another crt.5 brushless in progress

I found this forum just a few days ago when searching for information on converting my 1/8 cen matrix to brushless. I had also been keeping an eye out on ebay for a b44 or some other 4wd 1/10 sized off road brushless rc. Then I saw crt.5 mentioned on here and after reading a post or two I had to get one. Picked one up on ebay for $130 shipped w/ brushless motor mount, new tires and foams, and the small hi tech metal gear servo installed. It isn't the long chassis though but since the decent servo was included I went for it.

I want to stick with a123 batteries instead of lipo because I like to run non stop for a couple hours at a time when I go to the track. Time waiting for a battery to charge is time wasted. The key with a123 is having just two packs and the ease of charging a 3s pack in 15 minutes by hooking it up to any 12v supply capable of 10 amps. My charging setup for ac or dc is ugly and cost less than $30 but I guarantee nobody is getting more runtime than me per hour spent at the track :) And I've been a lot in the last few months to compare against nitro and other electric guys.

My goal is to have a quick crt.5 on 3s a123 that can run for close to 15 minutes of racing (or non stop practicing at the track if you wanna call it that). If I go to 4s or higher I need to get a 10amp charger which will run at least $125+. I'll use a mamba max but what motor would be good? I have a castle 4600 that runs really hot on my rustler and also have a used vxl on the way. I'd rather start with one of these motors before buying a medusa. Any suggestions on gearing and motor choices? I'll dig through the old posts now as well. Thanks guys.

[Arct1k]

Skip the castle motors too small for a 4wd CRT.5 - Go for a medusa 50mm - 3000kv.

Convert a computer PSU and have 20+ amps for $45

will 3s a123 at 9.9v and 2300 mah get close to 15 minutes? or would I need 4s? or even 2s2p 6.6v and 4600 which I can charge up without having to get a new charger?

I guess I need to really decide on batteries before buying a new medusa motor. Wouldn't I want a higher kv if I was going to use only 6.6v? What is the target rpm? 30,000 rpm? And what size pinion for speeds of around 40mph max on 2.2 tires?

I am leaning toward a 3s a123 setup for starters but would consider more cells. Have a look at the various options for battery position. Thoughts? Suggestions? Some would be much easier to fabricate a mount for than others, but all are possible I think.

link to pictures:

http://picasaweb.google.com/chadrebu...y=uJC2WRxigkY#


Chad

[MetalMan]

The 4s1p "brick in back" seems like it would be the most feasible. Honestly I wouldn't go with any less than 4s1p to achieve 15mins. Just make sure it's geared for no more than about 35mph, otherwise that 15mins. might be difficult to reach.

[BL_RV0]

I too like the 4s brick.

I took it to the track today and was quite impressed though I couldn't drive it for more than a couple packs. One of the king pin screws that hold the front steering knuckles fell out and the steering got sloppy. I also need to replace some other lost screws and locktite em all before I take it back out there.

I ran 3s because I could secure it in the car well with a zip tie. I was suprised that it was able to take the jumps level as long as the throttle was steady. Easy to bring the front up or down to correct with the throttle too.

For the battery holder I think I'll fasten a vertical plate that allows me to strap different packs on there using velcro. I've seen some gorilla velcro straps that include screws and some mounting washers for sale on rc-monster.

[rschoi_75]

Glad to hear you're liking it so far. Definitely change out the Mamba motor when you get the chance. The difference will be dramatic. I'd also suggest tekno straps or another brand of heavy duty velcro. My experience with gorilla straps hasn't been very good. They are too weak imo, and I've had too many failures with those straps.

[E-Revonut]

Great little truck only downfall I have is having to order parts instead of going to my lhs. Def ditch the CC motor! The VXL should run cooler geared for the same speed, a Medusa would still be much better though. The Ofna ext chassis would be a better setup too, they're not to expensive either. IMO running non stop for hours isn't good for your electronics, you should give them some time to cool off between runs, especially if your using a less than ideal motor. I know my vxl on 2s got very hot after just 1 pack in my Rustler, where as my Medusa in my CRT.5 geared for the same speed barely breaks 125*. Also IMO I would give Lipos a try, with 2 decent sized packs it leaves enough time between runs to let things cool off a bit, and if you have another truck to run while your waiting then there is no down time, Lipos seem to be much easier to fit on these.

Regardless I think you'll love the little truggy, especially with a more capable motor, regardless of your battery choice.

I actually have a ofna EXT chassis if you want it

The .5's are extremely fun little cars. I love mine

BlackedOutREVO - thanks for the offer on the chassis but I ended up buying a huge bunch of rc stuff locally to resell most and keep some. Now I have just too much stuff to get rid of at the moment.

The stock chassis is working ok for my purposes now actually but I just need to get a better mount for the servo. Maybe the mount that is close to the pinion on there now isn't even correct. It doesn't seem to be a good solid fit though it does keep the servo on there. A solid aluminum mount for the mini servo and stock chassis would be nice.

So I installed the missing screw and bushing for the front steering knuckles, using loctite. Also used some loctite on the motor mount. Nothing came loose or broke today after running for maybe an hour total. I would run for 10 - 15 minutes at a time and the mamba 4600 wasn't too hot (less than 150). I put the stock tires on there and its plenty fast.

Can someone tell me why everyone changes out the shocks? I am not all that good with suspension setups honestly. I just work on my driving mostly and try to drive the car consistently without adjusting the spring, oils, etc. I'll get a few shots of the setup now so I can get feedback from you guys on how to adjust it.

Thanks.

[GO-RIDE.com]

Originally Posted by chadr

Can someone tell me why everyone changes out the shocks? I am not all that good with suspension setups honestly. I just work on my driving mostly and try to drive the car consistently without adjusting the spring, oils, etc. I'll get a few shots of the setup now so I can get feedback from you guys on how to adjust it.
Thanks.

I have 2 e-crt.5s. One is a monster style with 1/8 shocks and big 2.2 truck tires. The other is pretty stock with stock shocks and tires. The stock one handles great, but you have to keep it really light.

My stock setup is:
Ofna extended chassis
RCM motor mount
Mamba 4600 motor
Castle Sidewider ESC
Maxamps 4200 2S batts (only 220gm)
Stock wheels
Stock shocks

My Monster e-crt.5 is at least a pound heavier and needed the 1/8 shocks to handle to weight. It is also crazy fast and jumps big triples with ease.