RPM VXL Rustler, 70 mph setup

[Nitroelectric]

Where did you buy those mamba stickers. I would love to have them on my rusty!

[ttThree]

They come with the mmp esc when you buy it. Look on ebay maybe some one sells those. Or even better, make castle send you some for free. I have had shops sending me stickers for free.

[Nitroelectric]

Kk thanks. I really dig the look of them and love your rusty build. I'll be getting some parts in the mail soon for mine. Like more wheels and a wheelie bar. Yours looks so neat and clean. I gotta work on that for mine lol

[ttThree]

Thanks, it could be more clean and neat but that involves individual cable sleeving with heat shrink, and I dont have time for that. Good luck with your build as well. My rusty is the little brother compared to yours because you run the "big block" motor .

[Nitroelectric]

Lol thanks and lots of luck to you too. I'm excited for both of our "finished products."

[ttThree]

My truck is more or less finished, but I dont have a proper gps yet. I will soon recieve a gift card to a electronic shop, and then I maybe buy a gps. Unfortiunatly the weather has been up and down so I cant run anyways, plus I have other stuff do these days.

Before I do anything else I must organize all my tools because its quite a mess now...

[Nitroelectric]

Lol well I can't wait to see a vid if you make one!!

[ttThree]

These days I have been shimming. There were some play in the front and rear arms, causing the rustly to pull to the side while accelerating hard. I put one teflon washer on each arm and now it is no play, making the rustler to track more straight while accelerating. One problem is also the rear screws holding the arms keeps backing out, making the car unstable after a couple of runs. Im seriously considering getting the STRC hinge pins with lock nuts, or any other hinge pin kit.

I also reduced the sensitivity of the gyro, because the rustly became wobbly in the front while the gyro corrected every movement. This isnt good at high speeds. One reason the gyro seems more faster now than before could be that I run external bec nowdays, which gives the servo and gyro more constant power and hence increased speed in the servo. It could also be due to my alloy bellcrank, which gives a more responsive steering.

Anyways I filmed my run today, nothing major. Unknown speed due to no gps.
http://www.flickr.com/photos/50755904@N08/7538811128/

[Cipher_Jones]

I've been a big Castle fan for years so I cant fault you for wanting to go Castle but I wish you would see your goal to break the 70 mph barrier with the VXL through to it's end. It can be done and you have what you need for the most part just a matter of finding the right gearing and the smooth run with no hiccups and you are there. Then you could always go with the Castle set up and set a new goal.

I dont like GPS's for speed runs, radar is way better and more accurate.

I am still a Traxxas fanboi, and I know we aren't supposed to say anything negative on the forums, but at this point I am pretty much going to have to say 'false advertising' on the speed's posted on the boxes. I have radar and GPS telling me my RC is not as fast as advertised multiple times over, and many youtube video's backing that up.

[ttThree]

I think you can achieve over 70 mph with stock system and anacondas on 31/76 gearing, even 71 mph according to gps. According to speedgun I dont know.

[Cipher_Jones]

I think you can achieve over 70 mph with stock system and anacondas on 31/76 gearing, even 71 mph according to gps. According to speedgun I dont know.

Well, I still think Traxxas is great, the fastest thing you can get "out of the box", and would love to see a gps or radar verified speed run of 70mph stock. If you know of one please link.

Either way the speed I have achieved were 'close enough for government work' I guess.

[ttThree]

Look on youtube there are some gps runs I think. How ever speed isnt my main issue now, its tuning in the car, and see what other parts I need.

[ttThree]

Update of today:

Some videos of last days run, no gps or camera stand.





More to come, bye

[Nitroelectric]

All I can say is wow that's fast! Great setup

[ttThree]

Thank you, I have got to a point where the car runs fairly stable, due to centering the servo and adding some toe in. I just hope I dont crash again so I have to do it all over.

My next step will be to make some kind of mount for the on/off switch. Also im looking for a T-Bone rear skid plate, and STRC hinge pins. I use a home made skid out of alloy, but it doesnt protect the whole engine, it also weight a ton. And yeah, a gps of course, im just doing runs for fun now.

Another video is up tomorrow, boy I had to sweep the whole road because there were alot of small rocks and gravel on the side, making it extreamly unsafe to run. But 20 mins of hard labour was worth. The foams are really sensitive if there are rocks on the road.

[Petertje60]

I drilled a small hole in the rear end of the chassis and mounted the switch there. Looks like it's not too easy to reach for, but it's not that bad.

[Desert JATO]

it looks speedy. if things went fine with you , you'll reach a higher top ends .. i wish

[ttThree]

I have thought about the idea to mount the switch in a similar place, Ill see what I come up to.

