Brushless Truggy #2

[shark413]

I had converted a CEN Arena truggy to brushless awhile back. It was crazy fast but I was not happy with the brake modulation and battery perfomance. I sold that truggy and concentrated on converting my 1/8 buggy and CRT.5, which were lighter vehicles and would be easier to convert. I had such great success with those conversions, especially getting the mechanical brakes working, that I decided to convert another truggy. I had a second CEN truggy that was not being used. I stripped it down and started to figure out what I needed and where everything would go. First I needed to make a special motor mount that set the motor back so that it would clear the disc brakes. I could have used the combo RC-Monster mount I had with a spacer to move the motor back, but I decided to make a custom mount that was separate from the center diff mount. I then replaced the CEN center diff with a Kyosho diff. I added Kyosho bonded semi-metalic brake pads/rotors. I cut and formed the new motor mount and drilled all the holes I needed to mount it. Coming up next I will add the motor, ESC, carbon fiber batt tray and brake servo.

http://i142.photobucket.com/albums/r115/shark413/P1010054.jpg
Here is my previous brushless truggy, it used motor braking. I sold this one a while back.


http://i142.photobucket.com/albums/r115/shark413/01010042.jpg
Here is the aluminum bar I used to create the motor mount.


http://i142.photobucket.com/albums/r115/shark413/01010043.jpg
Here is the rough motor mount being test fitted. I needed to get it close to the diff so I could use small pinions, but it also had to clear the brake rotor.

http://i142.photobucket.com/albums/r115/shark413/01010056.jpg
Here is the mount and motor/pinion being test fitted.


http://i142.photobucket.com/albums/r115/shark413/01010072.jpg
Top view showing fit of motor, brakes and center diff. It is very important to keep everything parallel when using a separate motor mount, otherwise you will have gear mesh issues.

Motor = Neu 1515 1Y or Feigao 8XL
Battery = Maxamps 4s2p 6000mah
ESC = MM
Diffs = front/rear CEN diffs with cross pin mod
Center diff = Kyosho with plastic 46T spur
Battery tray = custom carbon fiber

[ElectricThunder]

That's a beefy mount. Shouldn't you attach the mount to the center diff housing some how to prevent the gear mesh from waning due to chassis flex?

How'd you cut the mount also? I'm needing something to do besides work over the summer, so maybe a conversion or new kit is on the list...:D

[shark413]

ElectricThunder, hi, yes normally you should try and use a motor mount that is phyiscally attached to the center diff mount. This will give you the strongest mounting and reduce any flex. But when you use the mechanical brakes the motor must be set back about 5mm to clear the brake rotor. You could use a spacer infront of the motor to move it back, but the mount must be machined to accept the brake parts. The combo mount I have (motor mount integrated with the diff mount) does not support mechanical brakes. So rather than buy a new commerical mount that has been mechined to accept brakes I just built my own motor mount and set it back 5mm to give me clearence. Eventually I will build a support bracket that bascially surrounds the motor (to keep the Feigao endbells from popping off) and it also makes the mount rock solid (no flex). I have been using this setup in all my conversions (buggy and E-Revo) and it works great. When I first started making these things it was all by hand, for example to make a slot, I would drill a series of holes then use a round file to complete the slot. A bandsaw and files took care of the basic shapes. As I got more into it I decided I needed better tools, so I purchased a bench drill press and small mini-mill. Now I can cut flats, slots, holes, reduce metal, etc.

[ElectricThunder]

Awesome stuff. I see what you mean about the brakes in the way. Keep me posted; this stuff is super cool.:D

[GTX]

Looks great, how do you like the LiPo in there?

[shark413]

Update:

Here is a test fitting of the carbon fiber battery tray. Eventually the tray will have two sets of straps and small aluminum side rails to keep the battery from hitting the center diff/spur. When it is all done it should weight about 3.5 ounces. The cool thing about the carbon fiber tray, other than it being real light, is it is very strong so it only takes two bolts to hold it in place. This allows me to drill several sets of holes, which gives me the ability to move the battery forward or backward to get the CG I need for the track conditions.

http://i142.photobucket.com/albums/r115/shark413/P1010010.jpg

http://i142.photobucket.com/albums/r115/shark413/01010049.jpg
Here is a similar tray in my buggy. This is what the finished version should look like.

