Fuch Polishing Using DC Motor: Help Needed
 

Gents

I think someone has already done this, but I can't find the thread. (Speak up if you have.)

I'm in the midst of redoing my Fuchs, then another set, and I owe a buddy a favor, so I'm going to redue his. (Thanks but I have enough buddies.)

I want to take the pictured DC motor, rescued years ago from a broken tread mill and put on the shelf because I might need it someday, and mount it on my bench and then mount wheels on the motor, turn them to sand and polish.

I need something to adapt the AC 120 power from the house to the motor and some device to then vary the speed.

I have no idea what I"m looking for here, ideas?

Also, anyone have some ideas on how to mount the wheel?

Thanks

Wellbornhttp://forums.pelicanparts.com/uploa...1199224595.jpg


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I think it's going to be more trouble than it's worth to try and rig/adapt that motor. Do you have a Northern or Grizzly tools near you? They sell low-to-mid grade quality commercial buffers for less than $400.

But, if you insist, the best way would be to set-up a belt drive system with reducing pulley's. That way you can adjust the speed by changing the pulley size and not have to worry about finding the proper motor controller:

http://www.johnownby.com/images/buffer.jpg

http://www.americanartifacts.com/smma/advert/ay298d.jpg

Danny Ocean,

Thanks and I think you're right on the money. Just buy the tool I need, but...

Yes, I could just spend money. But that defeats the purpose. The challenge is putting together a Rub Goldberg assortment of parts to achieve the goal.....

Anyone else?

Try this:

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I see an AC power cord lying on your bench next to the motor...did you try and plug that sucker directly into AC service? If not, you are going to need an AC to DC transformer, which can get pretty pricy, along with a DC motor controller, which usually can be bought as a single unit:
http://www.clarkerewinds.ie/dc.htm
Don't suppose you have the rest of the treadmill still? It would have had this in it.

If you did plug it directly into the wall, I would reconsider Danny Ocean's suggestion.

I have a lot of tools being a contractor, a woodworker and a metalworker. I wouldn't bother with that. PITA, sorry. But if you take the money and spend it on something appropriate, I think you will come out ahead in the long run.

PS: I have 3 beach grinders and they all do a dedicated task. I don't think any of them were purchased new. Most likely garage sale or similar. They just don't die.

Ok, Milt speaks. Time to go to the pocket book and spend some dough.

I'm going to go price some bench grinders, maybe even a lathe of some sorts....

Do you have a big diode? 40 A peak 15 A continuous?
 

See if anyone agrees with this analysis for a permanent magnet motor. What I remember....

From the nameplate

• hp=2 = 1500 Watts
  • @ 3350 torque = 3.14 ft-lbs
  • 0.174 ft-lbs/amp
• V*I = 2340 Watts so 840 is wasted in the series resistance
• The series resistance is 2.59 ohms (P / I^2 or 840 / 18^2)

At nameplate conditions

• Vres = 46.67
• Vmot = 83.33
• k = 0.0248 volts/rpm
• L is unknown (and has some influence)

With no mechanical load, no friction; a half wave rectified line voltage would be 161 / pi or 51 volts average so the speed would be 51/.0248 or 2060 rpm

Full wave rectified line voltage (4 diodes) would be 161*2 / pi or 102 volts average so the speed would be 51/.0248 or 4120 rpm

[That 15 amps is the startup current]

http://forums.pelicanparts.com/uploa...1199241464.jpg

Rick

Thanks for the analysis but HUH?

That's greek to me. Just tell me what to do, how to build it??

OMG, you're smart.

wj

Buy a variac and a bridge rectifier, or just go to an electrical supply house and buy the cheapest dc motor control they sell.

Watch out for two horsepower though. That's enough to rip your arm off and beat you with the bloody end!!

If I were you, I would use some variation of Zoanas's idea above. You are not going to be able to easily come up with a way to solidly mount a wheel to anything unless you have some serious equipment to build a hub. Maybe if you have an old Porsche hub/spindle, you could do it, but it sounds like you may not have any serious fab equipment available to you.

