Twin Force Brushless Questions

Hi All!

I am a new rc enthusiast and this is my first vehicle.

I have a Twin Force and want to set it up with a brushless motor, ESC, servo, and Radio.

I have already decided to get some gp3300 6 cell packs so I will be running this on 12 cells for now.

I am looking for the decent speed right now, with good runtimes as I learn to drive this truck with the stock parts, and also the ability to go much faster later once I upgrade parts and run more cells.

What motor and esc do you recommend, and how much speed and runtime can I expect?

I have been looking at the Feigao motors as they are pretty cheap, but I dont understand the differences between the different numbers, 8L, 9L, 10L, 7xl??

I'm considering getting the Hitec 645 high torque servo and the Airtronics MX3 radio, good idea?, better options?

[Gustav]

Welcome Golfmonke!
The 9L with the 9920 controller seems to be a popular choice for 12 cells.I'm new here too and don't pretend to be an expert on brushless but Mike will keep you right.

Getting the gearing right is vital with any brushless set up so see what spurs you have or can use with the twin force and also maybe the diff ratio and mike can probably recommend pinions for you.

[Batfish]

The Hitec 645 and the MX-3 radio are fine parts for someone starting out. If you plan on moving into racing at some point, you may end up with a stronger/faster servo and a radio with more options, but there's absolutely no need to go that far when you're starting out.
The only suggestion I'd make in regards to the radio would be to consider stepping up to a synthesized radio like the MX-3S or similar radio. If you're just bashing and have noone in the area that runs R/C land vehicles, you may be safe with only one frequency, but I think it's always a great idea to have more than one available.

[Gustav]

Oh yeah,make sure you get the RC-Monster motor clamp/heat sink if you get a Feigo motor.It prevents the end bell from popping off on pressed end bell type motors and looks cool.

As for radio gear,i've been using JR stuff for a while now and can recommend the XS3 or the 2 channel version if you only need 2 channels.They have plenty of adjustments like end-point adjustment,exponential,dual steering rate,channel mixing,multi model memory and stuff and have synthesised versions.

I've been using JR z8800T servos for steering which is a digital servo with about 188 oz/in of torque and i think is around $100.
For a cheaper option i can recommend the JR 650M which i think has 144 oz/in and is around $50 and i think Mike stocks them.

[squeeforever]

well for good runtimes i would recommend a lehner but a feigao would be a good choice. although if you were to get a feigao i would get a heatsink from mike to keep the can from popping. also would mike want to consider getting some ibc cells. they have a lower internal resistance and higher mah. there are offered in 3600 and 3800 mah and are said to get the best. im not to familiar with the twin forces but i would say a 9l would most likely be a good choice depending on the weight and a warrior 9920 is definately the way to go. also, i woul say the mx3 would get the best radio for the money but i would get the blue bird 630mg. i have one and really like it. not only for the low price but for the specs. im not sure about the gearing but if you could tell us what the gear ratio is in the tranny we might could help you.

[Gustav]

i've found the twinForce gear ratio quoted as 21.71:1 compared to 28.9:1 (1st), 17.9:1(2nd) for the e-maxx.

i don't know if that includes the diffs and spur and pinion or not but someone here may know.

Any way if it doesn't then i think you could work it out like this:
a popular ratio to use with an e-maxx 2nd gear is around 15/51 which is 3.4:1 so if the diff ratio is similar to an e-maxx then divide the no. of teeth on your spur by 3.4 to give you the no. of teeth for your pinion.Then maybe go up a couple of teeth on your pinion as your tranny is geared slightly lower than an e-maxx 2nd gear.

Someone more knowledgeable than me should check this out first as i am rubbish at this.

I suppose a better way is to count the no. of teeth in the centre tranny and on the diff ring and pinion gears to get the ratio making this entire reply pointless.........oh well never mind:rolleyes: .

[Gustav]

Scrub that last transmission.
for an e-maxx 2nd gear with a 9L/9920 on 12 cells it looks like a better starting point for the spur/pinion ratio is more like 4:1

Have you seen Promod's twin force projecthttp://www.rc-monster.com/forum/show...=&threadid=754

Thanks for the help! Didn't expect to see 6 replies so fast!

squeeforever recommended a lehner motor for better runtimes, why is this? How much more of a runtime could I expect? I dont mind spending a little extra if it's worth it?

Ok, most of you recommended the Warrior 9920 for the controller, I have also seen the Schulze 18.97 that is about $120 more but it looks like close to the same specs, is it better than the Warrior?

I have seen the IBC 3800 and was interested in getting 6 cell unmatched packs, I couldn't find them on this site, do they sell them here?

Why do all of the Radios come with a servo? Do they sell them without the servo?

I dont understand all of those gear ratio #'s

:C:

[Gustav]

Yeah don't worry about the ratios.Sorry I was just having a go at figuring it out and then realised i couldn't.confused myself.

The 9920 is the one to go for.The Schulze is to be avoided by all accounts.they have a tendency to go up in smoke and shulze never honor the warranties.i actually have one unused which i would try to sell you if i was that way inclined.

Mike should chime in soon and basically you should go with what he recommends.

As for selecting a suitable pinion to start with just count the no. of teeth in the centre transmission.I think it's just a sprocket with a chain to another sprocket on the Twin force isn't it so just count the teeth on the sprockets and of any spur gears you have or can use with the truck and Mike or someone else may suggest suitable pinions from that.(sorry if you already know but pinion is the little gear on the motor and spur is the big gear that it spins)

Radios mostly come with a basic servo but usually aren't up to steering a monster truck.An extra $50 will get you a decent servo.

Hmmm, I just read an article about a guy who setup a brushless lipo emaxx that gets 45 minutes of runtime!!

He was running a Lehner 1600 and 2 11.1 v 4400mah lipo packs for ~24 volts. (using a Warrior 9920 esc as well )

This is something I might consider as i'd have to buy 3-4 sets of NiMH to get that much runtime. I checked some Lipoly packs and found some 6300mah 11.1 packs for $169. So that would be $340 and 3 sets of NiMH would run me about the same no? I'd also be creaping up on 1 hour of runtime I would assume? Hmmmm....

I wonder what kind of speed he was getting, not that I need a lot of speed. I plan on using this for bashing, don't plan on getting into racing.

[squeeforever]

well if you look hard enough you can find the mx-3 without any servos. also, i recommended the lehner because it has a higher efficiency and better torque than a comperable feigao. also, if you dont plan on racing i wouldnt get lipos. i would just stick with nimh. the lipos would take for ever to charge.

Ok, i've decided to try and set my truck up for maximum runtime and 30-40mph.

So I will copy this guy here who setup a lipomaxx :)
http://www.kmcsonline.com/casemod/emaxx/
(He may be a member here?, remember seeing the name )

He is running a lehner basic 1600xl, warrior 9920 and 6s lipo cells.( ~24 v)

I was wondering if stepping up to a lehner 19xx or 22xx would help me increase my runtime even further. I had read an article where somebody said that these motors will run at lower amps for the same power output.

Do you think this is worth it, or just stick with the 1600?

Either way i'll be getting the following:
Airtronics MX3 Radio
Hitec 645 or JR650 servo
Warrior 9920
(3s2p LiPoly 4200 or 6300mah) x 2 for ~24v
AstroFlight 109 charger

Nevermind, answered my own question, gonna get the Lehner 1600 as I can just buy another pair of batteries for the extra price that the 19xx or 22xx lehner would cost anyway :)

Now I'm just waiting for the Warrior 9920 to come back in stock :W: