safe to run a 1717 on 4S in a truggy? pics included
 

Ok,

I just got done with my Caster K8T conversion, which included stuffing a CC 1717 1580kv car motor into the chassis. I had to use an EliteRC motor mount from a MBX6 to get the proper motor clearance. With this mount I can run as low as a 15, maybe a 14t, pinion.

Now, I had ever intention of running the setup using a pair of 3S batteries in series so that I could acheive long enough run times to complete a 20 min main without needing to change batteries. I'll still likely do this, but for now, I have only 4S batteries, with the exception of a pair of 3S Zippy batteries that I only plan to use for testing until I can get some new batteries.

Would it be safe to run 4S in this setup? My 4S batteries are the Hyperion G3 25c 5000mah batteries. Or will the motor try to draw too much from them.

I'm currently geared 18/46. Here is how the speed calc pans out.

On 4SDifferential Ratio: 4.3
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 18
Total Voltage: 14.8
Motor KV: 1580
Tire Diameter (inches): 5.8
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.56 : 1
Total Ratio: 10.98889 : 1
Tire Circumference (inches): 18.22 inches (462.82 mm)
Rollout: 1.66:1
Total Motor Speed: 23384 RPM
Vehicle Speed: 36.72 mph (58.98 km/h)
Effective KV Value: 1580
KT constant: 0.86 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

On 6SDifferential Ratio: 4.3
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 18
Total Voltage: 22.2
Motor KV: 1580
Tire Diameter (inches): 5.8
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.56 : 1
Total Ratio: 10.98889 : 1
Tire Circumference (inches): 18.22 inches (462.82 mm)
Rollout: 1.66:1
Total Motor Speed: 35076 RPM
Vehicle Speed: 55.08 mph (88.47 km/h)
Effective KV Value: 1580
KT constant: 0.86 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

Now on 6S with a 15t pinionDifferential Ratio: 4.3
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 46
Pinion Tooth Count: 15
Total Voltage: 22.2
Motor KV: 1580
Tire Diameter (inches): 5.8
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 3.07 : 1
Total Ratio: 13.18667 : 1
Tire Circumference (inches): 18.22 inches (462.82 mm)
Rollout: 1.38:1
Total Motor Speed: 35076 RPM
Vehicle Speed: 45.9 mph (73.73 km/h)
Effective KV Value: 1580
KT constant: 0.86 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

It definately looks like the 15t on 6S puts the RPMs in the sweet spot. Again, that is where I plan to be eventually. But man, 45mph is still a bit fast for racing.

ben

Hello,
It will draw the same current as a 1515 geared for the same speed, so don't worry. Maybe the 1717 will run more efficient too so even less amps ;)

Ben,

The 15T doesn't affect ''Total motor speed'' you can see the RPM is the same with 15T and 18T.

About completing 20 minutes, gear as low as possible. If 15T is as low as you can get and the speed is to much try lowering throttle travel. This will also reduce topspeed / A draw if I'm not mistaking.

Another option would be to get a 1520 (1600kv) in there. Still very efficient but not as thick (so smaller pinion might be possible) and heavy as the 1717.

Hopefully you can complete the 20 minutes, it's a long time :)

Under hard racing condition (europeean track), my 1520/1Y 6S geared for 39mph (13/46) in my mbx5t truggy last 12 minutes with 6S 2950mAh 35C hyperion. I don't want to use bigger batteries because I want the lighter possible truggy.
IMO the 1717 is useless and too heavy for a truggy (80-100 grams more than the 1520). The best truggy choice is (for me) the 1520/1Y. I even run a 1520 in my buggy on 4S, a little heavy (60 gramms more than the 1515) but very efficient.

Here is a video of it running on 4S last weekend during a practice session. I forgot to time this run. Then later when I was prepared to time my 6S run, I crashed on broke the right rear a-arm on the second lap. :lol:

http://www.youtube.com/watch?v=y4CV2k60svE

When I placed my order, I did it very spontaneously in response to the big motor sale. I know now that I should have gotten the 1520 motor instead, but I was trying to get the lowest kv rating I could.

I need to get some quality Hyperion 3S batteries to be certain and do a timed run. For now, I'll have to use the Zippy packs I do have to test. I don't mind a heavy truck, as long as I can make it handle and last the distance.

ben

Well I finally got a chance to time my runs. I'm a pretty disappointed with the results.



On 4S 25c 5000mah Hyperion I was able to get 13 mins. On 6S 40c 4500mah Zippy I was able to get 15 mins. My 6S setup is pretty old and the batteries are probably near their end of life. I assume with some new quality batteries I can get more run time, but I'm doubting I can get 5 more mins.



The truck is heavy no doubt, but I haven't weighed it. I ran it for one session with a pair of 4S hooked up in parallel and was able to make 20 mins no problem, but that really made it heavy. I ended up bending the rear shock tower and ripping it from the bulkhead after tumbling a few too many times.



ben

That's normal, a 4S 5000mAh battery has less electrical quantity than a 6S 4500mAh. You should have tried with 6S 3300mAh to get the same runtimes ;).

I was hoping for a 20 min runtime on 6S. Not enough eletrics here to run our own class, so we get lumped in with the nitros and 20 min mains. Battery changes have proven to be troublesome.

I think the overall weight of the truggy is really hurting me the most. I'm not prepared to drop endless amounts of money on the truck though. Already spent too much. I may have to be content with having a truck that is really only going to be good for 15 minutes in most cases.

ben

What speed your truck is geared for ? My truggy geared for 39mph on 6S 2950mAh with the CC 1520/1Y do 11-12min under race conditions. Try maybe a lower gearing if you want get the 20 minutes... Set timing to 0 and punch 70-80% (enough for racing).

I was running with an 18t pinion, which puts me at 55mph at 6S. But, I had the EPA on the radio turned down to 75% which makes the top speed about the same as when on 4S with the same gearing. I'm running 0 timing and no punch control.

ben

OK,
Use punch control, it really kills the amp spikes during acceleration. The EPA at 75% isnt really good for the ESC (bad efficiency of the transistors). You really can't gear down with the width of the 1717 ?
If not, the best solution would be the 1520 1600Kv with 13T pinion on 6S... Try to get one, only 65 bucks.

I thought it was the other way around. I though using punch control killed the efficiency. I know I can fit a 15t pinion on. I'll see if I can get smaller.

I really wish I had gotten the 1520 instead. I always learn my lessons the hard way. LOL. Honestly, I'd like to have an even lower kv motor like a 1350, but CC doesn't make one.

ben

Try the torque control (not the punch control...) -- it really will do a better job of limiting current. You will be surprised how much more runtime you can get, and it won't limit your top speed (when setup correctly...)