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Old Apr 15, 2012, 01:56 PM
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scatsob's Avatar
United States, NC, Jacksonville
Joined Apr 2006
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Idea
Motor shaft replacement, custom shafts, and bearing replacement service

So I have been re-shafting quite a few motors recently for various reasons and am just curious if there would be enough interest to start a service. Most of time I have been replacing a shaft that is too short and I wanted to maximize the bite on the adaptor. I can also install bearings from Boca if anyone desired to upgrade or just needed new bearings. Shaft material I have been using and is easy to work with is O1 tool steel. I is a little oversized so I grind it down by hand to fit snugly in the bearings of the particular motor I am re-shafting. I can do 3mm, 3.17mm, 4mm, 5mm, 6mm, and 8mm shafts. All I would need to know is how far you need the shaft to extend. Since I mainly do this for EDF use I do not cut C-clip slots, nor do I have the ability to do so. If the shaft needing replacement is for an endbell propeller mount motor that normally uses a C-clip, a Collar would have to be used. Priceing below.

$11.30 shipped back for 3mm, 3.17mm and 4mm shafts
$13.30 shipped back for 5mm and 6mm shafts
$15.30 shipped back for 8mm shafts

$1 per bearing installed plus the cost of the bearing.

If this is inappropriate to post here, then delete mods. I am not trying to start a business; I just like tinkering and want to help out people with shaft issues they don't want to rectify themselves.
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Old Apr 15, 2012, 08:40 PM
Jack
USA, ME, Ellsworth
Joined May 2008
17,222 Posts
I do all those kinds of things for myself now but others might be interested. You should be able to do the snap ring grooves and grub screw flats yourself, here is how I (a stubborn old ex-machinist who can do a lot of things) do it:

http://www.rcgroups.com/forums/showthread.php?t=1240725

You wrote:

"..If it is a little oversized so I grind it down by hand to fit snugly in the bearings..."

That will scare off most or all of your business. I can guarantee it will scare off all of the machinists!

O-1 (I know that material well) is slightly oversized and will not normally be consistent or accurately enough in size from one batch to another.

I buy shafts that are hardened and ground to size to be a no play sliding or light press fit into the inner bearing races. You cannot hand grind the O.D. of a shaft and keep the diameter within the range of tolerances that these shafts should have. These shafts really need to be made to a tolerance of about -0.0000/+0.0002 to 0.0005 to fit the bearings right.

The right sized shafts are widely available, I usually buy shafts that are a little too long and make them shorter. When I can't find shafts long enough I buy metric and inch sized (for 1/8" shafts High Speed Steel drill blanks and those are sized to need only cutting to length. And I add features like snap ring grooves and grub screw flats where they are needed.

Fitting prop savers is another service that you could offer, that is a natural adjunct to fitting shafts:

http://www.rcgroups.com/forums/showthread.php?t=1419378

Good luck with it! .

Jack
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Old Apr 15, 2012, 10:27 PM
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scatsob's Avatar
United States, NC, Jacksonville
Joined Apr 2006
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Wow, thank you for that link to the bit shank seller. Yeah, I know I will scare off the machinists. I don't have any readily at my disposal for things like this that’s why I started doing it myself. My first was a 6" long 6mm shaft for a contra motor. It was oversized and would not fit through the bearings and the only thing I could think to do was chuck it in a drill and sand it down. It worked great for me, although not precise.

Question. Are those drill blanks exact? If I buy an 8mm blank is it exactly 8mm? The shaft I origonally got from scorpion measures 7.98mm and I don't think 8mm would fit.
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Old Apr 16, 2012, 08:12 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by scatsob View Post
Wow, thank you for that link to the bit shank seller. Yeah, I know I will scare off the machinists. I don't have any readily at my disposal for things like this that’s why I started doing it myself. My first was a 6" long 6mm shaft for a contra motor. It was oversized and would not fit through the bearings and the only thing I could think to do was chuck it in a drill and sand it down. It worked great for me, although not precise.

Question. Are those drill blanks exact? If I buy an 8mm blank is it exactly 8mm? The shaft I origonally got from scorpion measures 7.98mm and I don't think 8mm would fit.
Here is a good choice for an 8mm shaft:

http://www.reidsupply.com/sku/MMB-97/

The link for the spec sheet is not bringing up a ISO 9001 type +/- spec and I can't seem to find one there. The size is listed to five places in inches (0.31496) so that gives you some feel for the precision but it is not the info a machinist would want to have or know.

