My CRT.5EXT...;)
 

Hi guys, I finally got some time to get some pics of my BL CRT.5EXT or is it CRT 1.0? Sorry theres alot of pics!

Specs:
RC-M motor mount Geared 14/46
Custom battery mount
Gorillamaxx battery strap
Proline 2.2 Bow-ties
Traxxas stampede front wheels
Original Jammin full size CRT wing that was modded a little...

Electronics:
Feigao 10L motor with RC-M heatsink/clamp
TrueRc 4200mAh 4s (15c cont.)
Temporary Futaba 3004 servo.
Futaba FASST
UBEC from TrueRc (unsure on the brand)

So far thing runs awesome!

PICS:
http://i125.photobucket.com/albums/p...1/IMG_1675.jpg
http://i125.photobucket.com/albums/p...1/IMG_1669.jpg
http://i125.photobucket.com/albums/p...1/IMG_1674.jpg
http://i125.photobucket.com/albums/p...1/IMG_1680.jpg

Some more...

http://i125.photobucket.com/albums/p...1/IMG_1667.jpg
http://i125.photobucket.com/albums/p...1/IMG_1684.jpg
http://i125.photobucket.com/albums/p...1/IMG_1671.jpg
Getting ready to take the monster triple at the RC-M Bash...:yes:
http://i125.photobucket.com/albums/p...1/IMG_1644.jpg

Bye :yipi:

Cool Beans! Love the table too, looks exotic :-D

truck looks great bro..
phil

Thanks for the compliments guys.

Question, before I was running 3s and geared for 38mph and pulled 90amps. Now running 4s re-geared for 38mph I get a little over 90amps. Shouldn't I pull less amps? I am pulling more watts though; from 700 up to 1200+...

Heres a graph; Batt holds 3.375v/cell@ 90amps! Its 15c cont. which is 63amps, 20c burst which is 84amps, so I thinks thats pretty good!... @65amps I get 3.575v/cell
http://i125.photobucket.com/albums/p...tal101/crt.jpg

So why didn't I get a reduction in amps?

Bye:mdr:

I think your findings illustrate what Brian is always telling me. With higher voltage input more amps will be drawn, up to a point. Not sure when this stops, or what it all means. I have a feeling thyat you had your 10l geared high on 3s and it was pulling 90amps due to heavier load. Now it is geared down it still pulls the same or more amps, but is most likely more effecient and may heat up less? The lower gearing will help the heat issue, it did for me when I went to 4s on my 10l.

Seems logical, With 3s I was geared with a 20t pinion, same as your crt.5 you had right? I get the same temps on the motor (145f) but the esc and batt are much lower(like 30f lower). So????????????????????????....Maybe Brian could chime in?...

Bye

Yeah, the motor temps on feigaos suck, you have to gear down to get them to stay low on a long run. The batt and esc are not working as hard now as they were on 3s with the 20t pinion. Plus the motor has greater mech. advantage with the smaller pinion gear. Som educated spouting by Brian would be nice!

I wish people would stop posting about these CRT .5 because I CAN'T AFFORD ONE.

I think if you you want to get lower amp draw you must put in a higher turn motor along with the extra cell. You should then get similar performance with a little better efficiency.

What's the largest size Neu motor that will fit in these things and will run well off of 3S with a Quark Monster Pro?

Well, a 1512 would be nice (around 2600-3200kv).

I'm thinking of putting my Neu 1515 1y in the crt.5ext. Question, would I effectively lower my amp draw because of the lower kv or just pull more amps because of it being a bigger motor?... I pull about 125amps and 1800+ watts(on 4s) out of my revo with this motor so???????...

Bye:mdr:

Wow, that would be insane. I wonder if this would be a good platform to use in the next RCCA world speed contest. If so this may be next on my list.

Very nice truck. Man... I wish I could have been there to see the CRT.5 fly over that triple. Now that would be a sight to see. :yes:

Need help in my quest for lower amps...
 

