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View Full Version : For the Mamba 8000Kv guys...



Smoothound
04-16-2005, 06:01 PM
Just curious what gearing you are currently pulling and what batteries you are using.

I'm running a 10T pinion currently with a 3s Thunder Power 1320 pack but my temps are getting a bit on the high side motors hitting 180*F and the pack is 125*F.

I'm planning on running 3s2p around 800mAh but it appears the current TP offering is 730 or 900 but the 900's are a bit big to fit and the 730's are probably a bit on the small side...

Smoothound
04-24-2005, 10:22 AM
To fix it I first thought of this...

Smoothound
04-24-2005, 10:25 AM
In the end I did this...

hkopium
04-24-2005, 12:59 PM
To fix it I first thought of this...

Nice mod man, how did you make those holes on the front window? They are so nicely arranged.

RURC
04-24-2005, 02:13 PM
In the end I did this...


Get the heat sink for the cm20 motors. Do not allow the temps to go above 200. The magnets will have serious problems. I repeat get a heatsink. I really like the fan mod. I feel the ducted shroud fan should also be implemented just for the "holly shit" factor.

jatetu
04-24-2005, 05:54 PM
SmoothHound, could you put some pictures of your car?? i too have a mamba and two thunder power lipos & would like to see how are yours allocated in the chassis.

thanks

Smoothound
04-24-2005, 06:03 PM
Jatetu

currently I'm using a 3s TP 1320 pack servo taped to the top of the old battery bay but it's temporary.

I will probably end up using either 3s or 2s TP 730's in the original battery bays in parallel. ie 3s2p or 2s2p giving me either 11.1v or 7.4v at 1460mAh.

TNB
04-24-2005, 11:01 PM
Smoothhound,
How long of run times are your getting? I thought about the fan idea, but after running on the 1/8th scale dirt track today, neither the motor nor the 3-cell LiPo were hot though my run times seemed to drop but I have yet to run it on the street again.

Here is a photo of the rear deck. I drilled it out to help keep the 3-cell LiPo cool which I have mounted with industrial strength velcro. The velcro near the motor is also layered. This keeps the LiPo level and raises it off the deck slightly.

http://www2.mini-zracer.com/albums/album623/H8_23_RearDeckHoles1.jpg

Smoothound
04-25-2005, 03:49 PM
TNB

Not really checked my runtimes yet, more worried about heat :rolleyes:


Good idea holes near the batterries, although I've only opened holes in the front screen. I thought too many holes underneath might let to many stones and dust in. This is also the reason why I have the fan blowing across the motor instead of sucking across it, I was worried it would pull crap from under the car :confused:

TNB
04-25-2005, 03:58 PM
Those holes would be under the stock receiver unit, not in the chassis. I also took that photo after running it on the 1/8th scale dirt track, so it didn't get a lot of dirt in there even after I flipped it end-to-end and cartwheeled it a few times. ;)

Smoothound
04-25-2005, 04:19 PM
Teach me to look at your pics properly next time :rolleyes:

plain_simple
04-25-2005, 06:52 PM
That looks awesome and looks like a good solution for sure :)

RURC
04-26-2005, 01:08 AM
In my plane stuff I have located a tiny NACA duct. 13mm x 10mm x 20mm. When my new cars arrive I am going to mount this above the motor just to see what it dose. The body fits rather tight but I believe it will fit fine. Any movement of air across the motor will be an improvement. With the hole where the fakey eng head is the air should have a nice escape flow across the motor then across the controller. The hole in the duct is 8mm. Remember a NACA duct works off the Bernuli effect and auctually sucks air into it providing you do not set it at too steep an angle. :D

TNB
04-26-2005, 05:42 AM
Remember a NACA duct works off the Bernuli effect and auctually sucks air into it providing you do not set it at too steep an angle. :D
Then what about using the eFlight 400 Outrunner--one of the LHS just got a bunch of them in. I noticed the KV rating was a lot lower than Castle's 8000kv motor, but it's my understanding the eFlight brushless motor has more torque and would stay cooler. Any input?

BitHed
04-26-2005, 07:15 AM
...i am beginning to like this eflight 400...I would love to know some more about it...

...Smoothound...yes nice arrangement of holes..did you measure them or just eyeball them up? Did you 'ream' them or use something else?

BitHed
04-26-2005, 07:20 AM
In my plane stuff I have located a tiny NACA duct. 13mm x 10mm x 20mm. The hole in the duct is 8mm. Remember a NACA duct works off the Bernuli effect and auctually sucks air into it providing you do not set it at too steep an angle. :D

...I didnt know any of this or have any idea what was happening SO...

