6S CRT.5 Neu motor question

[VintageMA]

Originally Posted by sleebus.jones

If you're going to run 6S on a MM, you are going to be just over the 25v limit with a fully charged pack. I would think that 5S would be more than plenty for your application?

I'm surprised you're having trouble with heat, but a 130 degree LiPo is HOT, as in ready to burst into flame. I run a MM 5700 in my T4 stadium truck with 3S A123. I get 13+ mins runtime, motor temp = 130ish, ESC = 115ish, Batts = warm. Have you checked driveline for binding, too tight gear mesh, etc? I think something else is at work here.

I think a lot of it has to do with my bashing style (I don't live anywhere near a track right now) which is a lot of WOT acceleration and running with some hard braking in large parking lots and grass fields. The drive train is very smooth, the gear mesh is nice with just a littlespace in the gears for chassis flex, and I blow all the in's and out's till they're spotless with an air compressor after every run. (Translation - I am a anal obsessive compulsive clean freak)

I know that the MM won't support 6S so that means either moving to a Quark or a MMM hen available. There is also a substantial capital investment involved in moving to 6S as my balancers only work to 5S and I will have to get 6S packs (which are to $$$ in the 2200mAh-2600mAh range) and may break down and get a TP 1010C charger with 210V balancer (been checking them out and like how they can work together). I've been using a TP 205V balancer up till now and all my packs have TP balancing connectors.

This is why I'd like to hear from some more people that the investment will pay off to some extent (other than that it becomes an expensive experiment, but I'm dying to try something new with spring here not having spent much $$$ on RC over the winter). Plus I expect the 6S investment to pay off when the e-revo is available as I hope to get one towards the end of the year.

[jhautz]

Just a thought... Here is a cheap(er) way for you to try and reduce battery heat and increase run time.

The Lehner motors can be reconfigured to run in eithe delta or wye wind by changing the sloder path on the back of the motor. If you change your 1930/6 it will become a 1930/10 at 2090kv. On a 4s pack that will give you around 30K motor rpm. You could run that on your MM and reduce amp draw a bit from your current set up and you could do it all with the ESC and Motor you alreay have.

BTW: I'm curious what batteries you are running. I run a 3s 3700mah Polyquest, MM and Hacker 8L (3019kv) and don't have any heat issues and get run times of easily 15-20 minutes beating it very hard. I actually have a 1903/6 here and was thinking about putting it in the CRT.5 to see how it ran.

[VintageMA]

Jeff - I'm using the MA 3S-5000mAh packs (about a year old now, but were strong when i first bought them).

I started out with the same motor as you B50 8L and was getting just about the same runtime as you. Then I got the 1930/6 and with the same gearing got a great speed boost and things were just in check (if maybe close to the edge).

With the RCM extended chassis and 30 series wheels it seems the current draw has gone straight through the roof.

I actually REALLY like your idea on re-configuring the LMT to a 1930/10 to lowe the KV - I hadn't even thought of that. I didn't want to have to ditch the LMT - I love their motors. Are you sure changing from a delta to a wye config will produce that end result?

[BrianG]

Originally Posted by VintageMA

...With the RCM extended chassis and 30 series wheels it seems the current draw has gone straight through the roof.

Well, the extended chassis added some weight, and the larger tires effectively increased your gearing, so that makes sense. I would've gone down at least 2 teeth on the pinion to keep close to the same roll-out ratio and to help compensate for the added weight. Of course, this assumes you don't mind losing a bit of top speed.

[VintageMA]

Originally Posted by BrianG

Well, the extended chassis added some weight, and the larger tires effectively increased your gearing, so that makes sense. I would've gone down at least 2 teeth on the pinion to keep close to the same roll-out ratio and to help compensate for the added weight. Of course, this assumes you don't mind losing a bit of top speed.

Unfortunately, when I put the larger wheels on, I did re-calculate for the larger diameter and went from 17/46 to 14/46. Still heavy current draw.

Running 3-10-1 for differential weight (even put in new oil when I broke it down and moved to the new chassis) to prevent too much unloading to the front wheels - wonder if that may be affecting things.

It's weighing in around 4.5lbs - is that consistent with you guys?

[jhautz]

I dont know the weight of mine, but Im sure yours is heavier. Im running stock chassis and tires with a smaller lipo.

I'll try and get a weight for you to comapre against tonight.

[VintageMA]

Jeff - that was an awesome idea with the reconfiguration of the LMT - thank you very much!!

A little tricky reconfiguring the solder joints but I got it done and made sure the solder was nice an thick to avoid creating a fuse as per your old thread from last summer.

Went back up to a 17/46 (~39mph) gearing and with 4S pack measured peaks around 30 Amps just boogying around the house (whereas I would hit high 40s with the previously described config).

I probably won't get out for a real run until the weekend, but I am very excited with a setup that may work great and save me ~$500+ in the long run.

The big bummer is that my order for a Neu 3900mAh 3S pack just came in - don't know what I am going to do with it now, but maybe hang onto it for some ~30mph running around - probably get some long runs with it now.

Once I get a full run and can check the amp peaks and am sure this setup will work I then ned to find a nice 4S pack that will balance out well with the vehicle. The motor (230g), servo (60g) plus heat sink and fan come out to ~300grams. I had gotten the Neu 3.9Ah 3S pack cause it weighs in at 306grams and almost balances out the motor side of the vehicle perfectly. Maybe a NEU3200XP 4S (337.5g) or a TP3300 eXtreme V2 4S (351g) - both rated 25C.