Brushless Mayhem ST Conversion Completed (kinda long)
 

Hey all, here is my recently converted Mayhem ST.

I used to be a Nitro guy. I loved tuning engines for peak performance and spent countless hours prepping / maintaining my nitro truck to always run in top condition. Then came the release of the Mamba Max, and I decided to purchase a Factory Team T4 and the 5700kv setup for it, just to try it out. All of the sudden I found myself constantly driving my T4 and I basically forgot about my Nitro Truck. Can you blame me? Electric rules! Instantaneous torque, insanely fast speeds, no fuel to mix, no after run oil, no air filters to clean and oil, etc, etc… I was hooked. I can’t remember the last time I drove my Nitro Truck…

With all the fun I had with the 1/10th scale T4, I started to research brushless conversions for 1/8th scale vehicles. With the help of a friend, I managed to find my way to the RC-Monster forums and discovered a wealth of information to learn from. I spent a good 5-weeks doing nothing but educating myself on the ins and outs of 1/8th scale brushless conversions, everything from ESC’s, Motors, batteries, motor mounts, proper layout to emphasize good balance, etc, etc. Amazingly enough, everything thing I could have possibly wanted to know was found by using the Search tool within the RC-Monster forum. Of course, none of this good information would be available to search for unless you guys existed and conversed so much about it. So to all of you I say Thanks!

Why would someone want to spend upwards of $900 and countless hours to convert a Mayhem ST to brushless..?? I seem to be answering that question a lot these days. The answer is simply that I already owned a Mayhem ST and have spent considerable amount of time making it a great Truggy. Plus the added bonus of having many, many spare parts for the thing already in my possession..

So, here was my initial Nitro setup:
Mayhem ST Truggy (purchased off ebay about 9 months ago)
Extended Chassis w/ 5mm Shock Towers (Kevin @ KP Racing)
23mm Hex Conversion
Upgraded Chassis Stiffeners
Turmoil Pro Ackerman
MT sized wheels w/ Crimefighter Tires
Aluminum Diff Cups (front, rear, center)
JR9000T Servo
Spectrum Radio/Receiver

Specs of Brushless Setup:
Neu 1515 1y Motor (2200kv)
Quark 125b ESC
(2) 7.4v 8000mah Maxamp Lipo’s (initially using 4s, later going to 5s)
UBEC
Reversed Center Diff w/ 46t Kyosho Plastic Spur (perfect fit on aftermarket MaXimizer aluminum diff cup, does NOT fit stock cup or Nova RC without modification)
12t & 14t mod1 Pinions
Custom Motor Mount (yes it’s ugly and crazily long, but it works – first attempt)
Custom Battery Mounts/Supports

I basically started this project observing the 40,000 RPM limit for my chosen motor/battery combo. I wanted the versatility to run both 4s and eventually 5s with the most efficient motor I could get my hands on. After many hours of research and eventually reading this very informative post (http://forums.radiocontrolzone.com/s....php?t=225698), I chose the Neu 1515 1y (2200kv) motor. The ESC was an easy choice; everyone who owns the Quark 125b and has installed a heatsink/fan seems to love them. What really put me over the top on the motor/esc combination was RC-Monster Mike’s post on the Neu 1515 and Quark ESC (http://www.rc-monster.com/forum/show...ghlight=quark).

For the Quark, I purchased two CoolerMaster PC Northbridge chipset heatsinks, removed the 12v fans and mounted a pair of 5v Evercool 5k RPM (5 CFM) 40mm fans using the existing mounts on the heatsinks. I used thermal epoxy to permanently bond the heatsinks to the rear of the Quark.

The Neu 1515 motor is a tank, it weighs 12+ ounces and I was a little concerned about that much weight in the front of the truck. Initially I was going to mount the Quark in front of the center diff, but moved it to the top of the center diff for better weight distribution. If It didn’t require making the motor wires so long, I would have mounted it behind the center diff (rear of truck), but it wasn’t worth the effort.

