Another Brushless CRT

First off, I'd like to thank the people of the forum for all of their knowledge.

I finished my brushless conversion of a Jammin CRT X-1. I am really pleased how it turned out. I dont see how someone would want to still run nitro after driving this truck.

I have only run it twice for about 5 minutes each, due to rain, but I am impressed with the speed, handling, and braking. I was worried that I would be dissapointed with the 8XL performance due to everyone talking so highly of the Neu & Lehner's, but it is fast enough until the Mamba Monster Max comes out, when I will try 6s if it is supported!:018:

Like I said, I have only run it for short periods of time, but the temps seem to be ok. The ESC is a little warmer than I would like, so I am planning on getting a fan, but the motor and batteries are only warm to the touch on 12/46 gearing.

I dont know what runtimes are yet, but based on the runs I did and what the batteries took back, I should be able to get a solid 20 minutes of hard driving.

The motor mount is from Mike, here at rc-monster. It is really heavy duty, however I needed to dremel the area where the shaft passes through in order to fit my pinion. This was one of the first CRT mounts. (I spoke with Mike and he is making adjustments to the future mounts) I like the fact that the mount replaces the stock front diff mount. The center diff bearing fits in there perfectly.

I used the following components:
Mamba Max ESC (disabled BEC)
Feigao 8XL motor
Custom battery boxes
RC-monster heatsink & motor mount
2x 4s 4000 maxamps packs in parallel
Kyosho 46t Nylon Spur with center diff flipped
6V BEC

Here is a link to my picture page: http://picasaweb.google.com/joeharri...rushlessCRTPro

Let me know what you think and if there is anything that I overlooked.

[jhautz]

Looks sweet. Nice job!!

Only thing I see that I would worry about is how close the pinion gear is to the lipo pack. A nose down landing and that front tab on the battery box could bend and let the lipo contact the pinion gear. A spinning pinion will make short work of the lipo. If you can extend the front side of that battery box so there is no gap in front of the pinion gear and the lipo would be protected from the pinion in a worst case scenario.

Sweet job. Looks like it nice clean layout.

I am a little worried about that too. I had originally intended to use gorilla maxx straps that hold the battery in lengthwise to prevent the baterry from moving forward, but I am having a hard time finding a set to use. I think I'll put a piece of foam up front for the time being.

[jhautz]

Can you just use a wider flap of metal on the front of the battery box so there is no gap there? At least you would have metal between the lipo and the pinion then. I think putting some padding on the front of the battery box is a good idea too. Thats the edge of the battery that takes the most abuse in my experience.

What I should have done is mounted the L angle more towards the center of the truck, but I didn't have the motor mount when I made the battery boxes. I should be able to move it over though. I just wish I could get some gorilla straps, because they worked really well when I mocked up the box. I only have one, so maybe I'll just put it on that battery for now and leave the other one the way it it until I find another set. I'll come up with something before I run it today!

On my CRT I used velcro on the bottom of the battery to hold it in to the piece of aluminum on the chassis and also used gorrilla straps. The Lipos do not move at all. It works very well. It's been run many times now with no problems. Here some pics in this thread http://www.rc-monster.com/forum/show...&highlight=crt

[zeropointbug]

That thing looks absolutely deadly... :017:

Just looking at it makes me think it will jump out and eat me alive with no regrets. :026:

[BrianG]

Good job on the buggy. I think you will be quite happy with it. The XL motors are still good motors to be sure - it's just that some people want high-end for more efficiency (cooler running). I still run a 10XL in my Revo and love it.

About the straps; I just use this stuff for all my batteries so far and it's worked great. It's just a continuous roll of velcro. If you attach a piece to each end of the tray, it'll help keep the tab from bending in all but the most severe crashes. Even then, it should work. It's not GorillaMaxx straps, but it's easy and cheap to replace.

Added video and data log to my page here: http://picasaweb.google.com/joeharri...rushlessCRTPro

That velcro looks like it would work. I'll try to get some. I am not 100% set on gorilla straps, it's just the only thing I've ever seen that would work.

I got some temps running today. My batteries, motor, and BEC were all at a cool 87 degrees. The ESC was getting into the 170's. I have ordered a fan already. It seems that the mamba max is the weakest link, but it was never designed for what I'm doing, so it's still pretty impressive.

The video really doesn't do it justice in my opinion. The grass was somewhat thick, but I was running it in some dirt later and it was way faster. Also, I dont know if the diffs and shocks are setup for brushless power. The rear end is squatting alot and causing the front wheels to unload. Anyone have any suggestions? Thicker center diff? Firmer rear springs? I never ran this truck before, so I could use suggestions.

Current setup:
Shocks (F/R) 50/40
Diffs (F/C/R) 7/10/3

I also added an eagletree graph from that run. Runtime looks like it's around 20 minutes.
The ESC was set for 20% punch control.

[zeropointbug]

Hey, nice results! I think you have to calibrate your eagle tree for a lower voltage, it shows you have a max voltage of 17.02 volts, you should only have a max of 16.8 volts when fully charged. No big deal though.

again, NICE truggy!

Nice CRT, I just finished a LSP and thicker oil in the center diff along with stiffer rear shock settings help these brushless truggies. The unloading of the front tires is an issue, and these changes help. The stock suspension setup of truggies is too soft for the added weight and torque that brushless setups enjoy. I use 7K/50K/5K in my diffs and it helps. I know this is thick stuff, like corn syrup, but it works. Watching the fronts turn into pizzas is only fun for a little while. Have fun with your CRT.

[neweuser]

I really like the CRT's for conversions, they always seem to come out so clean! Nice job.
In my maxx, i run 7k/30k/5k and seems to do very well, i get great diff action along with traction.

[jnev]

Awesome truggy!!! What speed do you reckon you reach with that set up.

I too, am a little worried about the pinion and battery... a little too close for my liking.

I am going to get some diff oil this week and try to get the traction issue sorted out. It definately needs thicker oil in the center. I will try somewhere around 30 and go up from there if it still needs thicker.

Also, I cant seem to find firmer springs for the CRT. I have the stock blue (firm) on there now and can find only soft or med. Should I just thicken the rear shock oil or will I need a firmer spring too? I have 50/40 (FR) in my shocks now, would 60 be ok in the rear? 50?