brushless rusty speed testing - RC-Monster Forums

t-maxxracer32 · **brushless rusty speed testing -** 04.03.2007, 03:26 AM

hey guys was doing some speed runs with my rusty the last couple days and here are the 2 diff tests i did

3s a123- 38.5 mph
12 cell rs gp3300- 43.5 mph

then the motor broke..... was going to try diff gearing and what not.... then the motor broke.... going to send it in to castle tomorow.

was wondering how much of a diff gearing would make for top speed?

thanks!

skellyo · 04.03.2007, 09:56 AM

Plug in the different gearing values into BrianG's speed calculator:

http://www.scriptasylum.com/rc_speed.html

Finnster · 04.03.2007, 11:16 AM

How did you break the motor? 12 cells on a 5700 is way too high of RPMs, over 75K! You shouldn't go over 9-10 cells max w/ the 5700.

Really those speeds are pretty poor, sounds like the truck is way undergeared as well. I can easily do mid 40s on 7 GP3300 cells on a 380C/6L (5800 kv,) so 12 cells should be into the 60s (before it blows up.) What gearing are you using?

skellyo · 04.03.2007, 12:08 PM

Quote:

Originally Posted by Finnster

Really those speeds are pretty poor, sounds like the truck is way undergeared as well. I can easily do mid 40s on 7 GP3300 cells on a 380C/6L (5800 kv,) so 12 cells should be into the 60s (before it blows up.) What gearing are you using?

Yep, I'm with ya there. My T3 with 2S lipo on a 380C 6L has been GPS'ed at 47.7mph. Also, the 380C 6L is 4817kv, not 5800kv. http://img.diytrade.com/cdimg/85838/...1082222991.jpg

Finnster · 04.03.2007, 12:27 PM

Quote:

Originally Posted by skellyo

Yep, I'm with ya there. My T3 with 2S lipo on a 380C 6L has been GPS'ed at 47.7mph. Also, the 380C 6L is 4817kv, not 5800kv. http://img.diytrade.com/cdimg/85838/...1082222991.jpg

Hmm, is this loaded then? I could have swore it was rated @ 5800, tho I bought it quite a while back, so maybe I'm misrecalling it...

Regardless, the above setup is def off. The Esc is rated for 3S lipo/ 12 cells, but the actual motor max depends on its kv (rpms/V) rating. The 5700 is ...5700 rpms/V. 12 cells is 14.4V, so that is well above the 65K rpm limit of the mamba motors. If you want to run that many cells you buy a lower kv motor like the 4600.)

t-maxxracer32 · 04.03.2007, 12:16 PM

well the motor rght on it sais rated for 3s lipo or 12 cell nimh so i figured it was ok lol...

also my gearing... i dont remember but the ratio was like 6. something

skellyo · 04.03.2007, 01:20 PM

Actually, I do think they rate the 5700 for 3S or 12cells. It's just under 65k at 3S and just over 65k with 12cells. Keeping in mind that the Mamba Max motors are rated unloaded, it should be fine...but it's gonna get hot easier.

Here's a link to a recent thread about a guy using a 5700 on 12cells in a rusty and getting into the mid 60's:
http://www.rc-monster.com/forum/show...6643#post96643

Finnster · 04.03.2007, 02:02 PM

Quote:

Originally Posted by skellyo

Actually, I do think they rate the 5700 for 3S or 12cells. It's just under 65k at 3S and just over 65k with 12cells. Keeping in mind that the Mamba Max motors are rated unloaded, it should be fine...but it's gonna get hot easier.

Here's a link to a recent thread about a guy using a 5700 on 12cells in a rusty and getting into the mid 60's:
http://www.rc-monster.com/forum/show...6643#post96643

Well, checking CC that is correct. I knew they always rated the 5700 as 3S, and the 4600 upto 4S, but I remember a thread awhile back somewhere where running 12 cells on the 5700 was considered borderline, as very good cells can push the motor upto/over the rpm limit, and it was safer to go down a bit. OTOH, people have run the 7700 on upto 8 cells, so....

Anyway, if the gearing is ~6 (like a 14/84) I don't see this as too bad. A thought was maybe the gearing is so low that the motor&batts aren't well loaded, so the rpms went over limit. but perhaps this wasn't the case then.

Was the slipper ok, or did maybe you strip the wheel hexes or something? running that much voltage w/ that motor getting that speed does not add up.

hyperasus · 04.03.2007, 08:34 PM

Ok so MM 5700kv melts at 43mph. My 2600kv Lehner does 60mph and still has power in reserve. When will people figure out that lower kv is better in the pede and rusty. I've seen a few 4600kv MM melt with my own eyes. MM motors will get your car truck moving but not for long before they burn up. They are a joke for the pede/rusty. Only good for the street speed machines that are ultra light weight and have tiny wheels. Buy yourself something much lower KV, put a 3s lipo in it, and gear to your liking.