6S CRT.5 Neu motor question
 

I've been reading that a 1506 should be fine to push a CRT.5 and a 1509 may be overkill. Looking to move from a 3S to a 6S setup to reduce amp draw and increase efficiency gearing for a modest 40mph - nothing crazy. Would like to keep the motor RPMs around 30-35K.

A few choices: (assuming quality LiPos holding 3.5v/cell under load - 6*3.5 = 21V)

1506/3Y 1850 = 38850 rpm

1509/2.5Y 1450 = 30450 rpm

So which do you think would run cooler with less amp spikes and overall draw?

The 1506 is a smaller motor and will draw less overall, but with a higher kv it may pull larger spikes trying to spin-up.

The 1509 will have more torque and a more mellow spin-up amp draw, but it's a larger motor and the added torque will come at the expense or more current.

I'm only getting 10 minutes run-time with 3S and a LMT 1930/6. Motor and esc cool, but lipos are touching 130*.

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:lol:)

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.

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.

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?

Hm, your bashing style sounds very similar to mine, because it's pretty freakin' flat around the house. I probably run mostly on concrete tho. I still dont' see high temps. *shrug* Sounds like the drivetrain is set up just like it's supposed to be. Have your entered your stuff in the top speed calc to see if it's set up to run the speed you want? it's possible it may be set up to run much faster, but they system can only pull it so far (which may lead to the hot batteries you describe).

I would warn against a Quark. I have heard of many many instances where 6S = smoke. As far as i'm concerned, where big ESCs are concered, the MMM is the only way to go. We all know it's going to be designed beyond tough, and their CS is excellent.

Doing some digging I found this link:

http://www.lehner-motoren.com/downlo...use_s10-22.doc

from an old thread of Jeff's. I'm going to give that a try as I have a 4S 4000mAh pack lying around.

It'll end up saving me spending $$$ I don't have right now. But I really wanna buy a new charger :tongue::tongue: MUST..... RESIST..... URGE..... ;)

That is exactly the documant I was going to link you to.

And yes it works. I did it on my 1930/6 and made it a 1930/10 for a while and ran it in a 1/8 buggy on 5s and a Quark 80B. Ran like a champ, but just a little to small of a motor in the long run for the 1/8 buggy. Should haul a .5 around with some authority though. :yes:

Dont forget the external BEC on the MM for 4s though.

No worries there - ever since I did a test and found the MM heats up a lot just from using it's BEC on 3S I've been running a CCBEC for anything over 2S. Thanks for the reminder though.

I'll try this tonight and let you know how it goes.

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?

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.

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.

I am currently running a novah hv 6.5, with a MM on 3s lipo. I had a maxamps 4200 pack, and it puffed first run. Kind of disappointing, as I had a 15t pinion in it, and it was not that fast.

Having changed almost every vehicle over to 5s, and recently making a few 8s trucks, I can say that going back to 3s sucks. I would almost say that if you can, go to 5s lipo and an 1800kv-2000kv motor. Gear it for 45mph, and the performance will be great!

I have a LS10, which is almost identical size/weight to the .5 with the ext chassis and truck tires. I ran a hacker c50 14l on 3000 5s lipo thru a quark 65 and it was ridiculous.

I am sure just stepping up to the 4s and lower kv will make a huge difference. 3s just seems to run at the edge of what most appropriately sized batts can provide. I plan to run a 5000 neuenergy 3s 25c pack in my .5, but need to move some stuff around. Then I will gear up to a 17t pinion, as the 15t is a bit slow, but that may be my 2100 3s maxamps packs (2 wired in parallel) dropping voltage under load.