[Nitroelectric]

I double sided taped mine to the side of the chassis and that works great. Plus I didn't have to fabricate or drill anything

[ttThree]

Okay after doing some runs I feel that my rusty is pulling to the left side while accelerating. This happened before I installed my mmp and 4600kv motor, and before I crashed. How ever it was pulling much less, hardly noticable. When im braking it tracks pretty straight.

This picture illustrate the scenario:


This happens when im accelerating in the beggning of a run. When im up to speed the car tracks straight again. The red circle illustrated heavy acceleration and maybe some wheelspinn. Thanks to the gyro I can get the car on track again.

There were some play in the rear arms, but I have reduced that my putting washers. Also this problem gets worse when the rear arm pins are backing out. But still even if I tight them to the point that there is no play in the rear arms, the rusty still pulls to the left while accelerating hard.

I have done this to eliminate the issue:
- Shimming front and rear arms
- Centered the steering
- Adjust steering trim
- Add some toe-in to the front
- Check bearings
- Check tranny and differential
- Balanced the wheels
- Check for play or binding on other areas
- Shocks, they are all equally soft/hard
- Checked pins holding the arms, castors, bearing carrier, etc.

What may be the cause:
- Wobbly front wheels, the Jacos are really wobbly, ill upload a video later on. How ever they were like that from the beginning and the rusty didnt pull to the left that much.
- One bearing on the left side in the tranny was binding. How ever this would make the rustly to pull even more when letting off the gas.
- More powerfull motor. The 4600kv motor has more torque, making the wheels to spin more while accelerating.
- Differantial - To much power for the differential to handle, making the wheels to turn uneven.

Personly I think it must be the added power that makes the rusty to pull to the left, because with the veleneon it was pulling much less. Either the wheels are spinning causing the rusty to pull, or the diferential cant make the wheels to rotate equally. Also, when the battery gets low, I experience less pull due to less power comming to the wheels.

Is this a common problem, any tip to prevent it?

/tt3

[AbSoLooT1]

Right on TT. hey! I got some awesome material for ya. Its from Racers Edge, its called Kydex. Its plastic, comes in a like 9x12 inch (about sheet of paper) size, and 1/8 inch thick or so for ten bucks. perfect for ESC mounts, or ESC straps. (such as snappy RC)



if ur still looking. But looking good!

Check out my thread: New Rustler Build, Im about to update it in a sec with the new stuff.

[KeltiKrewser]

What may be the cause:
- Wobbly front wheels, the Jacos are really wobbly, ill upload a video later on. How ever they were like that from the beginning and the rusty didnt pull to the left that much.
- One bearing on the left side in the tranny was binding. How ever this would make the rustly to pull even more when letting off the gas.
- More powerfull motor. The 4600kv motor has more torque, making the wheels to spin more while accelerating.
- Differantial - To much power for the differential to handle, making the wheels to turn uneven.

Personly I think it must be the added power that makes the rusty to pull to the left, because with the veleneon it was pulling much less. Either the wheels are spinning causing the rusty to pull, or the diferential cant make the wheels to rotate equally. Also, when the battery gets low, I experience less pull due to less power comming to the wheels.

Is this a common problem, any tip to prevent it?

/tt3

I decided I'm going to turn my old Stampede into a speed runner and I've been scrolling thru your build all day at work. Very nice Work!

Sorry if this has been addressed, but have you balanced the wheels? Made a huge difference on my MT, I would expect it to make an even bigger difference at the speeds you're running.

I also agree with your theory on the diff. What weight fluid are you running in it? I would expect a thicker weight fluid might help with "torque steer" and may also explain why it's gotten worse over time, as the fluid may have broken down some.

[Petertje60]

Since the Jacos are very flat, they need to have exactly the same camber settings left and right. I had a very tiny difference once which was enough for a serious problem just like yours. If you car pulls right during acceleration, change the settings of the right rear end and vice versa.

[Desert JATO]

Differential lube could be ? Since when did you last time you opened and grease you diff ?

[KeltiKrewser]

Differential lube could be ? Since when did you last time you opened and grease you diff ?

My Bad. Been about 10 years since I tore into my 'Pede, and I forgot how the trans/diffs are setup.

I've been running 1/8 scale and 1/16 stuff, both of which have fluid filled diffs, so I'm just used to tuning with diff fluid.

[ttThree]

Thanks your your tip, ill will look into the camber settings and make sure its equal. Ill will also put som thick grease in the differential. Diff flud will be a problem because diff isnt sealed. What more, yeah the Jacos are balanced, not 100%, but better than stock. Didnt feel any differance after balancing though, just less vibration in the rear end.