[shark413]

Update #1
Girlfriend had to work Friday night so I had some extra time to work on the truggy. I made up servo mounts and a motor brace. I originally made motor braces to keep my Feigao endbells on. The Neu motors don't need them for that, but having the motor hanging by just two screws and putting a lot of leverage on the area were it mounts to the chassis concerned me. The brace really triangulates the brace and makes the mount rock solid. I also swapped out the 26/9 diff gears with 38/11 to give me a lower gear ratio. On the original Cen truggy the center diff mount has spacers to help it to clear the huge spur gear. On my conversion, since I was using a much smaller 46T spur, I just added spacers so the chassis braces would sit in there orignal positions.

http://i142.photobucket.com/albums/r115/shark413/Image1-1.jpg
The original CEN truggy had huge ring gears 26/9T (left) I swapped them out.

http://i142.photobucket.com/albums/r115/shark413/01050017.jpg
Here is the ferriswheel CEN spur next to the Kyosho 46T plastic spur.

http://i142.photobucket.com/albums/r115/shark413/01050031.jpg
Here are the center chassis brace spacers.

http://i142.photobucket.com/albums/r115/shark413/01050012.jpg
Motor brace

http://i142.photobucket.com/albums/r115/shark413/01050007.jpg
Brake and steering servos and mounts.


Update #2

Saturday night I put the finishing touches on the truggy. Finished the battery tray, rx mount, hooked up brake linkage, added the ESC, added UBEC, added antenna mount and put everything together.

http://i142.photobucket.com/albums/r115/shark413/DSC00563.jpg
Top view showing the finished truggy.

http://i142.photobucket.com/albums/r115/shark413/DSC00555.jpg
Shot with the body on.

Update #3
Sunday morning off to the track for some testing.

http://i142.photobucket.com/albums/r115/shark413/DSC00569.jpg
Cen brushless truggy next to my Kyosho ST-RR.

http://i142.photobucket.com/albums/r115/shark413/DSC00570.jpg

[shark413]

Bad news, I went to the local track and the truggy was running great. Low temps and faster than any other truggy out there. Then in this one tricky section (a big table top followed by a big double) I missed timed the jump and landed pretty hard. I was on the throttle because I was trying to raise the front end so I wouldn't lawndart the truck. The truggy started to make some bad sounds so I brought it in to take a look. After checking I discovered I had knocked two teeth off the spur, the hard landing with full throttle put a hugh stress on the drivetrain, so the weakest part had to give, which was the plastic spur gear. Bad landings are going to happen, so I was trying to figure out how to make the drivetrain more durable. I had two options, 1) I could go to all steel gears (hardened pinion and steel spur), this would prevent broken teeth but it transfer the stress somewhere else like the diff or motor. Option 2) I saw a hopup part from Tekno that allows you to attach a nitro clutch to an electric motor. A clutch has several advantages, it smooths out the brushless power delivery, which reduces wheel spin. It will give a little (slip) which will reduce drivetrain stress. I made a mock up of the Tekno clutch to see if I could get it to fit. After trial fitting it looks good, I will have to move the motor back 10mm or so, and raise the center diff slightly. I can easily raise the diff by moving the spacers from the top to the bottom and I can drill new motor mount holes and move the motor back.

http://i142.photobucket.com/albums/r115/shark413/DSC04061.jpg
I turned down a Traxxas Revo flywheel and put a bell on it. I then put it on the motor to see how everything would fit.

http://i142.photobucket.com/albums/r115/shark413/DSC04062.jpg
If I raise the center diff slightly the cutout in the mount will line up with the bell and give me a little more clearence. I will also countersink the screws.

http://i142.photobucket.com/albums/r115/shark413/DSC04042.jpg
Here is the section that caused the damage. The arrow on the left is where you are supposed to land. The arrow on the right is where I landed.

[shark413]

Ok after reading some posts related to the Tekno clutch I decided to pull the trigger and I ordered one on Monday. It arrived today and I spent most of the night fabricating a new motor mount. I started by raising the center diff to give me more room, I then mounted the motor, attached the Tekno clutch (currently I am using MIP shoes) with a traxxas 15T bell. I also had to move the brake servo slightly to clear the bell. I hooked everything up and ran it on the bench just to see if it worked. The clutch acts just like a nitro clutch. When I gave it throttle the motor would spin but there was a slight lag before the bell would move, then as the speed picked up the motor spun the bell/spur at full power. This is just what I was looking for. Tomorrow I will put some street tires on and give it run in the yard to see how it performs under a load. Hopefully the power will be close to what it was with a direct drive and the clutch will absorb some of the stress in the drivetrain and prevent stripped spur grears.

http://i142.photobucket.com/albums/r115/shark413/01010040.jpg
Here is the new motor mount next to a RC-Monster mount and my originally mount. The new mount has been extended to provide more support.

http://i142.photobucket.com/albums/r115/shark413/01010046.jpg
Here is the mount and Tekno clutch attached to the chassis.