You could buy a cheap hand drill from Harbor Freight and cob up some kind of cradle for it out of wood then simply lower the car onto it (just enough weight to drive the tire/wheel with friction) to drive the tire/wheel on the car like Zoanas shows above. It looks like he simply used a rubber sanding drum holder that can be purchased at Harbor Freight for cheap also. The beauty of the cheap drill is that it will be variable speed and can be had for dirt cheap. The bearings in it wont like the side loading, but it should last plenty long enough do to a bunch of wheels.

Years ago I blocked/braced up the back of a 944, and let the car idle in gear to spin the back wheel.

Yep, and the wheel spun plenty fast. I only needed one hand free to hold the sanding material. I put the drill on it's back, supported by the adjustable handle on the ground. It tilted just enough to apply the friction to the bottom edge of the wheel. Worked like a charm.

You could even fab a heavy base for your DC motor, set it on the floor and run a pulley with a large belt around the wheel.

I dig the flops, Zoanas:cool:

I don't bother reading his posts. They're secondary.

Strangely hypnotic....

I used an AC motor and a frequency transformer.
With the transformer you can alter the frequency, in my case to 25hz which in Europe makes a motor turn at half speed.
I got the transformer used for about $100, it could easily be sold for that again.

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If you want to do your rims properly dont forget to clear reanodise them or they will be back to chipped and scratched condition very quickly. You just have to breathe on the rim and they will mark. This means you will have to use caustic soda (oven cleaner works) or get them professionally dipped to remove the old anodizing, I cant stress this enough. If you are going to paint them in black as per original may I suggest using VHT Satin Black Polyurethane paint as it looks fantastic and is very strong (chip resitant) however dont polish paint for 3 month - you can drive with them though.

That would be called a VFD here, variable frequency drive. And they are quite cheap now.

Thanks for the advice guys. Safe in Sweden, it's your thread that I was looking for... what more can you tell me about your set up?

I note that you just let the wheel sit on the wooden hub and spin it that way. More tips?

wj

What would you guys think of this?

Imagine if I bought a variable speed 8 inch bench grinder from Sears.

I could remove the dust/shrapnel safety cover, remove the grinder wheel, and mount a wooden hub on the now vertical shaft of the "grinder", then mount the grinder on a piece of board, then put the board in my vice.

Any idea what HP size motor I should get? If 2HP will rip my arm off and beat me with the bloody stump, will a 1HP motor be enough? I worry about the torque needed to move the weight of a wheel.

Wellborn

Then, after the project

Those are "safety" flops, dude. :)


I'm not sure whether to be insulted or not... ;)

Did you try a car battery with your treadmill motor? 12 volts should run it about 480 rpm no load with .8 ft-lbs of torque stalled.

The motor I got (used at a scrap yard) had a M8 hole in the axle, not sure if all motors have something like that.
I cut out the "hub" a little to big and bolted it down. Then I started it up and turned down the hub to a perfect fit, like on a wood lathe.

What ever you do, protect your lungs, my entire garage was covered in a very fine aluminum dust.

Thanks for the follow up Mr. Safe,
Rick, great idea on the battery.
Zonas, I hope you are getting a patent on those safety flip flops.

Thanks to all, couldn't do it without Pelican People.

Thinking of changing my signature to PCar People Tinker Cause It's Fun.

Here's the current status of the project:

I am going forward with the 2HP DC Motor. KB Electronics makes an "adapter" that I plug the DC motor into, then plug the adapter into the 120V outlet. This adapter has a variable speed control. I called KB Electronics, quized the tech rep, then found what I needed locally for about $130 shipped to my office. (I figure I'm 45 years old and I'll redue a set of Fuchs at least three more times in my lifetime. So, this makes for a good investment. Just practicing rationalizing the expense to my wife.)

