burythesystem

Alright guys, I need some help. I just installed a BZ Tuned Motor into my Sand Viper, and the thing is wild and erratic, just all over the place. When running it in gravelly dirt, it automatically goes into doughnuts, without steering. So I take it over to the park, and I run it on some grass, where the grip is a bit better, but when turning the car, it just spins out and goes all over the place. Additionally, when it hits sand, the tires just spin like mad, and the cars goes almost nowhere. One more thing........... on a fully charged Tenergy 5000 mAh NiMH battery, total play time was 12-15 minutes. Something seems very off.

I researched to the extent possible, and found virtually no useful information pertaining to why this might be happening. I can accept that my tires (stock Sand Viper) are probably not fully up to the task, and I need something better, but I just did not expect my Sand Viper to be so cracked out.

If anyone can point me in the right direction towards recovery, it would be much appreciated.

EXT2Rob

My Feedback: (1)

Ha ha ha....the title and description cracked me up! (oh, I made a little pun there myself, ha!)

Sounds to me like you're just completely over-powered. Your buggy looks a lot like your basic 2wd rear-motor RC. Probably weighs about 3.5lbs.
I don't know what a BZ Tuned Motor is, but from your description, it sounds big and powerful. Too much so. I have an Evader, which started as a brushed-motor newby-mobile which I eventually converted to brushless. I used this motor system which only uses a small-ish 380-size motor and a 35A ESC. But that little system with the 4300kv motor will push it to 40mph. I even used the same motor system in a small 4x4 truggy (Ofna Hyper 10TT) and it works great. Those little brushless motors are powerful!

But you put a big honkin' motor in a light weight 2wd buggy and punch it on dry ground, and it's gonna be donut-shop city. Putting big power through two wheels in a light RC requires throttle control and a smooth throttle finger.

That said, you could also be experiencing "diffing-out", where one drive wheel looses grip, then all the power goes thru that wheel, spinning you out. You could try tightening up your diff, either by adding thick diff fluid, or grease, to the diff if it's a gear diff. If it's a ball diff, tighten the diff adjustment screw. Keeping BOTH rear wheels turning at the same time is the goal.

burythesystem

Thanks for the feedback, I have some ideas.........

Here is the pertinent data on the motor:

http://www.amazon.com/Tamiya-53930-S.../dp/B0038PBNPK

Winding: 23 turns
Proper voltage: 7.2V
Rotational speed no load: 26,500 r.p.m (7.2V)
Torque at maximum efficiency: 49mN · m (7.2V)

Its quite a bit more powerful than the stock silver can.

With that in mind, should a 5000 mAh NiMH battery only last 12-15 minutes?

EXT2Rob

My Feedback: (1)

Yep, that sounds about right for run time. Shy of five minutes perhaps. But if it is a system that draws a lot of power, that could account for the five minutes if you were heavy on the throttle. Nimhs aren't as good as Lipos for high power applications. And for heaven's sake, ditch those Tamiya Molex power plugs. Use Traxxas or bullets.

burythesystem

Forgive my noobiness....... this is a brand new hobby I will have to pick up some Lipos and ANOTHER frickin' charger. Man, the learning curve is getting expensive.

phmaximus

He he, if u think that's powerfull, chuck a brushless combo in there...then she will be mental

for the traction issues. I'd take a closer look at these.... Tyres, diff and gearing

burythesystem

Yeah man, I have no doubt that a brushless would be straight jacket territory. So I have some super knobby offroad tires on the way, and luckily, when I picked up the motor, I included some 500k diff oil. I will be cracking open the diff within the next day or two and supplying a ready amount of the stiff diff stuff. As far as gears are concerned....... the only options that I am aware of that is changeable on this buggy is the pinion. Luckily, I also have two steel pinions on the way, 17T, and 19T. According to a thread on another forum, the pinion to use with the BZ motor is the 17T. I will correct each of these areas, and report back on the results as I go.

Cheers man, thanks for the info!!

Lunchboxer

Post some video.. !

burythesystem

I will try to take some videos this weekend, showing it in it's current, methed out state. First plan is to break down the diff, clean, and add new diff oil. Still waiting on tires and pinion gear. Probably going to be a few weeks on those, ordered from Hong Kong, will be arriving on the slow boat from China. I also have a ball diff that should be showing up any day. There is a lot of positive feedback on the ball diff from what I can see on the forums.

burythesystem

Another question related to my tires...... should I be concerned about foam inserts, or is that a waste of time?

collector1231

My Feedback: (1)

It doesn't really matter until you get into racing.

burythesystem

So I now have a diff full of 500k diff oil. Wow. That stuff is THICK!! No videos were taken prior to changing the diff oil, just did not have the time, and did not want to wait. The car is no longer diffing out, but is still all over the place, mainly from lack of anything resembling grip, the tires are about 90% bald. Some good news though, my package from Hong Kong arrived super fast!!