...Apparently this is what a NACA Duct does; Stolen shamelessly from http://www.stockcarproducts.com/naca.htm

"NACA ducts are useful when air needs to be drawn into an area which isn't exposed to the direct air flow the scoop has access to. Quite often you will see NACA ducts along the sides of a car. The NACA duct takes advantage of the Boundary layer, a layer of slow moving air that "clings" to the bodywork of the car, especially where the bodywork flattens, or does not accelerate or decelerate the air flow. Areas like the roof and side body panels are good examples. The longer the roof or body panels, the thicker the layer becomes (a source of drag that grows as the layer thickens too). "

...and this is what one basically looks like...Sounds like a plan too...

http://img.photobucket.com/albums/v258/bithed/scoop3.jpg

Smoothound
04-26-2005, 08:01 AM
Bithead


Holes were reamed and eyeballed ;)

jatetu
04-26-2005, 08:39 AM
Then what about using the eFlight 400 Outrunner--one of the LHS just got a bunch of them in. I noticed the KV rating was a lot lower than Castle's 8000kv motor, but it's my understanding the eFlight brushless motor has more torque and would stay cooler. Any input?

May be, if you limit rpm on mamba 8000 (80 - 60% End Point Adjustment - EPA on the tx) yo too get mamba cooler.

OneTimeCRX
04-26-2005, 09:05 AM
... Remember a NACA duct works off the Bernuli effect and auctually sucks air into it providing you do not set it at too steep an angle. :D

Actually a NACA duct doesn't rely on the Bernoulli effect since this doesn't take into account the turbulence created. What happens is that the sharp edges of the duct create vortices that are directed into the duct. These vortices are of low pressure, which means that there is a low pressure inside the duct while the outside has a higher pressure. Air likes to go from high pressure to low pressure, so the air is then directed into the duct.

Use of a NACA duct so close to the ground and on such a small scale (as is the case with a RC car) might not be very effective since boundary layers are thick enough to interfere. Airplanes don't have as much of a problem since they're not close to the ground, but cars are definitely affected.

I've done windtunnel testing of scale model cars (from 1:10 to 1:4) including details of interior flows, and have found that the inlet holes will be pretty ineffective at this scale. What makes a big difference however is how big the outlet hole is. The bigger the outlet hole, the better. Especially if the outlet is directed to the low-pressure wake behind the vehicle.

BitHed
04-26-2005, 09:26 AM
Holes were reamed and eyeballed ;)

...AWW DOOOD!!! You SO have to rephrase that !! LOL...

jatetu
04-26-2005, 11:26 AM
Smoothound, now you have the fan, still have heat problems?

Smoothound
04-26-2005, 11:31 AM
I've had almost constant rain at the times I've been able to run so not tried it yet or been anywhere indoors with enough space...soon though. Plus I now have a new motor to try so it could end up going back in the M18 with the fan if I don't sell it :rolleyes:

Smoothound
04-26-2005, 01:53 PM
Smoothound, now you have the fan, still have heat problems?


Just been out and run it up and down the road at WOT and up until the point I cartwheeled and wrote off a shocktower it was running at around 150*F but ambient temps were colder than they have been, more testing needed once I find somewhere locally with some parts :confused:

BitHed
04-26-2005, 01:55 PM
...oops...doncha hate that !! I have alll this new stuff fitted and i find that NONE of my packs are holding a charge!!! WTF?!

...So Smooty how was it going until you went orbital? Oh DO tell :D

TNB
04-26-2005, 04:09 PM
May be, if you limit rpm on mamba 8000 (80 - 60% End Point Adjustment - EPA on the tx) yo too get mamba cooler.
That's not the point, the eFlight 400 Outrunner is a larger brushless motor and basically part of the case spins sucking in air to help cool the motor. In other words, more than just the shaft spins like it does on the Castle brushless motor. The shaft is also larger on the eFlight 400 Outrunner that it is on the Mamba package motors.

plain_simple
04-26-2005, 06:09 PM
i'm thinking about getting a Mamba for my brand new baby.. Which one do you sugest? the 8000? from what i read here it seems that getting a H8 cooked is not that hard but... :rolleyes:

P.S.: what pinions would u guys sugest for the 8000 mamba?

lukeita
04-26-2005, 10:33 PM
I asked the same question... I think 8000 is too powerful for H8: you'd better to chose 6800 (as suggested by CastleCreation) or 5400 (as suggested by some friends in this forum), maybe 5400 will give you more torque and less top speed
bye

plain_simple
04-27-2005, 11:16 AM
ok.. thanks for the advise :) will try to get both of them and see which one is the best bet :D

paulj2
04-27-2005, 10:41 PM
Plain simple,


ok.. thanks for the advise :) will try to get both of them and see which one is the best bet :D

If you haven't ordered the 8000 yet, I would sell you just the motor. I need the esc and you could use the esc from the 6800 0r 5400...they use the same esc.

Let me know, Paul

paulj3@msn.com

vindictor67
04-28-2005, 02:38 AM
i'm thinking about getting a Mamba for my brand new baby.. Which one do you sugest? the 8000? from what i read here it seems that getting a H8 cooked is not that hard but... :rolleyes:

P.S.: what pinions would u guys sugest for the 8000 mamba?


