Just won a crt.5 with mikes chassis...did I do ok?
 

I decided I wanted to do a crt.5 brushless converison. I found this on ebay
http://cgi.ebay.com/ws/eBayISAPI.dll...MEWN:IT&ih=022
And just won it. It was a little more than I planned to spend (was hoping to win it for 160-170). It actually worked out reasonably well as the end price was 195 (210 after shipping). There was a paypal coupon for 10% off your next purchase so my final price shipped ended up being 190.

Considering mikes chassis kit is 150 new, and a crt.5 roller is around 150-160 I think i did ok.

now to get it and install the MM/VXL motor on 3s. I think it should make this little truck RIP!

For those of you with a crt.5, what servo do you run? I have the stock traxxas 2055, but am thinking maybe a z590 would be a little quicker/stronger. I was looking at a 645mg or the blue bird, but think 160-190 oz/in of torque is overkill for a truck this size.


- Mike

That was one of our forum members! I remember seeing that here!

Thats a awesome price!

For a servo, I run a Futaba S9551 low profile. I will be updating my build thread soon I hope. But something with metal gears is always good

Ahh good deal. Its hard to tell from the pics, but it looks to be in good shape. Plus its cool that its all black annodized (I love all black). Some black wheels and a black body and this thing will look tight!

Good deal but I think this is a BCE chassis not mikes - Mike's chassis IIRC does not have the x drill out behind the motor mount...

Good deal anyway

Its the RCM chassis. I remember it on the forums here. And his chassis has the X, I always hated it because my speedo wouldnt like to stay put because there wasnt much for the tape to stick to:mdr: Shoegoo fixed that:na:. You can tell by the holes drilled in the chassis, and the way its milled out. Plus it has the servo mounts, and RX mount thing to

And on the servos, mine has 133 of torque, and its more then enough. But over kill doesnt hurt lol. And you know I love blacked out stuff, LOL

I'm using a Spektrum z570 I beleive and it works just fine, I'm guessing the z590 would be even better. If your running stock size tires it doesn't take much to turn them.

Im running 2.2 tires, with 8th truggy rims. So there big =) LPR's, 2.2 style!

My .5 is using an Airtronics 359 servo. It's very fast at .10 sec, and has plenty of torque at 200 oz/in. And BTW, there's no such thing as too much torque when it comes to steering servos :lol:.

Alright I think I will go with the blue bird that has like 190oz and .15 just because they are pretty cheap and has the same speed as the z590, but double the torque. This should help turning the big tires I plan to attempt running on this thing :)

If I have heat problems or its too tippy I will probably just end up with 2.2's on her

Thanks for the help guys!

Yeah, go for it! That servo should do perfect!

Get some pics when its done!

Will do!

I just noticed the little "special offer" pull tab on the side of the forums. I clicked it to pull it back and it shows the crt.5 chassis kit, but it looks different than the picture of mikes crt.5 he shows in the store. This chassis has a billet battery brace and what looks like more milling on the chassis. Is this a whole new setup, or is it the same and he just has a velcro strap on that lipo pack in the pic?

I will def get some pics when its all said and done. I am stoked to get this little truck! I think it will be perfect for bashing in smaller areas. I usually look for more agressive terrain for bigger trucks, but everyday terrain (curbs, small hills etc) will be more challenging (fun) for this little truggy!

Pic in the store is the updated current chassis/kit. The one in the "tab" is the prev or older version.

O ok gotcha.

I just realized I am going to need to order a pinion before I can run this thing. What do you guys suggest I get for a starting size?

I will be running the stock tires, some 2.2 tires, adaptors with 1/8 buggy tires (pretty lightweight, but tall as well) and lastly some masher 2,000 tires. I am guessing I wont be able to run all of these tires on one pinion, but finding a starting point would be good without just guessing!

Think I should just get one pinion size (I need a reducer too, so its already 17.00 for just one pinion!). How about changing the spur on the diff, is that a pain to do? Again I will be running MM/VXL motor on 3s 5000 packs. I would like 35-40 mph top speed, good run times and hopefully keep the heat down.

I would rather be geared a little low to avoid heat build up/strain on the electronics (ie...heat). so should I go with like a 14tooth to start with? Or even lower?

You can use the bore reducer in more than one pinion. With that kv of a motor on 3s a 14 will probably work well with up to a 4.0" tire.

Try using BrianG's spped calculator
http://scriptasylum.com/rc_speed/_top_speed.html

lol thanks for the link, but I dont even know half of that info to properly fill out that chart.

I think since I plan to run 1/8 buggy tires a good bit of the time (being 4inches +) I will try a 12 tooth pinion to start with. Then if its geared plenty low with smaller tires i will jump up to a 14/15 later once I get a few runs in.

even with a 12 tooth on 3s think I will still be above 30 with stock tires? road rage 2.2's?

Differential Ratio: 3.25
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 47
Pinion Tooth Count: 14
Total Voltage: 11.1
Motor KV: 3500
Tire Diameter (inches): 3.5
Tire Ballooning (inches): 0.3
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 3.36 : 1
Total Ratio: 10.91071 : 1
Tire Circumference (inches): 12.88 inches (327.17 mm)
Total Motor Speed: 38850 RPM
Vehicle Speed: 43.43 mph (69.77 km/h)
Estimated Adjusted Speed: 41 mph (66 km/h) - 6% loss
Effective KV Value: 3500
KT constant: 0.39 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...


The first couple fields you can use the presets, crt.5 diffs, center diff direct drive for tranny, stock is a 47t spur

14t pinion on stock tires will give you about 40-41MPH depending on ballooning of the tires it may be more

Sweet, thanks for the help! 40-41 on a 14 tooth? Damn those stock tires are pretty short too (cant be more than 3 inches?)

I just looked at the field for circumference and you put in 12.88. I converted that and it comes out to be 4.1 inches. Stock tires are pretty tiny right? More like 2.8- 3 inches tall? I tried checking tower but they only have the width for the stockers.

I would like 40mph to be the top speed (45 is fine as long as im not getting serious heat). Maybe I should swing for the 12 tooth pinion so im safe for the bigger tires?

stock tires are about 3.5" tall and I put in a ballooning radius of 0.3" so that does equal 4.1". However at those speeds the ballooning may be greater than 0.3" which will increase your speed even more. IMO I'm not sure that your going to be able to gear a 3500kv motor down enough runnin 3s to run any bigger of a tire than stock. A 12-13t will prolly net you 40MPH with the ballooning you'll have at that speed. To figure in bigger tires your pinion is going to have to be crazy small unless those bigger tires don't balloon as much. I know that my slash tires don't balloon as much but geared for about 38MPH they still balloon about 0.25" on the radius. IMHO to run 3s I'd pick a little slower of a motor. Personally I think I'll be staying with 2s on my crt.5, my Medusa motor runs plenty cool, much cooler than my vxl did in my rustler, that thing got HOT!

wow stock tires are much taller than i would have guessed! I guess going from a 3.5 tall tire to a 4.0 - 4.5 will not be too drastic of an increase. The 1/8 tires do not balloon that much as the sidewall is so thin so that should help.