Ill tell you what I come up with.

[KeltiKrewser]

I appologize for my ignorance on this subject. Like I said, I'm just starting to research for my first "Speed" build.

This is what I was thinking of when I replied regarding the diff. I forgot the stock diff is not sealed. Might be an option if you continue to have problems.

I agree with Peter on the importance of suspension geometry, however, based on your diagram and explanation, it sounds more like a torque steer issue than a geometry issue. If it were a geometry issue I would think it would be happening throughout your run and not just at acceleration, although it might be magnified during acceleration. Then again, I could be wrong, it's happened before.

HERE is another option for a sealed diff.

[cunawarit]

If the diff is struggling to apply power equally to both wheels. Why not lock it and effectively turn it into a spool?

If it is mostly a speed run machine that's going to run in straight lines, why not?

[ttThree]

Yeah, it is just annoying because when I run I usually line up the rustly to the right side of the road to compensate for the pulling to the left while accelerating, but when im driving back I some times forget to place the car on the opposite side, making it a potential risk to drive out of the road. My diff is packed now with some kind of thick grease, I will se how this works. In worst case I seal the diff according to youtube videos, and put 300000-500000 fluid in it.

I tired to warm the grease with a lighter a couple of seconds and it didnt transform to liquid, which makes me think it holds high temperature. As mentioned before I use the stuff I have laying around.

/tt3

[ttThree]

Okay lets see here,

Front camber, it seems pretty equal for left and right?


Rear camber, also pretty equal.


I have done this to eliminate the issue:
- Check camber front and rear
- Thick grease in diff
- Replaced binding bearing

How ever, the left rear wheel seems to be more worn on the inside, while the right wheel is worn all over. This indicates that camber may have been to much on the left side. This combined with the torque steer could be the issue why it pulls to the left. If one wheel isnt worn on the whole surface, then the car may pull to one side while accelerating.

Left side on the rusty seem to be problematic, because of:
- Rear wheel worn on inside
- Previously wrong camber setting
- Previously too soft rear shock
- Bearing on left side was binding

Lets see if I still get any pull tonight, if not then its all good. If problem still occurs, well who knows what to do. I could possibly test with the stock wheels in the rear, because they are not worn at all. How ever, the balloning may cause problem.

Anyways, some pictures from yesterday





/tt3

[Dadx2mj]

Do yourself a favor and get a RPM camber gauge. Your square is a good idea but in the end it still relies on your eyeball and small differences might be missed.

Torque steer is not a factor in a Rustler because the motor spins front to back not side to side so any effect the torque has will not make the car move side to side but effect weight transfer front to back.

Another possibility is shock oil level. If one rear shock has less oil it will compress faster and that can throw your tracking off on hard acceleration.

[ttThree]

Okay, I must have missunderstod the torque steer, but I mean the diff then, not beeing able to rotate the wheels equally under heavy acceleration. Oil level possibly before, some weeks ago i refilled all my shocks and they feel equally hard. How ever this are estimations, as with the camber. Not 100% the same on all wheels, but as good as you can get with a ruler.

But to be sure I can, as I mentoned before test with stock unworn wheels, and then put spacers in one of the rear shocks, to see if I get any pull. If the pull becomes worse, then its a indication that one of the rear shocks is harder/softer than the other.

[KeltiKrewser]

Torque steer is not a factor in a Rustler because the motor spins front to back not side to side so any effect the torque has will not make the car move side to side but effect weight transfer front to back.

Another possibility is shock oil level. If one rear shock has less oil it will compress faster and that can throw your tracking off on hard acceleration.

Pretty much every front wheel drive 1:1 car on the planet has the same type of layout, with the rotation of the engine/motor parallel to the movement of the vehicle. Ask anybody with supped up Civic if your theory works out. If the diff applies different amounts of torque to each side it will pull to one side or the other.

As for the shock oil I totally agree.

[Dadx2mj]

Ask anybody with supped up Civic if your theory works out. Unless you have a LSD it will torque steer. If the diff allows the axles to spin at different speeds it will pull to one side or the other.

A diff allowing one wheel to turn faster than the other is not "torque steer". People may call it that but it is not what it is.Torque steer is when the rotation of the motor "torques" the motor to one side making it steer in that direction. When the motor rotates front to back it can not steer the truck side to side.

[KeltiKrewser]

A diff allowing one wheel to turn faster than the other is not "torque steer". People may call it that but it is not what it is.Torque steer is when the rotation of the motor "torques" the motor to one side making it steer in that direction. When the motor rotates front to back it can not steer the truck side to side.

