armourbl

iTrader: (44)

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 4S
Differential 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 6S
Differential 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 pinion
Differential 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

IOP_Racer

iTrader: (14)

It should work fine especially with the low gearing. Just take it easy and monitor temps.

Duster_360

iTrader: (21)

Man, that looks nice Ben! Is there any clearance behind the motor? Can't really tell from the pics.

The motor and esc ought to love 4S and run cool. I'd watch the batts for temp. They might get hot trying to supply the 1717 if you push it. That'd be my only worry.

armourbl

iTrader: (44)

Yes it is close. I had to sand down the radius on the arm quite a bit to gain clearance. If only the motor were about 1mm shorter. I also made a brace that extends from the center diff to the front bulkhead to stiffen up the front and prevent it from flexing. I ran it today at the track it performed flawlessly -- until I clipped a landing and busted the right rear a-arm, shock end, and sway bar eyelet.

Here is a pic of the carnage. I'll post a video of the crash as soon as I get it uploaded to YouTube.

ben

armourbl

iTrader: (44)

On 4S, getting to know the truggy. This is literally my first run of the truggy with this motor and on the track.
http://www.youtube.com/watch?v=y4CV2k60svE

On 6S, with the EPA dialed back to 70 percent. I ended up clipping a landing with the rear, and broke the right rear a-arm and then some. This ended the day because I didn't bring my spare a-arms.
http://www.youtube.com/watch?v=U8KZ7n_VUv8

Duster_360

iTrader: (21)

You're going to be dangerous with that thing, it looks like its almost dialed already and you're really just getting started! Glad you were able to generate some clearance, 1717 is a big motor!

One more ques, is there anything supporting the back of the motor, or is it suspended completely from just the front mount? Reason I ask, I used to run a 18th scale with a really big motor and bent every mount I put on it. I finally realized the weight of the motor and shock of landings was too much without a support for the endbell. I'm worried about that with the CD mount I'm trying to rig for one of my 1717s in my UE Lightning.

armourbl

iTrader: (44)

I thought about that, but the EliteRC mount is pretty stout. I'll have to keep a close eye on the mount screws in the chassis. I might see about putting a support under it made from plastic so it won't wear on the motor or chassis. Thanks for the suggestion. I'll definately look into it.

I have to say, I'm really liking this truggy. It was turning on the power alot better than I ever could with my D8T conversion. That motor makes it even better. I'm really hoping for some good run times from it. I need to pick up some quality 3S batteries and do some more testing.

ben

Duster_360

iTrader: (21)

That's what I figured about the way that mounted. What I used to solve my prob was super simple, cheap and effective. I bought an eraser (the kind you use by hand, not one on the end of a pencil) and cut it to match the curvature of the motor and left it flat on the other end. I cut it longer than the space and compressed it slightly with the motor. I never bent another mount and it never moved.


Your Caster is impressive, the balance looks solid and it shows on the track. Flies pretty nice too.

armourbl

iTrader: (44)

Thanks for the comments.

The only issue with a support is the EliteRC mount moves the motor at an angle. I could justs use one size pinion since I don't really go to a variety of tracks. But if I want to change the pinion, the support will either be too big or too small.

ben

armourbl

iTrader: (44)

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

IOP_Racer

iTrader: (14)

You could probably get 20 miniutes out of 6000 mah batteries pretty easy as you are getting 15 minutes with 4500 mah.

armourbl

iTrader: (44)

I was thinking of selling the motor and getting a much lower kv motor, like a 1350kv. Would that be heading in the wrong direction?

ben