Holy Sh*t, just finished installing a Mamba 6800 and HS-85MG servo. Now that is the way this thing is suppose to run! :D Smokin' and actually steers in both directions. Ever been around a "run-away" nitro buggy. The tires grow to 2 or 3 times the diameter due to centrifugal force. The 6800 does that to the tires on the H8 when holding it up. :eek: I'm using an 11T pinion for the associated 18T. Haven't really been able to run it hard yet so I'm not sure about any heat issues. I installed a nice blue heat sink from Helihobby so shouldn't be a problem. Oil boingers are definatly NECESSARY at these speeds!

plain_simple
04-28-2005, 09:35 AM
Ok, it seems that the 6800 is really the way to go. I'm already expecting one of those green nice things. Will let u all know how it goes when i'm done... about the 11th it looks like it gives more torque which seems to be a problem with the 8000 motor. Did u run it on dirt? If u did can u tell me how does it feels on that kind of surface?

quikslvr
04-28-2005, 12:34 PM
I have a 6800 in my buggy with a 13 pinion. I works really good. I had it out on our track big offroad track last night and it ran great, at least until the bottom screw on one of the front knuckles fell out (insert swear words). The motor, battery and ESC temps were not smoking hot. I may drop down to a 12 to get a little more acceleration, but I need to scuff the slipper a little more, it is still slipping.

Anyone know what part I have to order to get a new screw for the front knuckle? Hey Bit, can you hook me up? I know you were having the same problem.

BitHed
04-28-2005, 12:57 PM
...Quik mate there is good news and there is bad news...well isnt there always :rolleyes:

...The silver screw that fell out is a 3x7 self tapping screw that doesnt actually exist in the RC world...Think of it as a KYOSHO quirk :mad:

...The good news is that you can probably find one in your LHS (read: Local HARDWARE Store) better than you could find one at your LHS...The hobby one...

...We are figuring KYOSHO will have put them into the 'screw set'...WHY? Because if you dont have a 'set' then you are 'screwed'...eww...im on a roll tonight :D You COULD try a 3x6 from elsewhere on the chassis or you COULD try a filed down 3x8...I had some joy with a 3x6 shoved in with violence :) But is probably not going to last...

OneTimeCRX
04-28-2005, 12:58 PM
I've had a screw fall out too. I replaced it with a spare screw normally used for computers. It fit in there perfectly. Now, in order to catch the screws when they fall out (and it's almost guaranteed they'll fall out again) I've put some tape underneath the screw to catch it. This will hopefully hold out until I get the alloy knuckles.

vindictor67
04-28-2005, 01:57 PM
Thanks for the update on what to look for guys. I'm going to pull mine out and apply some thin ca. Will act like locktite for plastic. Will let you know if it helps.

Also broke out the H8 at work this morning to show off. And show off it DID!! :D This thing just screems!!! It will actually SMOKE the tires on concrete :eek: but still has a smooth enough throttle response to take off in very loose blow sand.

ME LIKEEE

plain_simple
04-28-2005, 02:12 PM
Plain simple,



If you haven't ordered the 8000 yet, I would sell you just the motor. I need the esc and you could use the esc from the 6800 0r 5400...they use the same esc.

Let me know, Paul

paulj3@msn.com

u got mail Paul... let me know whats the best way for us to do so.. i can always use it on my touring car so it might work out for both of us ;)

paulj2
04-28-2005, 06:10 PM
I answered you through e-mail.

Thanks, Paul

plain_simple
04-28-2005, 06:45 PM
ok.. you already have an answer too

quikslvr
04-28-2005, 07:00 PM
...Quik mate there is good news and there is bad news...well isnt there always :rolleyes:

...The silver screw that fell out is a 3x7 self tapping screw that doesnt actually exist in the RC world...Think of it as a KYOSHO quirk :mad:

...The good news is that you can probably find one in your LHS (read: Local HARDWARE Store) better than you could find one at your LHS...The hobby one...

...We are figuring KYOSHO will have put them into the 'screw set'...WHY? Because if you dont have a 'set' then you are 'screwed'...eww...im on a roll tonight :D You COULD try a 3x6 from elsewhere on the chassis or you COULD try a filed down 3x8...I had some joy with a 3x6 shoved in with violence :) But is probably not going to last...

Bit, thanks for the info. I assume that the little plastic collar on the silver screw isn't anything to worry about. I have already employed a little duct tape to keep from loosing screws in the future.

Any time frame on the alloy knuclkes? They are much needed. The front end seems very sloppy (as on every other mini rtr). Sorry, this is a topic tangent.

TNB
04-29-2005, 07:01 AM
It's time for a change, so my 8000kv motor will be coming out soon. It is not that I got it too hot or anything, it's just that I am going to test a couple of AON brushless motors.

http://www2.mini-zracer.com/albums/album623/H8_NewBL1.jpg

TNB
05-01-2005, 10:49 PM
I moved the photo and see what happens since I can't edit the post. :mad:

http://www2.mini-zracer.com/albums/album649/H8_NewBL1.jpg