to move up to MEK or Acetone to dissolve whatever is on there. One may also find that abrasive removal (Scotch-Brite or sanding) is required. It all depends on whether the coating is an "epoxy" or enamel coating, plated or Anodized. Cabinet style Glass-Bead blasting is another option for coating removal as well.

Not a problem... I'd start with some 3M scotch-brite abrasive pads, maybe the burgundy coloured kind, they are like pot scrubbers on steroids and they've worked well for me. I've seen drill attachments that are made of the same stuff and they'd likely make quick work of those cranks and leave a nice brushed finish that should polish up nicely with finer grit abrasives and some polish towards the end.

I think I used windex to clean this crank with a scrubby and then I hit it with a buffing wheel in a drill and used some polish and it polished up to a mirror finish with very little work. The dustcap is still pooched though.


mystery bicycle by clasher, on Flickr

I could polish those to a shine you could shave in...

You guys are crazy. I've already decide to scrap them. The pictures don't show how far gone they are. Lol.

Are they cracked or bent ?

You could scrap them to me just for fun to see if I could make them look like these.

Goners.

Troof. Polish these turds...

A comparison.

Well, the pictured cranks are FUBAR, including cracks and delaminated/scalloped metal surfaces that compromize their
structural integrity....However, they stil could be polished up nice!

I plan on polishing the drive side. Wait to see what I have in store...

All you need are two ingredients once the clear coat is removed.

1) Mother's aluminum polish
2) Eldow grease

I wouldn't recommend trying to seal the finish with a clear coat (as previously done). A yearly re-polish is all that's needed to keep it looking like new as long as the bike is kept in an air-conditioned environment.

Well, went to the hardware store, the guy said even MEK won't touch hard/dried lacquer. Only stripper will work. Put the stripper on, left it for over 20 minutes and it didn't even begin to dissolve it at all!
Any ideas on what will dissolve hardened lacquer, only without ruining the finish? I want them left without any details ruined, of course!

How did you decide it was lacquer vs. epoxy, varnish, eurethane, etc. or some other coating?

Heat? A heat gun can soften or lift most cleat coatings and if you don't overdo it, won't hurt the aluminum alloy.

Also, acetone is routinely used to clean aluminum before painting, is a (strong) component of lacquer thiner, and evaporates before it would have lasting effects. So, it should be safe enough on the aluminum. It will soften any lacquer after a while. Don't use acetone with a heat gun! :-)

The person who gave it to me said that it was done decades ago with a rattle-can. No recollection of the exact stuff.

I did find "Aircraft Paint Remover" that's sold at O'Reilly's auto parts store. I'll get some and see what happens. But, before that, I'll see if I can steal some of the little lady's polish remover. I do also have a heat gun, which I'll use as a last resort. Some website out there recommended boiling the snot out of it to loosen it up. I'm not anxious to go that far.

Thanks for the suggestions all!

It's a bad idea to use aircraft paint remover on aluminum.

...and the paint "stripper" sold in most hardware stores is a mere shadow of its former self.