When it was all said and done, the truck weighed in at 11 pounds. The stock RTR Mayhem ST weighs roughly 10 pounds with fuel. To accommodate the extra weight I went to extra firm springs and 50wt shock oil all around.


Problems I ran into and their fixes:

I initially had a problem with interference in my radio w/ the Quark Controller. I resolved this issue by moving the receiver as far as possible from the motor wires. I figured the Spectrum digital system would be less susceptible to interference, but that was not the case. The receiver is now mounted in the rear of the truck at the base of the wing mount and I get no interference.

I mounted the Neu 1515 motor with it lying on the motor mount. I read many posts on how to support the rear of the Neu motor because of its weight. I really didn’t want the added complexity of a sliding rear support, so I used a small piece of flat aluminum on my aluminum angle motor mount to support the motor. So, the motor basically lays flat on the bottom of the motor mount and slides left or right for easy pinion size adjustments. The only problem with this setup is that (if you look closely) the pinion is touching the spur a little on the high side, which probably isn’t best for the spur. I intend to make some aluminum center diff spacers to raise the entire center diff in the air to have the pinion contact the spur perfectly in the center.

I wish I would have wired the UBEC into the Deans connector on the Quark, instead of onto the deans on the battery ‘series’ splitter. I will have to fix this when I decide to run 5s lipo’s, because they will need to be wired in parallel. (using 2 MaxAmp’s 5s 4000mah packs)

I need to put a switch on the UBEC, so the connectors don’t throw sparks when I plug them in and the servo powers up and 5v fans start spinning. Also, it would be nice to be able to switch off the fans and servo without having to disconnect the battery. Minor oversight on my part.

I started out with a little velcro under the ESC to act as a cushion, but I kept breaking zip ties. I'm not sure if that was due to rough edges on the center diff top brace or because the ESC wasn't cushioned enough. As of now and in the picture above, I used a larger piece of foam under the ESC and smoothed over the somewhat rough edges on the underside of the center diff mount and haven't broken any zip ties.



So, how well does it run???

Well, using this SPEED calculator (Thanks BrianG!) and the following specs, I initially geared it to run @ 36mph for the track:

4.09 ratio diff’s
46t Spur
12t Pinion
Tire Diameter = 5.6” w/ .15” radius for ballooning
2200 kv motor
14.8v Lipo’s

After my first day at the track I was extremely pleased! I ran the truck for about an hour and a half straight and it was amazing. Instant torque, extremely fast but controllable, no cogging what-so-ever, very smooth and well balanced. The Quark hit a maximum of 120 degrees F and the motor hit a maximum of 125 F (ambient temp about 75 degrees). I’m confident I could gear this motor to run in the upper 40 mph’s without any problems, but that’s too fast for the track. I ended my day melting my spur when the pinion set screw came loose, next time I’ll throw some blue loc-tite on there. I can’t say enough good things about the Neu motors, tons of torque, ultra smooth with the Quark and extremely efficient and cool running. By the way – I covered the ventilation holes on the Neu with electric tape and was initially worried about heat issues – to my surprise it still ran extremely cool.

Until next time - Later,
Michael

Nice job!

you can even use a 40T pinion with the motorholder LOL

No, serious, cool conversion and it was nice reading the post.

Welcome to this forum. Nice to see how other people convert their cars, thanks for sharing.

I also did a conversion of a truggy with the motor pointed to the front.
here she is..

Those kyosho spurs are truely awesome!!

Thanks!

lol, yeah my motor mount is much too long. I do intend to fix that at some point. :005:

Your conversion looks very nice! I also worked with limited metal working tools, but your's looks much nicer. I'm hoping to get better with each truck that I do. I'm looking into a brushless MGT next.

welcome to the forums!

very nice conversion, this does not look your first attempt at it!:005:

Everything is so neat. I really like it a lot. How does it run?

