What is the best setup 8xl and warrior 9920
 

Hey guys. I just ordered a 8xl motor and warrior 9920 for my E-Maxx. I'm planning on running 20/66 gears at first and might adjust from there. I have 2 7 cell 4200mah batteries for it already. The write up on the controller says it will handle 20 cells so I'm tempted to add another 6 cell pack on. I'm just looking for a sick truck that can wheelie all the way down the street and has a great top end too. My question is will this set up handle 20 cells or should I stick with 14? And does anyone know what kind of performance I might be looking at with either set up? The rear end will keep the stock ratio for now since I just got finished building up both diffs.

it can handle the extra 6 cells no problem and the power would be awesome on 20 cells.

you will definately have some trouble keeping it on its all 4 wheels and it will probably end up on its roof some too

8xl on 14 cells=:)
8xl on 20 cells=:eek:

i agree that would be very scary and fast on 20 cells :eek: :eek: :eek:

When it was stock with 14 cells it would flip on command even in 2nd grear. Then I got a custom wheelie bar off ebay and would do wheelies for about 15 - 20 ft..... 3 times till the rear driveshft exploded! now I've beefed up the truck to take some power. A guy at work wants to race me with his little gas road car and I wanna stomp on him! LOL And if I can't I'm deffinately gonna drive right over his car. But anyways.....

I decided to change to the strobe clutch with mod 1 gears. Does 16/51 seem like a good setup or do you think I should go to 18/51? This will be my first bl setup and I don't know what kind of torque I will have with this. I was actually thinking of getting a HV-Maxx till I found this site and started reading all I could. All you guys talked me into something much better and didn't even know it!

I'm running 14/51 with a 9L and I should have went 15/51. I have a 7XL come right now. I'l be going 16 cells with 16or18/51 to start with. I think the 8XL should easily go 16-18/51.

14cells + 8XL = 40mph and big wheelies
20cells +8XL = 50+mph no problem and uncontrollable wheelies (you will need a steady finger, or lower the truck a lot).

Would be great on 16 cells. Great power and runtimes.

See that's the type of power I'm looking for. Sick power. Where people see it go and say "what the ....:eek: ". I just use it for fun bashing outside, I don't race with it so the wheelies are fine with me.

Let me ask one thing though, when it comes to the gearing, does anyone know how much of a change in top end 2 teeth up or down on the pinion makes? 2-3 mph? More? Less? I'm hoping 16/51 gearing will be right on the money cause I hate having to order parts and then wait a week to try it out. I just have no idea how much torque the 8xl will make on 20 cells. How would it compare to titians on 14 or the HV-Maxx?

I would guess a change in gearing would make a big difference with this set-up, both speed and temp wisee. You will have to watch controller temps with that motor on 20cells. I would think 16/51 would be a good starting point for this set-up, although someone else might correct me.

There will be ABSOLUTELY no comparison between an 8XL on 20 cells, and titans/HV-maxx on 14 cells. I hope you've got a strong driveline!

I hope the drivetrain will be ok. Will have strobe slipper, flm tranny case + idler gears, carbon steel driveshafts and axles, integy diff cases with flm diff cups and 3 mm screws, airtronics 94358Z steering servo, traxxas big bore shocks with team blue star progressive rate springs, aluminum custom wheelie bar, and rubber sealed bearing replacing all the stock ones everywhere. I left the rest of the truck stock as it seems pretty tough and light.

I do question if the rear diffs will hold up under prolonged use though..... anyone have any experience with a set up like this and breakage problems?:confused:

You CANNOT compare 20cells and a 8XL to a HV-Maxx. I run 14cells with a 7XL and the power is crazy already. Too much wheelies, just a shame with little speed.

I doubt the 8XL will have long runtimes on 20cells though. :(

Hey Nick, do you think 18 cells would be better than 20? I really don't feel like cooking $300 worth of parts by giving too much power. I'm gonna use 4200mah batteries so I was hoping for around 15 mins of runtime at least. The way I'm gonna set it up I can run 14 cells or 20. Does run time go way down the more cells you put on? I would have thought it was the other way around given a proper gear ratio. If the torque is too much I should just be able to get a larger pinion to compensate correct? I ordered 16 and 18t pinions with the 51t spur. Could always go higher as long as the electronics don't cook right? mmdooley, you will have to let me know how it goes on yours.

