Brushless CRT Questions

[Sower]

Ok, back on topic here guys - I have another question about the CRT conversion. Is there any real reason to go with the Lehner 1950, or is a 1940 going to work fine? And would it help to go with the 1940 hi-amp?

Originally Posted by Serum

no, most of the buggies truggies and trucks use a MOD1 as spur.

Woops...Emaxx is 32 pitch. Not sure which other Monsters are the same.

[Serum]

all the real e-maxxes are using a strobe mod1.

most of the nitro truck/buggies and truggies use mod1 as well.

[Serum]

A 1950 will have got more torque.

the 1940 is capable of running the crt around with impressive torque already.

The high-amp differs a little from the non high-amp; the wires are a direct solder instead of plugs, which theoretical makes it more efficient. I doubt if you notice any difference though.

Originally Posted by Serum

all the real e-maxxes are using a strobe mod1.

Mine is just a "make believe" E-Maxx. :-) Where do you pick up a Strobe Mod1 spur for the EMaxx? Is it expensive? I'm not building a super high torque machine but if it is more durable or reliable it might be worth the upgrade.

[BrianG]

Look in the RCM store under "gears/tranny"...

Originally Posted by BrianG

Look in the RCM store under "gears/tranny"...

Thanks.

Looks like the best ratio you can do, with that 51 tooth spur, is a 4.64 (11/51) with that spur....unless the smaller pinion (from TH) would work without pinching the motor to the tranny. The 10T at TH would yield a 5.1. I was thinking of going to a minimum 5.0 (14/70) with the 32 tooth Traxxas spur....or maybe even a 6.0 (12/72) if I needed more torque.

Goal is to dupe the stock Titan power, but with more run time. Looking at a 3S Lipo and a Feigao 7XL.

[BrianG]

It sounds like you want a really low geared maxx. You could keep the two speed tranny and run something more like 51T/14T or 15T. That would give you low end torque in first gear and high speed in second. If you have the tranny locked into second, then you don't have as many options. Although, honestly, first gear is useless with BL power.

Also, I'd personally go with a little higher voltage, like 4s, and the 9 or 10XL. That way the batts are balanced 2s on each side. The 9XL will still have more power than the titans and runtime will be better. The 10XL will have even better runtime, but be slower.

[Sower]

Originally Posted by Serum

A 1950 will have got more torque.

the 1940 is capable of running the crt around with impressive torque already.

The high-amp differs a little from the non high-amp; the wires are a direct solder instead of plugs, which theoretical makes it more efficient. I doubt if you notice any difference though.

Thanks Serum, that's great info. I wish I could see the difference somehow to know if I want to run the 1940 or the 1950. Does anyone have video of a truggy with the 1940 and one with the 1950?

Originally Posted by BrianG

It sounds like you want a really low geared maxx. You could keep the two speed tranny and run something more like 51T/14T or 15T. That would give you low end torque in first gear and high speed in second. If you have the tranny locked into second, then you don't have as many options. Although, honestly, first gear is useless with BL power.

Also, I'd personally go with a little higher voltage, like 4s, and the 9 or 10XL. That way the batts are balanced 2s on each side. The 9XL will still have more power than the titans and runtime will be better. The 10XL will have even better runtime, but be slower.

The main purpose for the brushless is to get a maintenance free truck that will have long run times. Don't want to mess with locked tranny, UBEC...etc.

If I run two batteries I will keep 'em in parallel to get even longer run times.

I'm running with an inexpensive MambaMax so I didn't want to push it by going too high a gearing for fear I'd overheat it.

Thanks for all the advice, BrianG.

[BrianG]

No problem.

Still, I think the 10XL on 4s (or 12 cells) would be the thing you are looking for. It's more efficient to run higher voltage on a higher turn motor since there is less current draw - and the MM will stay cooler too because of that. Gear it conservative and it should be a very stable (temp-wise) truck with more speed and power than the Titans with the hassle-free maintenance you want.

And even though you don't want to deal with locking the tranny, I think you'll find yourself leaving it in 2nd gear because 1st is honestly just useless. And removing those extra parts (shift servo, linkage, shift fork, extra gears) makes the tranny simpler, lighter, and increases reliability.

And as far as the BEC goes; even at 3s, the MM will generate heat because of the BEC. I always recommend a switching BEC at anything over 6 cells/2s. Say you're running 3s and servo(s) drawing 2A, the MM BEC will be forced to dissipate over 10 watts of power as heat. That's really a lot even though it doesn't sound like it. The switching BEC takes all that load off the MM and does it more efficiently too (and gets more efficient with higher voltage).

Just my $0.02. Good luck and let us know how your truck runs when you get it done.

[BP-Revo]

A 10XL on 12 cells would be somewhat slow no? I'd run at least a 9XL, if not an 8XL.

Originally Posted by BP-Revo

A 10XL on 12 cells would be somewhat slow no? I'd run at least a 9XL, if not an 8XL.

I thought about the same thing.

Perhaps I wouldn't have to gear it so low with a 10XL...or a 9XL....which would make up for the lack of kV. The extra efficiency...about 10%, should yield higher run times...which is what I was going for in the first place. Hmmmm...except, running at a lower voltage knocks down the efficiency...so maybe the difference is only 5%.

I placed my order for the gears and motor last night. If I make a change it better be early this morning.

[BrianG]

Yes, it would be a bit slow on 12 cells, but I was trying to come up with a reliable system that roughly equals stock performance and speed. I run 14 cells on a 10XL on a Revo and it's about 30-35mph. I run several battery packs through it and temps are usually below 135*F on all but the hottest days. But then again, I am geared kinda high.

[Sower]

Ok, here we go. I have another question. I just went through the motor selection on Brian G's site. Awesome I might add.:027:

Anyway, every time I plugged in my info it said to run the Lehner 1940 - not the 1950. The only time it told me to go 1950 is when I bumped the weight up to 12 pounds or more. I plan on running about 11 pounds based on GD's truggy. His was the RTR with the 12000 MaxAmps, and mine is the CRT Pro and I plan on running either two 4350 Enerlands or two 5000HV MaxAmps. So, am I pushing the 1940, or is that really what I should go with? The 1940 is in stock right now too, while the 1950 seems to be taking forever.

Oh, by the way, I was plugging in a desired top speed of 45 mph with the Kyosho 46t spur and a 14t pinion. What do you guys think?