Thanks for the comment. The pictures are deceiving, my motor bracket is a total hack job and my battery supports aren't mounted perfectly straight and the velcro strap blocks are not equal length... etc. I did what I could with a bench top vice, hack saw, dremel (w/ many many cutoff bits) and cordless drill w/ cheap bits. :-)

My dad is actually a part-time machinist / metal worker, with a CNC mill and a nice lathe - but he and the rest of my family live 2000 miles away. So, I'm stuck with what I have for a while.

It runs great! I couldn't be happier. The added weight is noticable, but it's manageable. I can't say enough good things about the Neu / Quark combo. However, I do welcome the release of the Mamba Monster Max!

Yeah, even the mamba-maxx would have been enough! LOL (controller that is) it's going strong on 4S lipo.

Interesting you brought that up. 2 days after I purchased the $280 quark, I was reading about the Mamba Max on 4s in a truggy. I may end up throwing my Mamba Max controller out of my T4 into this truggy and use the Quark in my future MGT conversion w/ a Neu Motor.

I'd have to dream up some interesting way to mount a 40mm or bigger fan above the Mamba Max blowing down onto it. I guess I could use some fuel tank standoff's and a larger center diff cover to mount a large fan above the ESC.. Hmmmmmm.....

It's so nice and small, it seems to stay relative cool on the bigger motors on 4S.

I remember reading that Glassdoctor was successfully running a Mamba Max in his truggy, but thought he was using a fan on the esc. I could be wrong. You would suggest not running it with a fan?

Lol, why again did I spend $280 on the Quark.... :-) Well, I guess I can run 5s or maybe 6s on the Quark. I do recall reading a couple of posts lately where people were having some problems w/ 6s and even 5s on the Quark.. But, I'll just have to find out how well it runs myself.

It would be wrong of me to advice you the mamba-maxx on 4S anyway. It's working.. but it's not the way it should go. With the quark comes warrantee on 4S, i don't know about the mamba..

Some have good luck with it on 4S though.

I have run with and without a fan on the Mamba. If your temps are this low with your current setup then I doubt you have to use a fan, but expect some higher temps without of course.

Funny thing is that I'm gettting higher temps with both the motor and the esc than some others with similar trucks. I think I run mine harder, or with a more traction or something... :D but it still works great even with higher temps. Still well within acceptable limits.

I used 1.25" alu 4/40 standoffs to mount a 40mm fan above my MMax on an earlier version of my ERevo. I simply drilled and taped a hole w/ 4/40 threads in the 40mm pattern in the esc mount, then just use 4/40 screws thru the fans into the standoffs. Really easy to do and covers the entire esc, snugly on the sides. The fan then blows down on the caps as well, which is a bonus.

http://img245.imageshack.us/img245/1...3013eq8.th.jpg

I've been working on cleaning the layout up (something you did very well, congrats) and the esc has moved and has a smaller 25mm fan which is working well.

Very nice job and its good to see and hear about your conversion. I am glad you are liking the Neu and it is staying so cool. I am sorry to hear about the spektrum rx still having int probs tho. I was thinking about going to one of these hoping I could move my rx around and rid some of the glitching I get at distance. Maybe won't work like I'd hope tho.
Lastly, what grade alu is the mount? No chance of it bending or flexing?

Awesome job and happy racing. Post a vid if you can!

I have to admit that whenever I do go to the track, I am very easy on my truck. I have to drive 30 minutes each way to the track and it kills me to no end when I break a major part and have to drive all the way home after only being there for 15 minutes.... and of course, the part I need is the one part that I left at home.

When I convert to using the Mamba Max, I'll definately run it with a fan. I think most of the reason why my temps are so low with my current setup is because I'm not doing too much braking. I mainly rely on the driveline resistance to slow the truck down on the short straight aways and slide it through the corners. I only really use the brakes hard through 3 corners on our track.

Do you use any drag brake or any timing advance on your mamba powered setup?