Maybe Mike can give me his input on this setup???? I think I need it.

well 20 cells would be just fine. just watch temps like maxxdude said. and if geared right you shouldnt loose runtime. also, 15 minutes with ib 4200s is easily obtainable.

Hey guys, check out this chart I found. You just plug in your setup and it charts what your performance should be. Pretty cool.

http://www.qcda.com/emaxx/speedchart.asp

If you increase the number of cells, the motor will draw more current (ie. shorter run times). In other words voltage is proportional to current. Another interesting fact is if you double voltage, power will quadruple: So adding an extra 6 cells will almost double power.

i dont think thats to acurate.....

I just set up my 8xl & 9920 w/ 12 IB 4200s. It is really fast!! I will be fine with 12 for a while - I will probably increase some time down the road. If you have any weak points in your build, this setup will find them!

maxxdude;

Current is opposite proportional to voltage.

With 6 cells more on 12 cells, you won't double the power either. It will be 50% more.With more cells, comes more runtime as well, if you keep running on the same speed as with the lower amount of cells.

Serum, let me show you some formulas:

V=IR ; potential difference (voltage drop) = current x resistance (a constant)

Hence voltage is directly proportional to current.

P=VI ; power (watts) = current x voltage

If we re-arrange the first formula to give ; I=V/R , and substitute this into the second forumula we get;

P = V x V/R or P = V^2R .

Again say R is a constant, if voltage doubles, power will quadruple. This happens because as V doubles, I doubles, and P=VI, so P quadruples.


So if 18 cells are used rather than 12, this will give a ratio of 1.5:1.

1.5 x 1.5 = 2.25, so theoretically power will increase by 125%.

Hope this clears things up


*PS. To answer your last thing, adding more cells will decrease runtime, because more voltage = more current. This can be combated by a higher turn motor that will draw less current at a given voltage (in other words its resistance is higher), however the sacrifice will be power.
In theory a 7XL on 20cells will be more powerful than a 12XL on 20cells. OF course all this is providing the batteries can provide the current.

I am sorry, but 12 cells can do 1200 watts and 18 cells can do 1800 watts. (that's no 100% boost, but 50)

And if you need 1200 watts on 12 volts, it is 100A and on 18volts that is 66.67A, (P=U.I) and like i said, if you use the same power, runtime WILL be larger, not smaller. Adding cells gives you more energy, so runtime will increase. I know this law of Ohm, but in this, you forget a few things, the cells can deliver a maxximum amount of power each. this will not increase if you add an extra cell.

That is quite true, and why I said at the end of my post, that it all depends on whether the batteries can supply the power.

That is incorrect, if you increase voltage you increase current - its proven scientific fact. Its not a matter of 'if you need 1200watts', motors do not work like that. I could spend hours explaining why, but its a Sunday and I can't be bothered.

I'm happy to agree to disagree :)

I won't mind clearing one thing up; (even though it's sunday)

from the beginning i stated 'if the same power is needed' (with that i meant the power on the wheels) so, knowing this, you simlple have to admit that a larger number of cells will give you MORE runtime (not to mention the setups efficiency will increase on a higher voltage)

If you want to run 50 mph on 12 cells, your batteries will be empty FASTER than with 18 cells going 50 mph. Got it?

You have got your theory right, but you need to translate it back to the limitations of RC, (which includes the fact that the batteries simple don't do a 225 percent increase going from going from 12 to 18) Power isn't unlimited in these, so you are not right if you say that 6 cells will add 125% of power. It just isn't right period.

My goal was to disagree with that, open your eyes and see.. ;)

No worries though, i still can drink a beer or two in the pub with you... :p (as long the beer is not hand warm...)

Fair play :dft003:

I take it that when you say you running a higher voltage you also mean a higher turn motor. I think thats what I didnt quite realise. I thought you meant on the same motor.

LOL..

Brushless motors do work like that..

Charming thing this Brushless is...Actually i did meant on the same motor... like i said, if you need a certain amount of power to go 50 mph, the amount of power to go 50 mph on more cells will be the same, so with that, you get more runtime.. (you don't need to use the entire power range)

Have a good sunday buddy!

