Maxit

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Bearing Modification with stock steel shaft

This is a bearing modification using the steel pin that comes with the Havoc Heli. Its a bit different from the Carbon Fiber (CF) shaft bearing modification that I've seen and tried.

My biggest problem with the other modification was drilling out the Heli Frame Beam for fit of these small bearings. It seemed to be very touchy drilling the diameter required to fit these bearings. And also it leaves a very thin wall once drilled too. And finding a CF shaft of right diameter or geting CF rod may not be available to others. Let alone sanding a CF shaft down to the right diameter. NOT ME!

OK nitty gritty time! First thing I suggest is to disassemble the Havoc Heli as far down to whats in Heli-1 photo. (see heli-1.jpg)

OK! Time for a cigerette! Smoke'em if you got'em! The hardest part to all this is getting the heli disassembled without busting something. Taking the spur gear off the shaft without bending the shaft. Definately nerve wracking. What I did was use an old set of calipers that could be locked almost tight on the shaft above the gear. Then laid the callipers over a vise allowing the rotor blades down in vise so could tap on shaft. And gently tapped with a very small hammer, did I mention gently? Carefully making sure I didnt hit shaft at angle or gear wasnt at an angle to calipers I used. Hit shaft dead on the end and drive shaft through gear gently. Sharp but light taps it will come off easily enough.

Then What I did was carefully file some of the upper bearing down so its closer to flush with the beam.(See Fig1-a.jpg) I left these stock bearings in the frame to help keep the alignment of the steal shaft when I epozy on the 1x3mm bearings on top/bottom and bond them to the framing.

The reason the top stock bearing needs filed is to keep the total height down so the main rotor spur gear catches the motors pinion gear correctly. I've noticed if spur gear is higher on pinion gear, you will get alot more vibrations. So a spur gear hitting the middle portion of the pinion gear would be about correct.

If you notice the spur gear hub is taller on one side of gear than the other. (see fig2-a.jpg) I wanted as much of this hub as possible to hold on knurled part of the shaft. So I took the spur gear off and reversed this spur gear (upside down). This would be putting the shorter side of this hub down towards bearing.

Once I had gear reversed and then making sure when doing so, I did not bend the shaft during all this, I trimmed the short side of the hub off. With a new fresh sharp exacto blade I carefully trimmed off what was the upper hub (shorter sided hub), now which is the lower hub. (see fig2-b.jpg) Remember putting spur gear back on shaft reveresed what hub is left goes towards rotor blades should be the larger of the two sides of hub.

Now some will say "well shaft is a smaller diameter than bearing". And yes it is so the next thing I did was when I put the Spur Gear back on, I pushed it up on shaft enough to just have a little of the knurled part of the shaft appearing just below the spur gear. This knurled part I pushed into the new bearing and will keep it tight. Just a little tap to set this knurled part into bearing. To much of this knurled part pushed in these little bearings might crack center carrier of bearing. NOT GOOD!

Once you have tapped the bearing on so its tight enough you may still have a little gap from spur gear to bearing. Push the spur gear down so there is NO gap between bearing and gear. The bearing is thus tight up against spur gear now. And spur Gear and bearing are now both locked on the knurled part of the shaft. (see fig2-c.jpg)

Ok next week I'll tell you rest! Ok just kidding!

If you noticed when pulling things apart there is an upper and lower washer from its original assembly. You wont need the upper washer or put it back on at all. It would add more height to spur gear and how it matches up the pinion gear. The upper new bearing will rest on the filed down old bearing. No washer needed. But the lower washer will go on very bottom to help seal the bearing from stuff getting into it. So its now time to put the shaft back into the frame. Check the spur gear and how it matches up with the pinion. Should be just about right in middle of pinion? Now is a good time to put some grease into new bearings. But caution, dont get grease on side of bearing at all or epoxy will not adhere to bearing sides. For a good grease I used an assembly lube for putting automotive engines together. It has the right consistancy and is high temp moly lube. Its not as sticky at most greases goes either. Good stuff! A little dab will do yah!

Just as a check to keep head straight. You have the spur gear on shaft. Then the new ball bearing tight up against spur gear. Place shaft into framing beam into old bearing. Down through bottom old bearing and place the lower new ball bearing on end. Now put one washer on. Now hopefully you will find the shaft just makes it out to the bottom bearing and washer. You dont need the orginal brass collar thats pressed fit so dont worry. The knurl in upper bearing holds it all together. You need just enough shaft to come through to hold washer in place. You may need to push shaft through upper bearing a little more so just a enough shaft holds this bottom washer in place. Mine came out just right. But not enough shaft to put this brass locking collar back on. If you can put it back on do so. It will hold it all together for next thing to do.

Once this is all assembled as shaft, spur gear, new bearings and the one washer on bottom goes. Just carefully apply epoxy on frame beam and up onto sides of bearings. Being very careful not to get epoxy up on spur gear or into bearings. Getting a little epozy up onto the bottom washer will hold washer in place as a dust cover for bearing. Using a toothpick to apply dabs of epoxy helps. (see fig1-b.jpg) Make sure you keep bearings tight against old bearing surfaces so epoxy doesnt get in there. Now put it aside till expoxy if fully cured. 24 hours.

The epoxy now simply creates new seat carriage for the new bearings and locks them onto the frame beam. Also should make beam a little stronger too. Not alot of epozy is needed. Just enough to cover beam slightly and up sides of bearings all the way around.

Final outcome (see heli-2.jpg)

Well thats about it. Just put whole thing back together now. I use scotch tape to put body back together. So I can easily pull body off at anytime for what ever other mod I come up with.

samcoinc

Thank you for this info.

I got my bearings from precisionheli.. Wow those are small. I was playing with one on the rotor shaft and promptly pushed the center out of the bearing. oops.

anyways i did mine a bit different as I didn't want to leave the original bushings in there. (and didn't think I would be able to put epoxy on the bearings without destroying them )

-first I disasembled the rotor pulling the main gear off the rotor shaft. I used a crescent wrench on the shaft similar to your caliper usage and tapped the gear off.
-Next I pulled the bushings out and found a 7/64 drill (.109) which is about .01 smaller than the 3mm bearings. By hand I drilled (by hand I mean I spun the drill with my fingers) the frame about 1mm deep both top and bottom. Then I use the shank of a .125 drill to flair out the holes a bit so the bearing would start in easier.
-Now I put the main gear back on the shaft upside down like you did but I didn't make it shorter. The bearing being pressed into the frame instead of on top like yours gives me the right hight without removing some from the gear.
-I used the 2 washers that where originally on the shaft top and bottom and pushed the copper ring back on.

All and all it went better than I thought it would.

The first time I flew it with the new bearings it actually spun left. I had to correct with right trim. first time ever

Thanks again for the pictures and write up.

sam