Hey guys! I have a couple of questions on how to lower my amp draw in my crt.5ext.

Specs:

initial setup:
Maxamps 3s 4000mAh w/Feigao 10L geared for 39mph = 90amps (max) and 800 watts

Next:
Truerc 4s 4200mAh w/Feigao10L geared for 39mph = 90amps (max) and 1200 watts. Now, shouldn't I have lowered my amp draw?

After:
Truerc 4s 4200mAh w Feigao 9xl geared for 40mph = 100amps (max) and 1300 watts.

Now, I would like to lower my amp draw to about 60amps (max) if that is possible? What motor would do that? Pretty much my reason for going to 4s (besides the raw power) was to lower my amp draw to put less strain on my lipos. (at 100amps the voltage drops to around 3.3v/cell, my lipos are rated for 63A cont. and 84A burst) So, ?????????????? help would be appreciated!

Bye:mdr:

If you could find a motor like a Feigao 12L or something like that, then you could lower your amp draw on 4s.

The problem with changing gearing to maintain the same top speed when increasing voltage with the same motor is that the motor's resistance is still the same. V = IR, and so since the resistance (R) is the same, when volts (V) increases, so does current (I).
Changing the gearing just means the motor won't pull as much current as if you kept the same gearing when increasing the voltage, but since it's still the same motor, the motor is capable of pulling more current.

You need to drop to a milder lower kv motor... from teh 10L to a 13L. Then you gear for the same top speed.. and you should have similar performance (and max watts) so the amps should drop accordingly.

This should be much more effective than simply regearing the same setup and boosting the voltage. That 10L will "want" to make the most power it can, even if you gear down. What it's doing on 4s is accelerating harder and spinning at higher rpms than it did on 3s. Even though the top end is the same.

Without swapping motors, then what you could do to loower the amps... is soften the trigger finger (or set radio/esc to very mild accleration curves) to compensate for the fact that it has more power on tap.

Cemetarygates,

What are the handling differences btwn the stock chassis and extended RCM chassis? Did you have to change any of the suspension set ups?

I just rcvd the RCM chassis, but will not have time to build it up for a couple of weeks.

You will indeed lower current by both increasing voltage AND lowering the gearing. You will also increase the potential amp draw by increasing the voltage. This is why you may see high amp spikes

What you should be looking at is the average amps not the amp spikes. You may see a 91amp spike but your average amp draw should have decreased in comparison to the 3S setup with appropriate gearing.

For instance, I have recorded an average of 40amps with 8S A123 and an average of 35amps running 10S A123's with appropriate* gearing

It looks like you had an average amp draw of 8.38 amps. I would guestimate that 3S would increase the avg amps to ~ 12+ amps

I would be interested to see what you record with a 3S setup with appropriate gearing.

* appropriate gearing is the gear ratio required to meet the same speed at any given voltage

well, with the new chassis I can push much harder into the turns without flipping the truck. I also put some HPI MT firm springs in the rear.


Heres the info:

3s w/10L = 13.13amps avg.
4s w/10L = 8.38 amps avg.
4s w/9xl = 12.10 amps avg.

So, is it safe to run the truck with the 9xl(100A spikes) and not harm the battery? Thanks for all you help everyone!

Bye:mdr:

Well, if you overheat teh pack you could damage it or it could catch on fire. You should not let a Lipo pack's temp go over 140deg F.

I think 100AMP burst is the probably reaching the limits of 15C cells but I do not know for sure. This is a question you should pose to the manufacturer so you get a definitive answer.

Thanks for your answer, I'll call Dan @Truerc soon. BTW my pack only heats up to around 95F, motor is at 140F, and the esc is at 135F.

It says on the site to use Traxxas Rear Wheels but you are using Traxxas Front wheels. Are they basically the same?

Ok, just found out on Tower Hobbies that the rears have a greater offset. I have owned 2 Traxxas Stampedes and I didn't know that, lol