Why am I slow?
 

Sorry for the title...lol

I'm a bit disappointed right now and looking for some guidance. I've been working on a top speed setup for my 1/16 Mini E-Revo for the past few weeks. I made the initial speed runs today and am less than impressed and very confused. Please review my setup and let me know if anything is way off base or any theories you may have for my lack of speed.

1/16 E-Revo
Stock diffs and tranny
EZRun 60A esc
Neu 1112/2D motor (3250kv rated)
ESC timing 15 degrees (this is the EZRUN default, not sure if that is best)
Custom motor mount (see below)
ParkBEC 6v
Ko Propo ex-5 UR radio/receiver
HS-5085MG servo
45t spur gear
Various pinion gears (35, 39, 43, 47)
2 - Hyperion G3 VX packs (2S, 1800mah) in series
HPI Super Nitro belted slicks and rims (measured 9.5" circ., 3.0" diam.)

So, as you can see, I made my own motor mount and tranny plate. The stock setup would not allow for any more than a 35t pinion and the Neu 1112 contacted the rear shock mount. So, I made this setup in my garage. This si the first time I've tried somethign like this. I don't have a mill or anything cool like that, just a drill press and hand tools, so be nice :oops: Anyway, this setup can fit the largest pinion gear I can find (47t) with room to spare and the motor clears the shock mount.

I made a bunch of runs today and seemed to hit somewhat of a wall in the mid-60's (MPH). I ran everything from 35/45 gearing up to the big 47/45 gearing. Each run was between 62-66 MPH. Now, I never got a prolonged full throttle run, I usually came up to speed and was maybe just touching full throttle for a split second, if at all. Regardless, I expected to be running much faster. Additionally, I can't figure why my gearing changes had no noticeable effect on speed. I must have made 30 runs easily and they were all about the same. Normally, I would think this means the motor is just unable to push the truck any faster, but others have gone much faster on "lesser" motors. I expected this Neu would have enough power that it would be the last of my issues. Temps never got super hot. The motor was usually around 120-140, hitting 155 once after a long string of runs. The ESC never got above about 130 or so. I recalibrated the ESC once to make sure it was seeing full throttle from the radio. I also have a ziptie pulling the rockers together so that the suspension rests just above bottom.

BTW, for those that have not been following the mini revo. There are already a few folks that have recorded 81-82 MPH runs. One even managed it with a stock esc/motor on 4S, although he knows he is on borrowed time. I've spent lots of time on BrianG's tope speed calculator and see no reason why I am not going faster.

I have plans to hit a longer road tomorrow to see if I can get full throttle for a few seconds straight, but I'm not expected much of a change. This has been fairly disappointing for the money and time invested. I feel like I'm using the right parts, but maybe I missed something. Maybe my driving is an issue, just not sure. So tell me guys, what do you think?

Pics of my setup...Thanks!

http://www.nuibe.com/rc/minierevo/sp...vo_speed_1.jpg

http://www.nuibe.com/rc/minierevo/sp...vo_speed_2.jpg

http://www.nuibe.com/rc/minierevo/sp...vo_speed_3.jpg

http://www.nuibe.com/rc/minierevo/sp...vo_speed_4.jpg

http://www.nuibe.com/rc/minierevo/sp...vo_speed_5.jpg

http://www.nuibe.com/rc/minierevo/sp...vo_speed_7.jpg

http://www.nuibe.com/rc/minierevo/sp...speed_mm_1.jpg

http://www.nuibe.com/rc/minierevo/sp...speed_mm_2.jpg

http://www.nuibe.com/rc/minierevo/sp...speed_mm_3.jpg

poor schooling? inbred parents?:neutral:

Did you run your setup through BrianG's speed calc to get an estimate of what to expect speed-wise? Sorry I can't be more helpful, awesome Mini Revo though.

:rofl:

Sorry. Nice ride you got there.

Yeah, and it should be a bunch faster.

My parents are only 2nd cousins, so I should be all good...

you said you only touched full throttle for like a second. did you run out of room? I'm thinking since your pushing the limits of what the r/c is physically capable of your spool up and top speed are probably similar and you just need a place where you can really open her up and let her fly.

BTW: it's awesome you joked with me and didn't get your tighty whities in a bunch over my first comment. A+ motor mount and ride. I like you already!:tongue:

Have you tried better tyres? Tyres with more grip? How about using a lid with more aerodynamics? Maybe the Mamba max will push it further?

Either way that is a great lookin setup.