I dropped off the DC motor and a Fuch with a friend/client of mine that is an aircraft machinist. (Never hurts to have one of these guys as a friend. It amazes me the things he and his bunch can do.) I went to his shop at lunch today and I was the center of attention. Five machinist gathered around and started giving ideas. Over lunch tomorrow they are going to machine me a hub for the motor that I can screw onto the motor axle and the slip the Fuch onto the hub. It'll all be held in place with some "pins."

I'm going to take a 2x8 and bolt it vertically to my bench. Then I'll bolt the DC motor to the 2x8.

Thanks for everyone's help and ideas. I'll take pictures once I have it all put together.

Wellborn

Love Live the Memory of Warren. He helped those he never met and will continue to inspire those who are lucky enough to share in the ownership of a Porsche.

Below is a description of the adapter I purchased from www.kbelectronics.com

I include this for historical reference of the BBS.

The Model KBMD-240D, also called Multi-Drive™, is a packaged SCR drive in a NEMA-1 enclosure. It utilizes the KBMM™ speed control for its electronics. The Multi-Drive™ is rugged and compact in size. It handles both 115 and 230VAC line inputs by setting the built-in Dual Voltage Switch. In addition, the single model can be used on a wide range of motor horsepower by inserting the appropriate Plug-in Horsepower Resistor®. The Auxiliary Heatsink (optional) increases the rating of the basic unit. An optional Forward-Brake-Reverse Switch Kit is also available.

sub'd

Is this what you are looking for? This motor was salvaged from a washing machine.

http://forums.pelicanparts.com/porsche-911-technical-forum/271973-new-way-refinish-wheels.html

This is what I did:

http://forums.pelicanparts.com/uploa...1199416526.jpg

I should add that I have a couple of spare motors I'm willing to let go.

Jeff,

This is what I want to do in concept. I just don't want to do it with the wheel attached to the car. First, it's 20 degrees in my garage. Second, I don't think its safe. Third, I don't want all that aluminum grit in the air to fall on my car's paint, near engine, near axle, etc.

Rick,

Yes. The battery worked perfectly. I used a 12V car battery to test the motor to make sure it worked. I'm looking for eternal power, batteries run out. And, I'm looking for a bit more RPM. In a pinch, for a short run of wheels it would make sense. I'm just looking for a permanent solution and this is a fun project along the lines of a rube goldberg type of thing.

wj

Jeff,

BTW, nice cradle you built for the motor. Do you have a picture of the end of the motor's axle and what you used to "power the wheel"?

wj

Doesn't anyone have access to a lathe?

Yea, an old brake lathe for turning drums works nice..

Its actually pretty safe. I used the front axle to spin the wheel. By the time I did this I had used Oven cleaner to get off the hard stuff and this was a way to make sure I had a uniform finish on the rim as I planned to paint the spokes. There is very little waste flying off the wheel in this process. Not like a buffing wheel. I know!

The temp in the garage doesn't really effect the process. I used to work out of a detached garage with one of those turbo kerosene heaters. My wife complained that I always smelled like fumes when I got in the house but it was worth hiding out for a while. ;)

Thanks, I used a discarded bicycle tire to grip the rim and zip ties to hold it on. If you go to my original thread there are a bunch of pictures.

Update:

The original DC motor I had planned to use will not work with the KB Electronics device I was advised to purchase by the tech department at KB Electronics.

I went to the distributor, Ohio Brake and Clutch in Sharon Center, OH, to exchange the KB device for another device. (I quickly identified myself as an amateur at electrical stuff and these people couldn't have been nicer and more helpful.) The new device was going to cost a fortune, more than $300, given the application. The owner said it would be easier to just "give" me a new DC motor. And that's what he did, right off the shelf. Yeah, it was used, but its better, cooler, bigger, lots more torque than my treadmill motor .... pics later.

I'm tired and have to hit the road for five days of travel. When I get back I'll pick up on the project and update everyone. Meanwhile I have clean three wheels and even started some sanding and polishing.

wj