I don't know why I can't find the specs there but here is another link that does have specs for typical drill blanks:

http://www1.mscdirect.com/cgi/NNSRIT...PMPXNO=1680237

In our complicated inch/metric metalworking world it gets weird. That is a 8mm drill blank and they have listed the tolerances as decimal fractions of an inch. The tolerance for the shaft there is:

Blank Diameter Tolerance (Decimal Inch) +0.0000 to -0.0005

and the blanks from Reid Tool would be the same. The shaft will not be undersized and it will be no more that five ten-thousandths over sized. And that, along with the tolerances typical for bearing races, will give you the no play sliding fit to light press fit I mentioned.

If you order the Reid Tool free catalog you may find the specs listed there.

When I have ordered from Reid tool I did it by phone to place a small order (a few drill blanks). By doing that the lady that took the order set me up for a mail shipment (cheaper) instead of the (more expensive) UPS ground shipment that you get when you order online with the automated system.

The drill blanks will be lacquered or have an invisible preservative coating on them when you get them. It is best to use like 400 or 600 grit emery cloth, dip them in light oil, spin them up in a drill motor (or use your lathe if you are a lucky dog) and take them down to bare and bright metal. Clean all traces of abrasive off, give them a light coat of oil, and either slide them or press them into place. The fit will be so good that is is almost orgasmic....

Jack
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Old Jul 06, 2012, 02:18 PM
Eagle, ID
Joined Nov 2005
66 Posts
Hi:

I have an Align 600XL motor that needs the bearings replaced. I cannot open the motor. Can you help me with this? Or, would you rather replace the bearings. The bearing are available from several sources.
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Old Jul 07, 2012, 05:49 PM
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scatsob's Avatar
United States, NC, Jacksonville
Joined Apr 2006
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I found this thread over on HeliFreak on replacing bearings on that motor.

http://www.helifreak.com/showthread....=600xl+bearing
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Old Jul 22, 2012, 05:26 PM
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United States, AK, McKinley Park
Joined Dec 2010
195 Posts
Hi, The service is a good idea for those without a lot of time.

I've got a little time and am willing to change my own bearings, so I'm wondering what type and spec of bearings are the best quality. Specifically for this motor

http://www.headsuprc.com/servlet/the...ushless/Detail

I'm using 4 of them for a quadcopter and need something with low friction, durable and probably shielded or sealed (given all the dust that can blow around on takeoff and landing).

Any suggestions for ceramic, teflon, shielded, sealed, etc...? Also an economical place to buy them?

I also have some other motors with a 4 mm shaft I would like to upgrade as well.
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Old Jul 24, 2012, 11:04 AM
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United States, FL, Pompano Beach
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http://www.bocabearings.com/ has any quality you want.
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Old Jul 25, 2012, 03:14 AM
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United States, AK, McKinley Park
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Quote:
Originally Posted by zeroback View Post
http://www.bocabearings.com/ has any quality you want.
Wow, I had no idea they made full ceramic bearings at $100 a pop. That site has almost too many choices. I guess I'd go with what's affordable.
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Old Jul 25, 2012, 06:10 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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I found Boca's prices, in the cases of some bearings, to be inexplicably high. I have have good luck with bearing from these places:

http://www.avidrc.com/product/1/bearings/
http://www.rcbearings.com/
http://www.vxb.com/ballbearings.html

I also have bought bearings on eBay, for a 8mm x 4mm x 2.5mm bearing search for the string "bearing 8 4 2.5" and you'll get hundreds of hits. You have to study the details a little to sort out the ones you want.

Bearings are generally rated by their ABEC numbers with ABEC-1 being ordinary quality bearings and ABEC-7 being high quality. But that value is not often stated and there is also a lot of humbuggery going on whereas ratings (not marked on the bearing itself, maybe marked on the package) are misused.

So I just look for ordinary quality, maybe ABEC-3 or so, all steel bearings. I occasionally find bearings from Japan or European source at ordinary bearing prices and will choose those over no-name Chinese bearings. I buy what looks like a go0od balance between cost and quality.

