Gearing an ERBE for racing on 4s
 

Hey guys, I'm trying to finish getting my ERBE ready for next season, Only real drivetrain mods I've made are a Tekin 2250 kV motor and AKA city block truggy tires. I'm trying to decide gearing, but the calculator I've seen say that I'd need to run like a 20/54 or 22/54 to get up near 40mph. This just sounds WAY too high! I was curious what the people on here that are racing on 4S run on their ERBEs.

Whats the diameter of those tires?

Educated guess:

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

68/24 should be good for just shy of 40mph, perfect for racing. Just make sure you have good lipos really.

I plan to use TP 5000mAh 40C lipos, so lipo quality should be fine. That's the calculator I used, but was struggling a bit with. Tires are 5.6 I believe.

I always found you need to inflate the size of the tires a bit to get an accurate (vs radar) speed reading. I'd aim for an FDR of ~13:1

Cool, no lipo worries then. With 5.6" tires that gearing is still good for ~37mph, and thats without factoring in any ballooning, so I'd say either run with 24/68, or maybe 24/65 to bring it back upto ~40mph.

Yeah, I need to play with it a bit tonight, I want to runn smaller spurs to help move the motor down, etc. So if I run the same ratio that works on a 68 or 65 tooth spur on a 54T spur I should end up around where I want to be. Compared to the first set you sent me, a 19t pinion and 54t spur should yield the same numbers. I'll have to play with it more. I was kind of looking for the "easy answer" with someone who ran an ERBE in racing consistently, but I'm starting to think most are using 5s or 6s and lower kV ratings.

There is a lot more to gearing for racing than just gear for 40MPH!!! When I started racing this spring I found that out in a hurry! I started out geared for 39MPH but when I chewed up my pinion I had to gear down a bit because it's all I had available. I wound up running faster laps with it geared between 34-35MPH. I couldn't blow away the nitros on the straight anymore but the power was much more useable and was still faster than any nitro on the straight. Your gearing will depend alot on your track. Also remeber that lower gearing will pull less amps under acceleration and give you a little extra juice for the longer mains. Gearing up and turning your end point down will lower your speed but pull higher amps on acceleration.

I see 40mph as the safe upper limit for racing; what I should be typing is " gear for 30-40mph depending on how tight and technical your track is. An open or larger track can use the higher gearing/speed more to blow past the other trucks on the straights, where as a smaller or tighter track can use the lower gearing/ speed to make the most of the added acceleration out of bends and along the shorter straights". Ofcourse, thats the long winded version of "gear it for ~40mph"... :lol:

E-Revonut, I know there's more to it than that. I just wanted to get an idea of where I needed to be pinion wise since I plan to order 3-4 pinions to get the truck going and give myself some options. I just didn't want to order, say a 16-17-18-19 setup and then realize I need a 20-21-22-23 set of pinions to be in the ballpark, those suckers aren't cheap.

Is anyone running 6s in there ERBE and if so what gearing are you running and what temps are you getting???

Click here for answers to questions like that....

:sarcastic::lol:

Not cool dude, Not cool:diablo:


:lol::lol:

:whistle:

There are a few people running the MMM system on 6 in the erevo for sure, cant remember their setups but check in the BL and revo sub-forums- more of a speed run setup bearing in mind the kv vs voltage..

i started a craze at our club...everyone who is on their first car equipted with a MMM runs 6s:surprised::lol:
everything from E-revo's, rEvo converts, RC8T truggies and various buggies!!

we are ALL geared for 40mph and no one has temp issues, the ones that drive hard may have the fan flick on for a really short while.
eagle tree data under 6s load and 40mph gearing only shows amp spikes of 70A:yipi:

my temps never go above 120 on the motor during racing.
my setup is:
rEvo 2.5 convert
E-maxx 3905 tranny, geared for 40mph with LST center diff.
turnigy 6s 30C 5000mah lipo
MMM 2200 combo
17t pinion, 65t spur (never ever stripped a spur since it was converted!!)
ESC fan only comes on when doing speed runs on grass (at 40mph)

something else i'd like to add...
when i gear for 40mph...i set the lipo cell voltages to 4.2v per cell...but as i understand...most people set them to 3.7v nominal voltage.
6s kicks nuts, i can crack 30 min mains, mate with similar setup might push 40 mins, cool temps, loads of power avaliable when you need it (screw up a jump, mash throttle to level out)

recomend it to any racer to run 6s...but i havent taken any consideration to weight though:lol:

speed run setup....pah :lol:

Thanks shaun that gives me something to compare to. I will run my eagletree as soon as i get home from work on Friday

Shaun, you've got me serious considering 6s, cooler temps sounds great, and while the batts are heavier, as low as they are in my ERevo, it could only serve to lower my CG.

needless to say because you are running the MMM at 100% and most likely running zippy quality batts...you will need to watch your setup.

like i said...i CANT get 6s power to the ground and the maximum i can pull from my revo geared 17/65 is 70A which is well within both the battery and MMM specs.

cool temps and loads of power are great!!
i did some reading a while back and i hear there is a TVS in the MMM that regulates breaking voltage. this being said, with low quality batts i run (the turnigy cells) i set my breaks to not be able to lock up. locking up the wheels on breaking is bad all round, you put huge load on the ESC and batteries and you cant turn the car with the wheels locked anyway!

having that extra bit of throttle left to pull a rolling wheelie on your last lap as you cross the line is priceless too:rofl::yipi:

Shaun, was that comment directed at me? I'm assuming not since I am running a Tekin T8 and will be getting TP batts, but thought I'd check. It just makes gearing way easier and should help keep my mind at ease... My only concern would be if it's legal to run 6s at my track... they're ROAR compliant. No biggy on the club stuff, but for big sanctioned races, the 6s would be a no go.

yeah..and there arnt that many good ROAR approved lipo's either that i know of..they should at least approve NEU packs!!
not bloomin maxamps:sarcastic:

dont think 6s is road compliant either:whip: it should be!!

out club was made around nitro and the electric class was started by me and somehow wormed it's way to have it's own class. but rules are just simple for us and we govern our own rules, gearing must be set to 40mph (to eliminate clear blitzing of each other) and only truggy and trucks are encouraged to race because buggy vs truck is not fair at all whereas well set up truck vs truggy = some kind of chance.

that's how we roll:yipi:

Hahaha, nice. Yeah, ROAR compliance is tough (to be fair, they're only evaluating packs that are sent to them). I know the 3s TP is ROAR approved, so I may have a work around purely on the fact that I'm running 2 ROAR approved Lipos at one time (I'll have to bug a ROAR rep on that one). I think the only restriction may be that I can't charge them both from a single charger at the same time. I dunno, I'll have to look into it. Either way, I like the idea of keeping my stuff cool. Temps play way too big of a roll on these big 1/8 brushless systems.

with a little thinking you can charge the 2 packs at the same time...
the charger will see them as a 6s pack.

you will need to make an adapter for the balance lead, so cells 1, 2 and 3 are immediately followed by the other pack's 1, 2 and 3 cells, then rig up a common ground, connect the packs in series with deans adapters etc and you have a saddle pack.

here's the catch those 2 packs MUST ALWAYS be used together no matter what! you wont be able to put one in your rustler and run that, they are always connected as a 6s pack.

Oh, I know that, I was hoping the 4s thing was more of a charging rule from ROAR than anything (not wanting you to charge too many cells at one time). I would prefer to charge them as a 6s, because that means the set is balanced for my E-Revo. Things to consider. I'm thinking I may end up 6s though, if for no other reason that cooler temps.

Ok Guys i finally got a chance to run my EREVO on 6s. My setup was CC 2200Kv setup, Hyperion G3 3s 5500 bats and geared 18/62. I was running on grass and dirt and it ran fine for about 15mins. I was checking temps regularly and at this point it was motor 140f-160f and speedy about 140f. Than my truck just stopped. I went over pulled the shell off and checked temps again, all good plugged it back in turned it on and it went about 3 meters and puff one MMM turned to ash:cry: again:diablo::diablo:
Luckily i had my data logger on at the time and recorded the whole run. The only high point was for 142A but at 3mins in. Nothing out of the ordinary after that.
What the hell is going on. I think i must passion fingers.

Bad juju?

Clearly the BL Gods are displeased with you for some reason- if there arent any obvious issues like binding, bad servo, bad motor or bad solder joint etc etc, there really is no explanation- just bad luck :neutral:

I had a closer look at the carnage today and realized that it was all around the positive terminal into the speedy. I guess maybe there was a bad solder from the factory or it may have broken during bashing?? The really bad part of all this is that i thought i would ease my sorrows and take out my VXL. that lasted about 3 mins untill one of the motor phases burnt out. The motor is a 36mm 5700, i am not very happy with Castle at the moment. Luckily i had a Hacker 6.5t motor not doing anything so i put that in but the torque isn't there