Anyone know about tumble polishing? How about an 11 blade fan?

Zeke · 10-22-2006, 09:45 AM

A local well known 356 restorer wanted $125 to tumble polish an 11 blade fan with no yellow cadmium plating or reassembly of the pulley. That was extra, big time. What's involved here? How big of a machine? I had thought of an older electric cement mixer with the vanes removed. Any ideas? Do I line the mixer (assuming that woudld work at all) with a protective layer of carpet or rubber? Sources?

The restorer dude says the finish of the tumble process is unapproachable AFA originality. NO bling, not for everyone, I guess.

shbop · 10-22-2006, 09:53 AM

interested... I've thought about the same thing.

bkreigsr · 01:40 PM

sounds kind of scary to let the magnisium fan tumble around for how many hours (days?)
with what medium?
could produce an interesting finish.
keep us posted
Bill K

DarrylD · 10-22-2006, 11:30 AM

Probably a vibration pot in crushed walnut shells.

viejopatron · viejopatron's Garage

Tumble polishing is generally used on smaller parts, however I'm sure there's some shops out there with big drums.

Magnesium I'm not sure about. Never had it done. I do know the media has to be matched to the material and desired results. I've used it on stainless stampings that came out beautiful. I've also scrapped parts out that were tumpled with too much enthusiasm.

Try calling Ollies. Those guys work with mag parts quite a bit.

kycarguy 935 · 10-22-2006, 02:16 PM

I saw the big tumblers at the Street Rods Nationals. They had all sizes for any type of shop. The small ones started about $2,000.00 if I remember right. They used little cat food looking pellets in barrel and let the parts tumble for hours. You should be able to make one your self out of the old cement mixer. I would line the drum with some carpet or thicker plastic and try to find the pellets they use. They had different grades depending on what type of part or metal your working with.

Maybe check the part frequently until you have the recipe right. Maybe put an old part in the mix first. Goodluck and let us know how it goes.

Shuie · 02:45 PM

Using a tumbler to polish a fan would require no work at all. Tell him to get bent and ask someone that handloads their own ammo to do it for you. Seriously, you can buy a large primo vibrating shell case tumbler and polishing media for $125. Check eBay and Midway USA also.

MBruns · 10-22-2006, 02:49 PM

We have a tumbler at work that I can try a less than perfect 11 blade fan, we use all types of media, the usual finish looks like frosted glass (we use it mainly for deburring CNC parts) If you have ever seen the "jet coat" silver on headers before polishing that looks like the dullest grey laquer primer and they tumble that with a small ceramic BB size media and it looks like chrome. I will try it on Monday

Mike Bruns JBRacing.com

AvonGil · 10-22-2006, 03:16 PM

Media is expensive, and will cost more than $125. Especially if you purchase the solution. if you want to buy a vibratory tumbler, it will be big bucks for the size required, even used. You are better off having it done by someone who already has the equipment.

Green 912 · 05:26 PM

You can make your own vibratory polisher for cheap. Go to home Depot. Get a 5 gal plastic bucket with fully sealing lid, a 20 inch box fan, a 3/4 inch nut and bolt about 3 inches long and 2 extra nuts, 4 carriage bolts and nuts and 3 bungee cords. So far you are out $25 or so max. Take the fan apart remove the wiring and controls carefully, remove the fan blades and cut the motor mounting arms to the size of the bottom of the bucket. Drill and mount the motor to the bottom of the bucket with the shaft pointing down from the bottom of the bucket. Drill a hole in the side of the 3/4 bolt right at the base of the head that is a little larger than the fan shaft inches in dia. Stick it on the fan shaft and tighten the nut to pinch it in place. Tighten the hell out of it but don't bend the fan shaft. Use electric tape on the wiring to protect it and you. Make 3 holes in the ribs that are moulded in the sides just under the lid 120 deg from each other. Hang the bucket form something with the 3 bungee cords to the 3 holes. Now that you have a big polisher you need media.

Grangers sells a selection of pro media. Get some of the type that is used to debur. It will look like little triangles of hard plastic. You should also get some walnut shell based polishing media. Grangers or gun shops will have the polishing media. Play sand works too but is slow. Expect to pay another $25 or so for the deburing and polishing media. Deburing media is not expensive and lasts a long time.