I think we are both thinking on two different wavelengths. What I said is correct on a scientific scale, but what you have said is more on the practical scale - and hence more appropriate for rc's. There is no denying that, providing everything else remains constant (gearing, amount of throttle applied, temperature) a motor will draw more current at a higher voltage than at a lower voltage.
The beauty of running at higher voltages is you can gear down, and therefore reduce the amount of current the motor will need to draw - which is effectively what you said, and I fully agree with.

Good talking with you Serum, and I hope we have reached an agreement.

Yeah, sure.. We are not too stubern to see eachothers right.. ;) And heck.. It is a nice sunday..

What's up with that smiley flapping his tongue out?!

:032:

Nevermind that! Whats with this one: :020:

...lol.

Your smiley has got a bad infection on his ear if you ask me..

i think that we are getting a little off topic here

According to the Ohms laws as I understand them, voltage and current have a inverse relationship given the same load. As voltage goes up current goes down and vice versa. So if I use a certian motor and gear ratio with 14v it will draw more current then if I use 18 or 24v. But if I change the load value by changing the gear ratio causing the motor to work harder then then current draw will increase. Can anyone back this up? Lets put this issue to bed. LOL

I think if I gear it properly I can get about the same run time on 20 cells as I do on 14. I just have no idea what ratio to use.

Maxxdude and Serum - nice discussion and I am glad on this fine Sunday that we worked it all out in such a friendly manner. :)
To summarize.....Maxxdude is 100% correct on the "laws". If you take the same setup and simply add voltage, the amp draw will increase proportionally as well and therefore increase total power and decrease runtime(within battery limits, of course). For our purposes, though, the "identical" setup is seldom used when we add voltage(nor should it be). When we add voltage, but change the gearing to achieve the same speed, runtime will surely increase, even with the same motor. If the motor is changed to accomodate the higher voltage, runtime AND speed can easily be increased(hence the purpose of selecting an appropriate motor for the application to maximize power, speed and runtime). Basically, you are both right!
:)

Ok Mike. So what would you think would be the proper gearing for this setup for 14cells? 20 cells?

What slipper setup? Strobe? stock diff(which will fail on 20 cells in time, even with the aluminum cups and cases-though they will hold up for a while if you are just running on the street)?
20/51 would get you around 40mph. Runtime wouldn't be spectacular, though.
On 20 cells with the Strobe and 16/51 gearing, speed would be in the mid 40s with stupid torque and a pretty decent runtime as well. 18/51 would get you to 50+ mph if the cells can deliver the voltage.
Given your lack of brushless "drive time". I think you will be quite overwhelmed with the power of this setup on 20 cells. Your wheelie bar won't stop the truck from flipping onto its back with this power, and the torque will be pretty extreme. I think it is safe to say you will be blown away with the performance(and so will anyone that is watching). You will want the suspension, steering and overall setup to be on the money or driving will be a real problem!

WOO HOO!!! Glad to hear that Mike. That is what I'm looking for. Stupid power! I ordered the probe clutch with 16t and 18t pinions from you this weekend.......along with a ton or other parts. I did build up the rears already, aluminum diff cases and cups with 3mm screws. The problem I see with longevity with these diffs is the lubrication problem. Any grease put on the gears during assembly will be whipped off when the truck is run. I'm tempted to silicone the cases together and add 1/2 oz. of 70wt gear lube in it. Do you think that would work?

The diffs could easily be modified to accept regular viscous fluid if you have access to a lathe. This would be a better option IMO. Also, the Revo diffs could be used with a different bearing on one side(Revo diff cup is a little different), so a Modified Revo diff(aluminum diff cup) would probably hold up better. Both are band aids in the long run, though. 20 cells and an 8xl motor will NEEEEEED 1/8 diffs for ultimate durability.

You're right. But at the moment you show them as out of stock. So I will probably just run it with what I have for now, till they go bad, then get the better diffs. What would I need to change my pinion to with the bigger diffs if I was using a 16t or 18t with the stock ones?

And also, just wanted to say what a great site you have here. I got so much info from this forum that I was saved from buying a HV-Maxx and being dissapointed with the power. And your store has just about everything I need or want. Great job.