Doing my Homework for Twin Mamba Monster flux.
 

Ive decided to build a second racer carbon flux and have written my shopping list up for that........

But i do not want my DB-17 chassis to go to waste as i really like the stability it gives..... and so decided why not go a little crazy... and make it REALLLLLY FASSST :surprised:

I have seen a few twin motor maxxs and revos and custom stuff... But not a savage yet... I know a better idea would be to run a huge single motor on 10s but i prefer this idea. I just want people to point out potential problems i could run into and decent items that would work for me :yes:

I dont feel much would need to be done apart from finding a new twin motor mount (similar to the e savage, i guess) and then just moving around a few servos and adding battery boxes to the side... Oh and obviously the 2 motors and 2 Escs...

There is going to be a bit of custom work done but should be fun...

I dont know much about twin mounts that were used on the E-savage but can they house the neu 1515 2200kv motor???? I would never jump this thing, being afraid that the motors would be stripped from their mounts.

Now... apart from sourcing an appropriate motor mount what other potential problems do you think i could run into for ex... tranny probs?????

Some of you may think this is a stupid project but its not going to be my main savage... i just want to push the savage and see how far it could go :)

I know that a few people have pushed the savage to 80mph but that is with heating problems. So this is why i thought... If i share the weight over 2 motors... i should run even faster and maintain cooler temps...

I know this is the best place to come regarding motors so give me your advice!!!! I dont care if its good or bad... just lay it on me!

THANKS!

Ive been speaking to dan at kershaw and he has offered to make me a custom mount. I have had to change my mounting ideas... and mount one motor on top of the other.

here are some pics i sent to dan, so he can get an idea of what needs to be done for the custom mount... I also asked him about possible interference of two motors and magnetic fields...??? any one got any input on this

http://i878.photobucket.com/albums/a...7/DSC00274.jpg

http://i878.photobucket.com/albums/a...7/DSC00273.jpg

Maybe...you should consider, or at least look at, a belt drive with that. Dont know where the heck you'd source a belt in the correct length.

I see no problems with interference. There have been many dual BL's done. The issue become synchronizing them so that they are working together and in unison, not fighting each other.

I'd suggest getting a 1521/1Y and pumping 8s-10s through for some super high speeds runs. Dual brushless isn't always the fastest... but looks cool! :lol:

what is the 1521 rated at kv wise... how many s can it handle and what sort of esc would be needed?

1521 1Y is 1580kV, like the CC-neu 1520. It can handle 60 000 RPMS and a lot of power, so you just need a high voltage ESC to run it at your insane speeds :D :D :D
7 or 8S with the 1521 1Y should give you plenty of speed.
Keep in mind that many people use the 2200kV on 6S, you can as weel us the 1521 1Y on 8S with the same motor RPM, but a lot lot lot more TORQUE :D :D :D:lol:

damn i should have bouught that motor from the beginning! looks like it may even be able to handle up to 9s if it can handle 60,000rpm! Still curious as to what kind of escs these use as this is out of my knowledge teritory...

Well if you had mechanical braking... Alot of HV users use the Castle Creation 110HV or even a HV140. But again you would need mech. brakes.

http://www.castlecreations.com/produ...hv_series.html
or even something from HobbyCity
http://www.hobbyking.com/hobbycity/s...dProduct=10332

I use mechanical brakes... motor brakes are rubbish for feel when driving.

Could i even use these ESC with my current 1520??? couldnt a 1520 be able to handle up to 8s??? or is that too much???

thanks for the links zippy!!!! they are some impressive speed controllers!

1520 is limited to 60k rpms, so whatever voltage doesnt put you over that is ( in principle ) fine- not exactly a daily driver kind of setup though, wouldnt really be ideal for offroading at ~70mph for example ( whicj is why speed runs are done onroad, not off ). I figure a lighter weight CF flux would be fine offroad with the MMM system & sensible speeds, then turn the original heavy weight version into the road missle with a single massive motor ( or dual motors if you really wanted to ) & HV esc. The heavier weight would be better for getting good traction & keeping the front end down- most guys have issues with lighter weight speed machines as the wind lifts the front end at higher speeds, so have to resort to front wings and such. Heavier weight would place a bit more load on the electronics, but if the motor/esc/lipos are upto task, then it shouldnt be an issue really ( just takes a little longer to reach max velocity ).

Are they going to run in sync with eachother and what about voltagewise what lipos

The syncing thing is easy enough, just short two motor wires with a single sub-c cell to align the rotor to a certain posistion, repeat for the other motor ( same wires ), then mount the motors & pinions + mesh to the spur without rotating the shafts before they are meshed. Once meshed, they will stay synced until one motor is un meshed and the shaft rotated freely of the other motor.

neil thanks for the help... I didnt know the motor was capable of 60000rpm...
If that is the case, my current gearing which is:

Differential Ratio: 3.2222222222222223
Transmission Ratio: 1.5366847826086956
Other Ratio: 1
Spur Tooth Count: 47
Pinion Tooth Count: 17
Total Voltage: 25.2 - rated at 4.2V per cell when fully charged.
Motor KV: 1600
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0.5
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.76 : 1
Total Ratio: 13.68955 : 1
Tire Circumference (inches): 20.42 inches (518.68 mm)
Rollout: 1.49:1
Total Motor Speed: 40320 RPM NO WHERE NEAR 60,000rpm!!!
Vehicle Speed: 56.95 mph (91.49 km/h)
Effective KV Value: 1600
KT constant: 0.85 oz-in/A

This is on 6s rated at 4.2v not 3.7v... and what i would be running most of the time.... only 40000rpm!!!!!
You say that this motor is rated to 600000 so theoretically with a better speed controller i could run 8s for road use as not to cause the motor or esc any harm... Is this really possible???

