Brushless Truggy Part 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.


Here is my previous brushless truggy, it used motor braking. I sold this one a while back.



Here is the aluminum bar I used to create the motor mount.



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.


Here is the mount and motor/pinion being test fitted.



Top view showing fit of motor, brakes and center diff. It is extremely important to keep everything parallel when using a separate motor mount.

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

[suicideneil]

It must be nice having a vertical mill, I really need to get a cheap one sometime- so many ideas, so few resources.

Looks good so far, the seperate motor mount does make using mech brakes front & rear alot easier = options.

[Shark413]

It's a real cheap mini-mill, I got tired of drilling and hand filing. I spent more time working on the mill (getting it true) than on making parts. I have an RC-Monster motor mount that I could have used with a spacer to set the motor back, but it was an older model and wasn't machined for the brake parts. So I decided to make a simple mount from scratch. Eventually my setup will include a rear support for the motor so all the stress doesn't fall on just two endbell screws.


My Neu motor cost more than this mill.

[Shark413]

Update:

Here is a test fitting of the carbon fiber battery tray. Eventually the tray will have two sets of straps and a small aluminum brace to keep the battery from hitting the center diff/spur. When it is all done it should weight about 3.5 ounces.




Here is a similar tray in my buggy. This is what the finished version should look like.

[Shark413]

Ran, into my first major issue. The CEN TR uses 26T/9T front/rear diff gearing (2.888888) which is pretty high. The nitro CEN uses a 52T spur to make up for the high diff gearing but I am using a 46T plastic spur. Even with an 11T pinion I get a top speed of around 50mph, too high for what I need (track). I was going to pop in some spare Kyosho diffs I have, but I remembered that the CEN TR has really long outdrives and the Kyosho has shorter ones, using the Kyosho outdrives will cause the dogbones to pop out. So I guess I will try and mate the Kyosho ring gear and pinion to the CEN diff.

[jhautz]

Actually the CEN Matrix BUGGY uses 26/9 gears in the diffs. The truggy uses 38/11. Its still rather high for a truggy (actually very close to what most buggies use, 43/13) but not as bad as what you originally thought.

When I converted my CEN truggy I found the same thing. I started off with a very low KV motor to compensate for the tall gearing and 46T center gear. Eventually, I actually switched to the Hot Bodies 43/10 truggy dif ring and pinion to lower the ratio and allow the use of a 46T spur gear without a super small motor pinion. The HB ring gear and pinion fit the CEN difs with a little careful shimming to get the mesh right.


EDIT: What are you planning to use for chassis braces? The stock over the top braces dont look like they will work with your center dif arangement.

Here is a link to my CEN Matrix TR thread in case you are interested.
http://www.rc-monster.com/forum/show...ight=matrix+tr

[Shark413]

Hummm .. I have both (CEN buggy and truggy) and in my case the truggy has the 26/9T and the buggy has the 38/11T. Thats why the buggy uses a normal size spur and the truggy uses the ferriswheel spur. The teeth on the truggy ring gears are huge, probably why they could only fit 26 teeth on it. I have Kyosho ring/pinion gears and they fit on the CEN diff, so that may work (Kyosho ring/pinion with CEN diff). If that fails, I will stick the CEN buggy diffs in the truggy since the gearing is lower. And I am using a lower kv motor (Neu 1515 1Y). Regarding the brace, I saw someone else (may be you?) convert a CEN and they used spacers to match up the Kyosho diff mount to the CEN chassis brace. I have HB spiral pinions from another project, but the ring gears are gone (another project). Sounds like you have plenty of experience converting a CEN truggy, so keep the suggestions coming, while I am still in the planning/building stages.

[supralover72]

Very Nice dude!

[jhautz]

I'm not sure where you got your buggy and truggy from, but from the factory the Buggy comes with the 26/9 gears and the truggy comes with 38/11. Check your part numbers and manuals. The huge teeth you are talking about belong in the buggy and are mod1.5 pitch instead of the normal mod1 pitch gears.

Matrix Arena comes with MXS38 Steel Ring Bevel Gear-T38xM1
Matrix Buggy comes with MX040 Ring Bevel Gear d6(26T)

I have both as well and actually moved the CEN truggy difs (38/11) to the buggy and put the HB 43/10 gears in the truggy. That gives them both "normal" (or very close to it) gear ratios.

[Hakan_J]

Originally Posted by jhautz

I'm not sure where you got your buggy and truggy from, but from the factory the Buggy comes with the 26/9 gears and the truggy comes with 38/11. Check your part numbers and manuals. The huge teeth you are talking about belong in the buggy and are mod1.5 pitch instead of the normal mod1 pitch gears.

Matrix Arena comes with MXS38 Steel Ring Bevel Gear-T38xM1
Matrix Buggy comes with MX040 Ring Bevel Gear d6(26T)

I have both as well and actually moved the CEN truggy difs (38/11) to the buggy and put the HB 43/10 gears in the truggy. That gives them both "normal" (or very close to it) gear ratios.

I have noticed that the Factory Pro version of the buggy has different Bevel gears than the RTR version!

Edit:
Could be the source for this confusion....

[Shark413]

Update:
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, 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.


The original CEN truggy had huge ring gears 26/9T (left) I swapped them out.


Here is the ferriswheel CEN spur next to the Kyosho 46T plastic spur.


Here are the center chassis brace spacers.


Motor brace


Brake and steering servos and mounts.

[Shark413]

Update:

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.


Top view showing the finished truggy.


Shot with the body on.

[Shark413]

Update:

Sunday morning off to the track for some testing.


Cen brushless truggy next to my Kyosho ST-RR.

[jhautz]

Looks great!. Let us know how it runs. I love mine.

[Shark413]

Well bad news regarding the track test. My local track has a big table top followed by a big double jump. Normally you land on the back side of the table top and then take the double jump. The truggy was running great for 4 or 5 laps, but then I gave it a little too much throttle and I pancaked my landing into the face of the double jump. The truggy started to make some bad sounds so I came in to take a look. What I found was that the hard landing and subsequent stress it put on the drivetrain had knocked two teeth off the plastic spur. So now I am looking at ways to prevent this from happening, obviously landing under full throttle is bad but it happens once in a while, what I want to do is make the drivetrain a little more durable. I figured I have two options, 1) use a hardened pinion and steel spur. This would be the easiest solution since I wouldn't have to modify anything, but the drawback is drivetrain stress will still be passed to the other parts, so instead of a spur stripping now a diff gear will break or something in the motor will give. Option 2) would be to add a clutch or slipper, right now I could get a Tekno clutch. This would provide some give (slip) and smooth out the power. The draw back is I would have to modify my current setup to make room for the clutch. A slipper differential would also be great but I have not seen one in production yet.

jhautz, sounds like you have a lot of experience with both items (clutch and steel gears) any suggestions?