Dump the media of choice and the degreased part in the bucket, Snap the lid on tight, hang and plug the sucker in. Tinker with the 3 speeds on the fan switch. You want the bucket to buzz and move about 1/4 fro side to side not jump around like a cat is stuck inside. The bigger the load the more speed the bigger the eccentric weight will be needed. Use the two extra 3/4 nuts locked against themselves to increase the eccentric weight is you are cleaning a big load.

The motor will last from 20 to 60 run hours before flying apart depending on the eccentric weight and parts loading. Just get another $12 box fan if it does.

BTW Never media clean a carb body. They will come out looking new but the media will get itself in all the little ports and passages and never come out. Purty paper weight.

acapella8 · acapella8's Garage

Subscribing.

Green -- do you have any pictures -- this is a great idea.

Would love to see pics of what others have done!

Feel free to post or email pics to acapella8@aol.com

Ducman · 10-26-2006, 05:07 AM

Quote:

Originally posted by Green 912
Dump the media of choice and the degreased part in the bucket, Snap the lid on tight, hang and plug the sucker in. Tinker with the 3 speeds on the fan switch. You want the bucket to buzz and move about 1/4 fro side to side not jump around like a cat is stuck inside. The bigger the load the more speed the bigger the eccentric weight will be needed. Use the two extra 3/4 nuts locked against themselves to increase the eccentric weight is you are cleaning a big load.

How long does a part take? I realize this is variable - but would a fan housing more likely take 1 hour or 10 hours?

Thanks,
Don

MBruns · 10-26-2006, 05:15 AM

I tumbled a fresh bead blasted fan for about an hour and it looks pretty nice, not polished by any means but cool. I will try a different media and take some pics

Mike Bruns

KFC911 · 10-26-2006, 05:27 AM

Milt, have you considered powder coating? I don't remember the exact price, but Al Reed did my fan, housing, and engine tin for around what you were quoted. How are you planning on retaining the polished look over time? Here's a pic at the top of this thread:

Gratuitous pics of Carrera heater backdate...

RickM · RickM's Garage

Quote:

Originally posted by milt
The restorer dude says the finish of the tumble process is unapproachable AFA originality.

The original finish on the fan is not tumbled, media blasted or polished looking. Straight from Porsche the fan has an uneven, unattractive finish.

Also, the Cad plated pulley hub is riveted onto the fan. Is he offereng to remove this and re-attach or protect it when tumbling?

KFC911 · 10-26-2006, 07:15 AM

Quote:

Originally posted by RickM
....Also, the Cad plated pulley hub is riveted onto the fan. Is he offereng to remove this and re-attach or protect it when tumbling?

Good point Rick, I was going to have my pully hub cad plated (along with a bunch of other stuff), but decided to leave it 'as is' and had it taped over for the powder coating. I too would be curious as to how folks do this...

RickM · RickM's Garage

Keith I ran into the same dilema when doing mine. I did the same and taped off before bead blasting.

To clarify on the original finish, not only did the Magnesium have an uneven finish but it appeared that the fan had a poorly applied yellowish varnish of some sort.

Zeke · 06:49 PM

I think I know what a new fan looks like. This is what I'm after, not bead blasted or powder coated. I think the re-riveting was included in the 125. Not sure.

jim72911t · 10-26-2006, 06:55 PM

$125 seems a bit steep, but in this case you are paying for his expertise and investment in quality equipment, rather than the process itself. He's most likely got a decent size quality polisher, and I doubt you can buy one on ebay for $125. (We have one at work that would be appropriately sized for an 11 blade fan, and it was a steal at $2K. Media extra.)

FWIW, tumbling/polishing takes some experimentation and patience to master. The size of the part, size of the media, lubrication/cleaning agent, duration, etc., all take time to figure out.

In your case, I'd probably just bite the bullet and pay the price, unless you can find someone who'll do it for less (and has experience with mag Porsche fans). Trying to build your own polisher (and master it) will likely be more of a PIA than it's worth.

Good Luck,
Jim

Zeke · 10-26-2006, 07:01 PM

Quote:

Originally posted by jim72911t
Trying to build your own polisher (and master it) will likely be more of a PIA than it's worth.

I'd have to agree with that.