This is the same gearing but on 8s


Differential Ratio: 3.2222222222222223
Transmission Ratio: 1.5366847826086956
Other Ratio: 1
Spur Tooth Count: 47
Pinion Tooth Count: 17
Total Voltage: 33.6 - 8s rated at 4.2V per cell
Motor KV: 1600
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0.5
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.76 : 1
Total Ratio: 13.68955 : 1
Tire Circumference (inches): 20.42 inches (518.68 mm)
Rollout: 1.49:1
Total Motor Speed: 53760 RPM - still well below the 60,000 rpm mark!
Vehicle Speed: 75.94 mph (121.99 km/h) - I WOULD BE HAPPY WITH THIS FOR ROAD USE!
Effective KV Value: 1600
KT constant: 0.85 oz-in/A

If this is correct... i doubt i would need to start building a twin motor savage or increasing motor size!!! This would make me happy as i would rarely run 8s, but knowing i can makes me happy lol just need an appropriate HV ESC.

please confirm this neil before i get too excited

You don't need to go to the motor limit, keep in mind that the efficiency of the motor will be poor at 60 000 RPMs, so 8S will be plenty and will give you a safety gap between your RPM and motor RPM limit.
All you need now is if you have already a 1520 two 4S batteries and a HV ESC :D

OH YES YES YES! Nuz... Just the response i wanted to hear!
i was under the impression that this motor was only good for 6s!!! (dont know why)
Of course i dont want to hit the motors limit... But considering when i was using my 1515 2200kv motor on 6s... it was at 57000rpm and was doing fine... This motor on 8s is more efficient than the 2200 on 6s as its only spinning 53000rpm!

Now my next question is regarding choosing and appropriate HV ESC...

Now considering the MMM is rated at 120amps continous... I would need something that matches that or higher to run safely correct???
Does that mean that the HV-110 is not adequate and i would be forced to go for the HV-140???

What are the main difference between these two ESC???
Phoenix HV-140 = $359.00
Phoenix ICE HV-160 = $320

Same max voltage yet the cheaper ICE is rated to handle more amps.
Whats the main difference... And what do people recommend?

THANKS!

The motor eats the amp he need ! that mean big load = big current, and big truck, big gearing = big load.
Maybe the ICE is less efficient than the HV ?

why do you say its less efficient? Wouldnt it be better considering it can handle higher amps???

Maybe electronical architecture is different... Or maybe you can program more parameter in the HV 140 ?

i will do some searching into it.. .At least i know what i need to do now... May need to look at alternative gearing again going to 8s... but i will see...
Thanks nuz and neil!!

The Neu/Castle 1520 should be able to handle 10s no prob. Same difference as running 6s on the Neu/Castle 1512 2650kv but on a larger can.

Correct. If you are trying to run high speed runs, making 1 or 2 passes at a time, then these motors can take the abuse at the RPM limit and even over the limit.

Keep in mind Nic Case ran a 1521/1Y on 12s powered by a Phoenix HV110 in his world record run. That was also a single pass, not on or off road bashing.

Any continuous usage, I would recommend staying around the 40-45k rpm MAX.

I would go for the ICE HV-160 if you can. The added amperage and the data logging abilities are quite nice.

Yup, this is based on speed runs only. I will be running a Neu 1518 1.5Y on 12s and will probably eventually bump up to the 1521/1Y or the Castle/Neu 1520 equivalent. Shooting for some kind of record :wink:

Ok a few things... need a little advice and confirmation...
As you know iam going to try an 8s configuration... to keep things balanced, in the truck,
I am going to buy 2x2s and one 4s lipo. And place the 4s in the centre of the chassis and the 2x2s either side in battery boxes by kershaw.... I will be using bullets and was wondering if it is ok to connect them this way...

http://i878.photobucket.com/albums/a...agrambatts.jpg


Also im not sure if im going for the HV any longer as i am a little worried it will over heat as it will not get the same air flow like it would on a plane... Or is this not the case..???

This was brought to my attention and the ESC in the link below has a built in fan which should be more suitable right?

http://mgm-compro.com/index.php?tid=...-boat-z-series
http://mgm-compro.com/pics/s-z-series-fan-types.png

Does anyone have any experience with this item or no much about it???
THANKS

The wiring diagram you posted is correct, as it keeps everything in series. As far as the ESC, if it doesn't have a fan, add one. There have been other users here using the castle (and other manufacturers) airplane esc's in ground vehicles before. Sometimes with a fan, sometimes not

When you do your calculations it is better to use ~3.7V for the cell voltages. Under load they won't be holding at 4.2V/cell even when fully charged.

^Ditto.

MGMs are great escs, reported to be very smooth, but they are ( arguably ) way overpriced and a frickin' nightmare to programme correctly, even with all the extra cables that are required. I'd say stick to a boat/ plane esc and mechanical brakes, or have patience and wait for Castle's new 1/5 scale car esc. Otherwise, look into the Kontronic Jazz and Jive escs perhaps- even Lutach might have something suitable in the way of HV escs...

^ there's always schulze too.

Curious as to synching two motors though. With two esc's is it necessary?Because it's really two separate systems driving the same spur, as long as the settings are the same I can't see them fighting each other. I mean once spinning a little the esc's know their motors position from the emf feedback, regardless of one motors position to the other. I tried a dual vxl setup on a erevo without synching and had no problems.

i dont use a fan on my hv110, in a truck it gets alot more air than it would in a plane.

the hv110 runs alot cooler than the MMM does in my revo

A suitable Schulze esc would cost a pretty penny I bet..

You're right about the syncing issue though, it isnt required as such, its just a nice idea really.