[garchpaul]

That was the most informative post thank you for making it interesting...

[ElectricThunder]

Really cool. The clutch acts like a little slipper on electric trucks. Interesting thing to do; wonder how it affects torque and startup (I would imagine startup is better since the motor starts with no or very little load, and then the clutch engages an instant later). Probably a nice little current spike when that clutch engages to give you a kick in the pants.:D

[rhylsadar]

very nice conversion! :respect:

bye
rhylsadar

[shark413]

Hey thanks guys. I am a little concerned with the two shoe traxxas clutch not being able to handle the power of the Neu motor. I have run the two shoe clutch in my nitro Revo with no issues. When I had my big block Revo I actually installed a special (made for the Revo) 3 shoe 1/8 style clutch and it worked great. I will test out the two shoe, but I may go to a 3 shoe clutch for added durability and tunability (with a 3 shoe you can change out the springs to adjust the engagement point).

[chewie]

if i were you id try the shoes without springs. since you really have no need to idle. you just need some slippage. without springs it will preety much instantly grab yet still freespool no problem.

[aqwut]

nice dude, did you do all the machining urself... ? Looks great, love the beefy mount..

[shark413]

aqwut, yeah I have a small mini-mill so I can machine small parts pretty easily.

chewie, I will definetly try the shoes without the springs. I want the engagement to be as fast as possible. Just waiting for my 13T bell to arrive. I also have a M2C 3 shoe (aluminum) clutch coming which should be more robust (designed for 1/8 scale) and it is a direct fit on the Tekno clutch adapter.

Just one thing to remember here, the Tekno adpater is designed for Revo flywheel/bells which are not 1/8 scale size. They are much smaller, so I can't use any old 1/8 scale bell, I have to use a special one (like the M2C) or the stock Revo bell (two shoe).

[shark413]

aqwat, in the picture below you can see the difference in professional CNC machining (mount on the far left) and my amatuer machining (two mounts on the right). But hey it works.

http://i142.photobucket.com/albums/r115/shark413/01010040.jpg

[kufman]

Your amatuer machining looks a lot better than my hacksaw, file, and drill press machining. LOL You might want to recess those motor screws a little bit to keep them away from the flywheel.


EDIT:

I just read the rest of this thread, you already mentioned the motor screw thing, sorry.

[aqwut]

Yeah, that mount looks familiar.. that's one of RC-Monsters, Mike's designs... :) are you using that Taig mini mill or something from harborfreight.?.. I have a shoemaker mill.... a 12" drill press, and a cross-slide vice.. :) works for me though..

[shark413]

I have a Micromark version, I think they all come from the same factory in China. I guess that metal shop class I took paid off.

http://i142.photobucket.com/albums/r115/shark413/P1010001.jpg

http://i142.photobucket.com/albums/r115/shark413/battery.jpg
Here's a Jammin CRT.5 I converted. This thing is a rocket.

[Muck]

Nice Truggies.
I had problems with the plastic spurs too. On my 1/8 Jammin CRT the spurs would break teeth occasionally. Especially, during on power crashes. I think that the plastic just can't handle all of that tork of a truggy. I ended switching to hardened pinion and a wide losi spur gear. Have not had any problems with that combo.

[shark413]

Muck, yeah I have only had problems breaking teeth on my truggy. My brushless buggy seems to run fine. I think it is related to the extra weight and contact patch of the truggy putting a lot more stress on the drivetrain. Is that Losi wide spur gear something special or are all Losi spur gears wider than normal? The reason I am asking is because most steel spur gears are pretty narrow (to reduce weight) but a wider gear should wear better (more contact), so I would like the option of running a wider steel spur gear with an hardened pinion on my truggy.

[ta_man]

The extra wide spur gear is a Robinson Racing aftermarket product:

http://www.robinsonracing.com/catalog/8ight.html

[shark413]

Update:

My Flywheel arrived yesterday, so today I turned it down so it was even with the bell. This flywheel is the special NewEra flywheel made for the Revo.
A little background, I have the Tekno adpater that allows you to use a standard Revo flywheel/bell, which uses two shoes and is smaller than a 1/8 scale bell. I wanted to use a heavy duty 3 shoe fullsized 1/8 scale flywheel/bell which is taller and normally wouldn't fit (too long front to back). The flywheel I got is specially made to be much thinner and allows a full size 1/8 bell in the same space as the stock Revo flywheel/bell.