I would adjust the timing back to zero and see what you get. I have a feeling it could be causing and issue. The tires would be my next choice. Maybe see about some foams.

Check your suspension settings. It's difficult to tell from the pictures, but it looks as though you are running front toe-out which is going to scrub a bunch of speed off straight away.

Sweet looking truck though, 66mph is still hella fast!

_paralyzed_, you'll have to do much worse than that to get me upset :na:

I'm going to try a longer road today. The previous runs were on my street in front of my house, which is a long straight road, but it's got cars parked on the side and just not that wide.

I'll also try 0 timing today. Like I said, the ESC came defaulted to 15 degrees and I read on the Neu site that my motor should be 0-10 degrees. So, I will run 0 degrees this morning, on a much longer wider road. As for tires, I thought I was doing the right thing by getting belted slicks. They definitely don't seem to balloon. As for pushing the limits of what the car is capable of, based on other peoples efforts that is not true. I'm not even close to where I should be. I seriously expected 20MPH more than I'm getting.

I'm seriously wondering about the ESC now. IF I am able to hold it wide open today and it doesn't go a bunch faster, then I wonder if I'm hitting some current limit on the ESC or something.

it might be a RPM limit like on the traxxas escs...

ever think about wind drag??... and terminal vlocity:whistle:

Not when others are doing 80 mph. Let's not forget, these little trucks will do an honest 50 mph stock, with 2 nimh packs.

Do you have your slipper tight?

I have a feeling you need a longer road, just because you are hitting full throttle does not mean the truck is at full speed. When I did speed testing with a 10th scale touring car, I picked up 10mph just by moving the radar gun about 200ft down and giving the car an extra 50ft before I started braking. I think you will see the difference with a longer road. How are you determining speed? Bushnell radar gun was what I used.

The only reason I mentioned tires is the possibility those slicks are losing grip, although I really don't think that's it.

will 2x 2s 1800 mah fully power it ? test runs showed you gained 10mph using an 8000 mah over a 5000 mah in a rustler by some manufactuers in speed tests. I run more in my transmitter (2400 mah 2s) my micro T that weighs 3oz runs on a 1800 mah. Just my thoughts, im usually way off

The slipper is very tight and shows no signs of excessive wear. I ran agin just now in a commercial area with much more space. Same speeds as yesterday. I am still not getting extended period of WOT. I roll inot it and get up to 80-85% throttle (just a guess) and as soon as I get to WOT the front lifts. Several times I passed my friend holding the radar doing 65 mph with the front wheels off the ground. I'm not sure if this is a power wheelie or an issue with aerodynamic lift. When the batteries started going off a bit, I was finally able to go WOT for the last bit of the run. In those runs, even witht he batteries going a bit soft, I still ran 65 mph.

Not really sure what my next step is, or how the heck these others guys have run 15mph faster than this.

I can't fit a 4s battery in here. I bought the best batteries I knew of in the G3's. They are rated at 35C/65C, that's 63A continuous and 117A burst.

Have you made any mods on body??
I think you realy need to focus on airdynamics to get it go faster and get downforce to keep front end down.

yeah I hear ya that seems more than enough then. I think that extra mah more applied to when lipos were 15c piles. Just threw it out there. 65 is pretty fast on 4s I agree with the homies, build a super aerodynamic nosecone lol

The body is still stock. I think I am going to try sticking a wing on the front next, or some type of splitter. I figure that will increase downforce and eliminate some of the flow under the truck. Just need to find an appropriate wing I can use now...

Obviously your speed threshold has nothing to do with the motor or batteries. Aerodynamics is the ONLY thing that should matter. Next time you are on a highway, stick your hand outside the window and see how much force the wind can push. That's likely the same amount that is pushing against your mini revo. For starters you need the chassis to be as close to the ground as possible by maybe putting some foam underneath to fill in the space if you can't get it low enough. You also need a body that completely covers the wheels.

I haven't read the whole thread, but are you running with body on, or off? Off would take alot of top speed away because of the components are obviously created alot of drag.

If you want to make a record, make a tail cone, will make a bigger difference than a front cone, trust me. :smile:

Stock body is on. It is starting to sound like I need to make a front wing/splitter to reduce front lift. Also sounds like foam tires wouldn't be a bad idea.

I would also try a little weight in the front before a wing in the front.

I think you need disc rims also. At least thats what they use in all 1:1 speedrun cars.

Now that the center diff is available for this truck, I'm going to give that a shot too.