EXT2Rob

My Feedback: (1)

The open cell foams that come with the tires are fine, mostly. I sometimes found that they would go off before the tires were worn out. But I learned that you can slice into the inside tire bead with a hobby knife, remove the old foam and pop in new ones. The bead can be re-glued, and off you go.

burythesystem

After swapping in the 17T steel pinion, I am pleased to report that the nose stays planted, the motor temps are cooler, and I got about 25 minutes of spirited playtime out of my battery!! I am off to the RC shop this after noon to buy some tires. Just found this place yesterday online:

http://www.rc-siro.com/

DieHarder

I know what you mean. I get so sick of my half worn tires being spongy from the foams that have degraded. My front tires on the Evader last forever, but the backs are just awful. I'm afraid about the part of regluing the bead. Those tires take so much abuse since the thing is so overpowered, I just have my doubts that the bead would hold or still be balanced on those 3S speed runs. I'm considering 'strapping' my next set tires with duct tape like they do on 1/8s.

burythesystem

Alright, so I have the ball diff installed, and new tires. Everything works great, this thing is super fast, but the only tires they had available are not really made for grass or rocky dirt. So I still need a full set of knobby tires more suited to the terrain, but other than that, I am really pleased with how everything works. Only issues right now is heat, the motor cut off on our last outing. So I am going to cut the rear casing to expose the motor to more air, and I have an aluminum heatsink I will be attaching. As temps are only going to go up here in Okinawa, I suspect this will become more of an issue as the hotter months are soon upon us.

I also picked up the blue suspension seals, as the suspension leaks quite a bit. The guy at the RC store said the stock red seals are junk, so he recommended the blue seals, and a pack of medium weight fluid, as the suspension is pretty soggy. I will probably tackle that this weekend.

EXT2Rob

My Feedback: (1)

Nate, I sliced and re-glued several sets of tires, on the rear. NEVER had a problem with them coming unglued again. The cut edges mate together perfectly, and because you're gluing rubber to rubber with the CA glue, it doesn't let go. Trust me, it works.

Bury - if your system shut down because of overheating, then you should drop your pinion a tooth or two. Gear down. That is how you control motor temps.

burythesystem

Rob - The only pinion options available on the DT-02 are 17T and 19T. Other than modding the mounting points for the motor, and I am not savvy enough to pull that off.

EXT2Rob

My Feedback: (1)

Ah yes, I re-read your earlier post that you did put in the 17T pinion. And you fixed your diff issues. Good.
If the car shut down due to overheating, it's the ESC that shut down to protect itself. (You can run a motor until it melts something, and the ESC won't know nor care)
I'll bet that Tamiya ESC doesn't have a fan on it. Find a 25 or 30mm 5V fan, and mount it to the speed control's heat sink. That should do ya.

burythesystem

Rob - You are correct, the Tamiya ESC does not have a fan, so I will have to address that issue soon. Okinawa is now moving into perma-summer, as it does every year about this time, so I need to do this ASAP.

In other news, yesterday I cut a big chunk out of the gearbox, inspired by this:



That also allowed me attach a fat heat sink that otherwise would never have fit with all that plastic in the way. Feeling good about motor temps, but now I need to turn my attention to the ESC.

The other thing that happened, I broke my servo saver. So things are down until I pick up another one. I tried to super glue it, but apparently the type of plastic the servo saver is made of has super glue repellent properties, it did not hold at all. So I will be ordering up an aluminum servo saver shortly. As always, one step forward, two steps back.

collector1231

My Feedback: (1)

For the ESC, buying an XL5 ESC or other brushed ESC would be a good upgrade. Mounting a fan on it is kind of a pain in the rear.

burythesystem

Collector - Thanks for the suggestions, that seems like a good way to go.

burythesystem

Got my suspension rebuilt with upgraded silicone seals and heavier 700 weight fluid. Much firmer feel, can't wait to get it back out and give it a good bash. Still need to get a server saver. I even tried to glue the servo saver back together with Gorilla Glue. After letting it cure overnight, it came apart when I was installing it like I had used Elmers school glue.

Will be upgrading my ESC sometime in the near future. Once that's done, I am hoping there won't be a need to upgrade or fix anything for awhile.

dfjdv

Yep, that sounds about right for run time. Shy of five minutes perhaps. But if it is a system that draws a lot of power, that could account for the five minutes if you were heavy on the throttle. Nimhs aren't as good as Lipos for high power applications. And for heaven's sake, ditch those Tamiya Molex power plugs. Use Traxxas or bullets.

burythesystem

I will also be getting rid of the Molex plugs, on the suggestion of basically everyone.