You caught me just as I was correcting myself, but you're still wrong. If what you are saying were correct, then Longitudinal layouts (typical rwd cars, and pretty much every 4wd rc on the market) would torque steer worse than Transverse layout (typical fwd cars, and most 2wd rcs) which is not the case.

From Wiki:

Torque steer is directly related to differences in the forces in the contact patches of the left and right drive wheels.

I'm not sure what you call what you're talking about, but its not torque steer. If your motor is moving around enough to affect your suspension and steering, you've got bigger problems.

I'm not saying the rotation of the motor is "steering" the car, the torque being put to the wheels, thru the diff, is steering the car.

[Dadx2mj]

You caught me just as I was correcting myself, but you're still wrong. If what you are saying were correct, then Longitudinal layouts (typical rwd cars, and pretty much every 4wd rc on the market) would torque steer worse than Transverse layout (typical fwd cars, and most 2wd rcs) which is not the case.

We will just have to agree to disagree then. IMO the typical 4wd with the motor mounted length wise more prone to torque steer but the fact is there is just not enough rotating mass to cause torque steer. If it was torque steer in these car we would have have issues with it and guy who put the bigger 1/8thscale systems and run high voltage would have a nightmare trying to counter act it. They dont simply because there is not enough rotating mass to cause it and in a 2wd car it is rotating in the wrong direction.

[ttThree]

Okay, back from testing with some intresting results.

The thicker grease along with a new bearing in the tranny did help abit. Under heavy acceleration the rusty doesnt pull as much to left. But it is still noticable, specially after doing some runs. This is due to the grease looses its thickness slightly when its heated I believe. It could also be that some of the grease has leaked out, because the diff isnt sealed. On the first runs I could spin the tyres and accelerate all way in a fairly straight line.

I have come to a conslusion that when it pulls to the left, it is when the wheels are spinning, because you can hear it and even see it (tested with the stock ones, and it was still pulling under wheelspin). That explains the rusty tracking more straigh during acceleration when lipo power is becoming low. Easy, not that much power to the wheels.

I also tested to put spacers on one shock to see if it pull is due to one shock beeing harder than the other. When I had no spacer on the left shock, the rusty pull even more to the left. And when I had spacer on the left, and no spacer on the right, the rusty did track pretty straight. How ever this could be due to the decreased power in the lipo. I also tested to run without any spacers, and spacers on both sides, and the truck tracked straight again.

I dont know what to say, it seems to be a combination of problems, like the diff has problem to rotate both wheels equally under heavy acceleration, specially after a couple of runs when the grease is more loose. And it also seem to be an issue on the left rear. It could be the shock some how, but also the camber.

Even if the thicker grease did increase the straignt line ability under acceleration, I still believe its not only the diff that is/was the problem. What ever it is, it gets worse with more power to the wheels, which can explain why it didnt pull that hard to left with the stock vxl system.

Afterall, the truck tracks a little bit more straight now, and It would probably track even more straight with 500 000 fluid and sealed diff. But as mentioned above, I dont think thats the only issue. I mean people are running more powerfull setups than me with stock diff and stock diff grease...

What I can do next is delibritly mess with the left rear camber, and see If the pull gets worse or not. It could also be issues with the right rear end. I could also try to lock the rear diff temporarly to see if it pulls more straight. But this will be my last option because its messy with all fluids and stuff.


/tt3

[joe831]

Where did you buy those mamba stickers. I would love to have them on my rusty!

Email castle, I bought my system used and it didn't come with any stickers. Castle sent me a bunch for free.

I drilled a small hole in the rear end of the chassis and mounted the switch there. Looks like it's not too easy to reach for, but it's not that bad.
***

I had my switch kinda mounted like that and eventually dirt got in it and the switch failed and I had to cut it off.

[KeltiKrewser]

What are you using for grease in the diff?

I tried using High Temp wheel bearing grease in the diffs on my Merv when I ran out of 30k diff fluid once, and even thou the wb grease seems thicker, it was worthless in the diff and acted like an empty, open diff in a matter of minuets.

I would strongly suggest sealing the diff and running some 500k diff fluid. If consistency and repeatability are what you're after, it seems like the only logical choice to me.

[ttThree]

Thats true, I will seal the diff some time. I use castrol red grease. The diff seems tighter than stock, even after running a while. This was more or less a test to see how the rusty acted with thicker grease, and it helped a bit. But as mentioned above, i dont think the diff is the main issue because people are running more powerfull setups than me with stock unsealed diff.