I'm running my buggy (frankenstein's ride hyper 7) with some lead on the front bumper to avoid wheelies. the problem is that its a normal, short buggy chassis, and with the truggy wheels I get wheelies on full throttle, as soon as the torsen center diff is locking. some weight in the front helped a lot, because the faster you go, the more wind lifts your buggy. still, I get wheelies sometimes (like 50 meters, off-road!!).

next step would be a proper and aerodynamic shell, and probably a front & back wing for more downforce.

regarding the timing, I don't know if 0 deg. is the way to go. usually, higher timing causes higher rpm's and power output. but the torque is decreasing the higher the timing is, and 15deg. might be too much, and the motor is missing some torque for that extra speed. even that it's just guessing, have a try with 10 degrees.

another idea, maybe you make a new throttle-setup with the esc, just to be on the safe side.

and hey, awesome revo!

A center diff would be a waste of time for speed runs, you want all 4 tires going the same speed at all times, trust me.

+1, a solid center will make you wheelie worse but you'll get the power to the ground rather than waste it away unloading the front wheels.

Damn, ok. So I'll go forward with the front wing and see where that gets me. I'll have some extra weight on hand to add if necessary too. Once I can get this thing to go WOT for several seconds straight, then I can go back to compaining about not having enough power :mdr:

Updates
 

I tried out the front wing this afternoon and it was a failure. I was getting downforce, but it made the truck handle weird and it was just too easy to bend it up. I think it was too big of a wing for such a short wheelbase truck. I scrapped that and went with the adding weight idea. I strapped a 1/2" x 2-1/2" socket extension (approx 140 grams) to the front of the chassis and put in 43/45 gearing. This kept the front end down and allowed some better runs. I was able to get up to 73 MPH with this setup before I damaged a tire. One of my HPI Super Nitro belted slicks (part #4598) broke a belt, as best I can tell. Check out the picture and you will see two flat spots while the rest of the tire is good. The tire feels firm due to the belt everywhere except between the two flat spots. Needless to say, that one tire has a pretty bad baloon and wobble now. The additional weight definitely affected the acceleration, but at least I was getting into full throttle. I could tell it is still accelerating slowly after hitting WOT though, so I know there is more in it.

One interesting note...I have been using BrianG's speed calc a lot to try to understand what is happening. I have confirmed that this motor does not seem to want to turn more than about 48k RPM, even with low gearing. This tells me that my 4S setup is making no more than 14.8 volts. Even though the lipos have a nominal voltage of 3.7V/cell, I figured they would be closer to 4.2V/cell when freshly charged. They measure that high right off the charger, but then they must be dipping to 3.7V or lower under load? Maybe this is the result of only having 1800mah of capacity? IF I am going to be limited on voltage, I should have gotten the next higher KV motor. Or, I could just get a single 3S pack to run a 5S setup :)

http://www.nuibe.com/rc/minierevo/tires/broken_belt.jpg

it definately sounds like your batteries aren't up to snuff when it comes to the motor needing more power under such high gearing.

Aren't these Hyperion G3 VX packs about as good as I'm going to get?

the 80+mph 1/16 revo's i've seen were running 2 SMC 2200mah 30c in series and 75+mph 3S Thunder power 4200mah 40c.

I don't know if you're splitting hairs over 400mah, but for larger scale models, higher mah will have a definate effect on acceleration and how fast you can get to top speed.

the neu's can be amp hogs and if the battery is too low in milliamps, it's definately going to effect acceleration. so there in lies another problem.

in theory, a lower mah battery should be able to get to the same top speed as a slightly higher mah battery, but it will take a longer distance to do so. if you don't have the space to get to top speed, hold it, and let the motor completely wind out, it dosen't suprise me that low 70's is all you're getting. i think the solution is either a longer road or slightly higher mah packs.

Would it be worth going to a higher mah pack, if I have to go to a lower "C" rating? For instance, I have a pair of Flightmax 2200mah 20C packs.

imo, yes. since there is no real standard of testing a true C rating, they're all subjective, company to company.

besides, the C rating dosen't really even become a significant factor until you get into heavier cars and trucks but milliamps have proven to be very significant in smaller scales.

eagle tree data has shown 12C packs that were rated 8000mah were up to 10mph faster than 20C 5000mah packs in a vxl rustler.

OK, then next test will be a longer run with the Hyperions and then I will also try the Flightmax 2200's and see what they can do. Thanks for the idea.

One other thing I am wondering...could the EZRUN 60A ESC be holding me back. I wonder if it would go faster with an MM in there...