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Old 12-16-2008, 07:41 PM   #1
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Default 1/8TH brushless conversion build #2

I'm cutting and pasting from my post at londonrc.com just looking for a bigger feedback.


build #1- Ofna 9.5 with novak hv system and 4.5 turn motor.

the ofna was a long test of brushless feasability in a 1/8th scale buggy. It worked, and it was very fast. the biggest limitation was the drivetrain gearing. it was overgeared due to gearing limitations and I compensated for that with an extra fan. overall the brushless ofna was an A main contender. considering it started its life as an entry level rtr kit it was a huge success.

build #2 - xray xb8r

converting an entry level kit with spacers and bits of hacked up aluminum is not hard. The xray deserves better. So I'm stepping up my game for this one. I'm building new center diff mounts out of 6mm aluminum. one of the diff mounts will incorporate the motor mount so there is zero flex between the pinion and spur gears.

attached are some pictures. converted ofna pics with the 14.8volt 6300mah pack and the start of the x-ray build (nitro junk removed and cut radio tray).
Attached Thumbnails
1/8TH brushless conversion build #2-ofnaxray.jpg   1/8TH brushless conversion build #2-ofna.jpg   1/8TH brushless conversion build #2-x-ray.jpg  
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Old 12-16-2008, 07:49 PM   #2
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got the diff/motor mount parts cut, tapped and installed.

the radio plate is installed, but its ugly. unfortunetly because of all the elctronics I need the big ugly plate just to have somewhere to put it all. I layed out where I'm planning to put the electronics in the attached pictures.

the bec circuit and transponder aren't in the picture. the transponder is going over the servo.

I built a bec but it runs pretty hot with that digital servo, I'll probably purchase one thats a bit more efficent later. so I'm tempted to leave it out untill everything is closer to completion.
Attached Thumbnails
1/8TH brushless conversion build #2-precut.jpg   1/8TH brushless conversion build #2-newparts.jpg   1/8TH brushless conversion build #2-uglytray.jpg   1/8TH brushless conversion build #2-elec1.jpg   1/8TH brushless conversion build #2-elec2.jpg  

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Old 12-16-2008, 07:54 PM   #3
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ok, the center diff gear. basically I put the gear against a bench grinder while holding the bearings with the old diff supports. this ensures it stays round as it grinds the teeth down. I don't have any technique for measuring this, I just grind it down a bit at a time untill the edge of the teeth snap into a 66 tooth e-maxx spurgear with the center removed.

this technique is brutally effective and eliminates the need for any sophistocated measurements while making a complete unit that has consistant mesh with the motor pinion. infact the mesh is more consistant than when the e-maxx spur is installed in an e-maxx(oridginal).

anyways, once the fit is made, pop off the new spur and drill 2-4 holes in the x-ray diff gear to bolt the 2 pieces together. I used 3. those metal spurs are hard stuff and difficult to drill, even with a drill press and a good bit. pop the new spur back on and use the diff gear as a template to drill 3 holes in the new spur. the e-maxx spur never stripped on the ofna BL but its enevitable that someday a stone is going to do enough damage that it will. so I repeated the last step on 2 more e-maxx spurs as "spare parts". I tapped the holes in the diff gear and the new spur just to eliminate as much slop as I could and put it together with 3 short 3mm socket head screws and red lock-tite.

I'm doing it this way because, plastic 66 tooth e-maxx spurs are durable, cheap and easy to get. so are small 32 pitch pinions. the 66 tooth spur is also bigger than the typical stock 1/8th buggies spur and helps bring the gear ratio to a more suitable range.


and heres the pics.
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1/8TH brushless conversion build #2-spur1.jpg   1/8TH brushless conversion build #2-spur2.jpg  
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Old 12-19-2008, 07:45 PM   #4
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Progress slowed a bit. I wasn't happy with how far apart the new diff supports were in the stock locations. Because these pieces are thinner than the stock plastic ones the bearings were not being supported very well. I went back and put blocks on the bottom to move them in closer together. I'm happy with it now but it was a pain in the butt.

I had to redo the ugly tray to fit the new support positions. Its not a tray anymore, the new piece is smaller and not ugly.

Mounted the electronics and wired them in. Taped in a battery temporarilly to check if everything is working. Everything is OK. I bolted my home made BEC to the chassis behind the motor. I did a test to see how hot it would get. Turning the wheels left and right repeatedly I was able to get it up to 50+ degrees C. I don't think it will be able to handle the rigors of summer racing but it will do for now.

Ok, the quick release battery tray will be next. I'll probably be busy with that for a few days. Its just one of those pain in the butt projects but it will be worth it. I'll post again when its done.

Pics of the completed buggy minus battery tray. You might not be able to see but theres an aluminum antenna/ reciever holder. It has a set screw that locks the antenna in place. Above it is another block that has a set screw that holds the lipo cut-off LED.
Attached Thumbnails
1/8TH brushless conversion build #2-im000636.jpg   1/8TH brushless conversion build #2-im000637.jpg  
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