I hooked it up with alloy shoes with no springs (so it engages sooner) and hooked it up. I took it for a spin and the clutch works great, it spools up smoothly before it engages, but once it engages it is very strong. Unfortunetly it was a little too strong and the combination of sticky tires, super powerful motor, wornout diffs and 100% traction blew out the rear diff. The diffs on this project have a lot of milage on them and were in need of a rebuild anyway. I spent the remander of the afternoon rebuilding both diffs. I hooked everything back up and ran it on workbench and it seemed to be working perfectly (too dark to run on the street). Off to the track tomorrow to see how it performs in the dirt.

http://i142.photobucket.com/albums/r115/shark413/01040010.jpg
NewEra flywheel and full size 3 shoe 1/8 scale Ofna bell.

http://i142.photobucket.com/albums/r115/shark413/DSC04062.jpg
Stock Revo 2 shoe flywheel/bell.

[shark413]

Update:

Got out to the track this weekend and tested the brushless truggy out. The good news is that the clutch performed well. It really did smooth out the brutal power of the brushless motor and handling was much improved. The bad news was I stripped another plastic spur, so the clutch does not slip as much as I had hoped. This was actually a good thing, because I wanted to test a steel spur gear and I had a spare diff with a steel spur. I installed the steel spur and ran it that way for the rest of the day. There were no further gear breakage and the wear on the steel on steel gearing was minimal. I am still concerned with drivetrain stress, and I guess I will have to wait for the slipperential. For now I need to decide if I should stay with the clutch and it's smoother power delivery, or go with a hardened steel pinion and eliminate the clutch and it's complexity/maintenance. I guess I will run it with the clutch a little longer and then decide.

[chewie]

im sure the heat of the clutch didnt help the spur at all..

i dont get how your stripping spurs. all the truggys that race here that are electric are doing fine. maybe let off when you land

[shark413]

chewie, I never thought about heat from the clutch. I don't think there was enough to actually melt the plastic spur, but may be enough to soften it. The first time was definetly driver error, I was full throttle and pancaked hard. The second time, it was a routine jump, I accelerated up to the jump, got in the air, hit the brakes to nose down slightly, then landed it on the downslope, thats as easy a landing as you can have. The only bad was I must have had some throttle going, because since the truggy uses a clutch, it would freewheel with no power and there is no way the gear would break if it was freewheeling. I ran my brushless 1/8 buggy all day using a plastic spur and I took some insane jumps with it and had no problems at all. I have actually run the buggy for about 3 months without any gear stripping problems. And it is direct drive (pinion directly to spur). I still think the extra bulk (weight) and larger tire patch (bigger/wider tires = more traction) contributes to the problem. I also might have a front CEN diff that is causing some problems, it seems to be catching (bad gear mesh) so I am going to replaced both diffs with new Kyosho diffs. I am going to use a steel spur but I am worried the stress that broke the teeth will now be transfered somewhere else, like the diffs or worse the motor (crack a magnet).

[chewie]

ive seen spurs melt on savages.. due to too much clutch slippage..

not to mention your running a bit more power than a nitro so im sure clutch heat did soften the plastic what about trying a vented clutchbell


if you use a steel spur you should be fine. are your diff bearings ok??? if they are bad your diff will wobble and change mesh. thats one thing to look at.

[shark413]

Chewie, yeah the bell is vented. I am going to stick with the steel gears and clutch for now. The diffs are definitely causing issues, the oringinal CEN diffs I am using had some crazy gearing (26/9T) and required a 66T spur. Since I was using the 46T plastic Kyosho spur the CEN diff ratios were too high. So I took some Kyosho ring gears I had from a buggy (43/13t) and mated them to the CEN diffs to lower the gear ratio. I would have liked to completely replace the CEN diffs but I had to keep the CEN internals because they use these really long outdrives and have a special pin that only works with the CEN spider gears. Anyways, the combination of CEN internal gears and the Kyosho ring/pinion is causing some meshing issues. I tried shimming them and they felt good, but I think I will just go with 100% Kyohso diffs using XRAY extended outdrives, which are compatible with the Kyosho diffs.