Bear in mind, installed bearings are very vulnerable to damage from impacts and dirt. In the long run properly lubricated and frequently replaced cheap bearings may be better than that maybe dirty, maybe damaged, maybe poorly lubricated, ceramic bearings that you are reluctant to replace because they cost so much.

And finally, when I buy bearings I usually look for the "RS" or rubber seal series bearings because the seals on those seal better and are less prone to being damaged or lost in use.

Rubber seals have more drag than metal seals so you do have to give up about 3 one millionths of a Watt of power for each bearing. The green seals are the prettiest, red seals are faster, any color will work...

And every bearing I have ever bought was not well lubricated on receipt. So I put them in a little bag of Mobil One 10W-40 motor oil and pull a vacuum on the bag with my Mity-Vac brake bleeder to vacate all air and replace it with oil. Then I drain them, blot off the excess, and install them.

Lube can create more drag, that dead silent, perfectly smooth running, slightly over lubricated bearing is quietly consuming another 1 millionth of a Watt of so of your precious power. When you go to the National Championship go a little easier on the lube.

If anyone tells you that an over lubricated bearing is prone to damage from being hammered by the wave effects of an excess of oil, snort derisively and walk away.

If anyone says that a poorly lubricated bearing is prone to damage and likely to have a shorter service life, nod knowingly and agree with them.

Jack
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Old Jul 27, 2012, 10:40 AM
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I'm experimenting with $10.00 ceramic bearings from Boca. The fellow at the counter said to wash the lube out as it collects dirt and run them dry. I have these installed on the HK2730 motors and so far so good. Using the fancy bearings as an experiment (plus there just up the street) as I have always received good service from 95% of the bearings that I have cleaned and lubed on a regular basis. I'd like to see if they are worth it in the long run on small motors before laying out the big bucks for larger motors. And if nothing else it's a novelty to have a custom wound motor with lube free ceramic bearings, sounds good anyway.
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Old Jul 27, 2012, 10:52 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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It does sound good. And I'm sure that there is a competitive flying venue where the small increases in power that might result will be taken with joy.

It would be interesting to do 10 or 15 second full throttle runups with a data logger before and after installing the different types of bearings and maybe even in the different states of lubrication. But I don't think I have the time or even accurate enough measuring equipment.

Jack
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Old Jul 31, 2012, 10:27 PM
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Question. Are those drill blanks exact? If I buy an 8mm blank is it exactly 8mm? The shaft I originally got from scorpion measures 7.98mm and I don't think 8mm would fit
These links have shafts of that nature.
https://sdp-si.com/eStore/

https://sdp-si.com/eStore/

All sorts of goodies there
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Old Aug 01, 2012, 02:56 AM
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Thanks!! That's good info, I ordered some $1 rubber sealed bearings from Avid RC, we'll see how they do!
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Old Aug 01, 2012, 07:19 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Quote:
Originally Posted by zeroback View Post
Question. Are those drill blanks exact? If I buy an 8mm blank is it exactly 8mm? The shaft I originally got from scorpion measures 7.98mm and I don't think 8mm would fit
These links have shafts of that nature.
https://sdp-si.com/eStore/

https://sdp-si.com/eStore/

All sorts of goodies there
If it is actually exactly 8mm that would be about the perfect size for a light press fit in the bearing race.

If you measure with a caliper you won't have enough precision to really tell what the size is. If you use a tenths reading imperial or metric micrometer it will most likely read right on the money.

In the world of drilling holes with pointed drills, it is impossible to get a hole that is not slightly larger than the drill. So the blanks are generally just a tiny bit smaller than the called size.

The drill blanks are generally coated to prevent corrosion when you get them. If you check them up in an electric drill, put some light oil on a piece of 400 or 600 grit emery cloth, and polish off the coating before you try to press the lightly oiled shaft into the race, you'll not have any problems with drill blanks fitting.

"..All sorts of goodies there..."

It is enough to make an inveterate tinkerer want to cry with joy, isn't it?

They use that stupid frames html so I cannot post a link to the individual pages but if you go to the pages for precision shafts and then the pages for precision drill rods and compare the tolerances you'll see the tolerances for under and over sizing and the drill rod is normally much more precise than shafting.

Jack
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Last edited by jackerbes; Aug 01, 2012 at 07:25 AM.
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