Top speed race class
 

Hey guys here locally they are doing a top speed challenge in mid Feb. and they have different classes. The new class they added for this year was a monster truck class, and minimum weight limit is 10lbs. Also they put a battery limit to 3S lipo or 10cell NiMH....no MAH limit and also no amount of motor limit, so 1, 2, or 3...etc if you can fit it. Tires and body have to be off road tread and stock body. Should be fun....now million dollar question is...what to run? I have my 3905 truck with dual VXL's which I will enter it, but my 3906 is still stock . What ESC's and motors should I be going with on it for just top speed runs?? I'm am thinking 65-75mph is what will be needed. I have some extra springs that I will cut to lower the truck down LOW, and then try to lower the body mounts low as well. The speed freaks let me know.....


Just remember the battery limit is 3S lipo or 10cell NiMH....no MAH limit

Good luck getting any 10lb vehicle to 60+ mph on 3s. Basically, you're going to have to get a higher kv motor than is typically used in a monster truck. Along with that, expect a large current draw and lots of heat. I'd start by looking into a high current ESC and a Neu 1515 or Feigao 540 XL motor somewhere in the 3000kv range.

I do have to say that 3s really is a pretty dumb voltage limit on a 10lb vehicle.

4s would be much more interesting and open up alot more options

Now remember guys, jthe 3S limit is PER motor. If you run 2 or 3 motors...or more, each one can get 3S or 10cell power to it.

In that case, maybe something like dual MM 5700's on 3S each?

Your still going to have to run a high KV motor and they are both going to want a lot of current to reach those speeds.

Maybe 2 Feigao 9l as well.

You didn't say that in the original post...that changes a lot of things.

I'd go with something like twin Feigao 540 7L's on 3s each.

Actually, MM7700 will tolerate 3S for short bursts.

It is going to be REALLY hard to reach 65mph on 3S with a truck, extremely difficult. I would say 50mph would be doable. Anymore would require alot of R&D and multiple ESCs on multiple motors [translated into EXPENSIVE!!!]

Matt

Well my 3905 has dual VXL3's and dual Velineon's in it. I am going to upgrade my 3906 as well with whatever combo you guys think will work best. Twin mamba ESC and twin 7700's or 5700's sound good? Of course on 3S lipo's max....

do you have unlimited room to do it? you could drop the chassis as low as possible and run a set of jumbo kong tires ;)

With a 3S limit, I would run a pair of KB45's with the appropriate KV. Just make sure your ESC and packs will handle the current they will draw.

I'll also throw in a suggestion that you look into using the new Pro-Line premounted LPR tires/wheels. You'll get far less ballooning than regular MT tires and they're much lighter as well. You'll just need to have 17mm hexes on whatever you're planning to run though.

http://prolineracing.com/products/html/LPRpremount.html

According to Brian's speed calculator, 65+ mph should be possible with 2 MM5700's. Also, tire ballooning will increase his top speed, so I don't think you should try to minimize it.

Gearing up is a much better option for hitting top speed than to desire tire ballooning IMO. Trying to keep a truck tracking straight with pizza cutter tires is no easy task for the driver or their steering servo having to fight such a large inertia.

i would definatley go with dual mambas and dual 7,8,or 9Ls for motor the L motors would tolerate being geared up alot better than the little mamba motors. Run one of those on 3s and gear it to the moon with light as possible tires.

what about dual 6900's?

The mamba's are no good for such a big vehicle. You need as a minimum L-can motors. Go for the Foam tires. Imex has them. Pizza cutters are very difficult to control and are very dangerous. A 10Lbs vehicle going 60+ mph will cause serious injuries and damage, when control is lost.

i think it said he had to run offroad tread tires = no foams or slicks

That's just dumb and dangerous if the rules state to only run offroad tires in a speeding Monster Truck. But if that's the case, just belt the tires with tape and stuff it with the stiffest foam available. Ballooning tires are cool when bashing, but in a real high speed race (even in a controlled enviroment), is just asking for trouble.

On 3S which would be the most powerful then with twin setup?? The mamba's or the 7, 8 or 9L's. How about the XL's or Neus's??? Money is no concern...I just want to be able to place near the top...lol.

Correct, that is just the rules.....

I am going to run some Imex tires with beadlock wheels to keep them on the rim. Also I haven't been able to find a stiff enough foam. They are 6.7" diameter tires.

It wouldn't be such a bad idea to use a really thin film of RTV on the beads of the tires when using beadlocks. Let is dry overnight or longer before use. It will have a stronger hold that way. I can rip the tires of my beadlocks with one pull of the trigger.

Yeah I will try that, but I really need stiffer foams for these things. That will help also....but have had a heck of a time finding them.

If there is a Joan's fabric store(or such) around you, they have some really stiff/firm foams available which you can cut up as foam inserts. I have used some of their foams when I had built my own couch for the house. Good stuff.

Hmm I'll try that.

About the setup for the 3S's how do the setups I posted about stack up??


Would I be better off with twin mamba's or the 7, 8 or 9L's. How about the 7, 8 or 9XL's???

XLs will have lower RPMs and require even more gearing - with two motors I think the 7L 3500kv would be a good bet...

Or how about dual Novak HV 4.5s...

Looking at the 3500KV's they seem to be the same as my current Velineons which are 3500's which are on my 3905 truck. My 3906 truck with the two 7L's , would it really be anymore powerful then the two Velineons on 3S's?? How would 6L's do they are 4096KV's and seem to have a little more grunt then the 7L's?? The RPM's though are a little over what the motors are rated though...

You could swap to ceramic bearings which would get you some more RPM - 6L might hold up.

However the L is much bigger than a V motor - which is less torquey I believe than an S.

dual 7Ls on 3s would rip

Would the mamba max controllers be the best to use?? Or will the VXL3's be the ticket for the 3S limit? The mamba's though will take up to 4S correct?

I looked for the 7L's for pricing and don't see them listed. I am ready to order.....

I would have to disagree. Two Mamba's in a MT will be more than enough.

I would go for either two MM5700 or 6900 setups using Komodo LP tires. There lightweight and won't balloon. If moneys no object though, maybe go with two Neu 1509's with a couple MGM 9012's.

Also, there is no reason to run ceramics. I have run stainless bearings up to 90,000 RPM without problems. The ceramic bearing thing is a bunch of hype with very little basis. Focus on getting as much power to the wheels as you can.

Matt

What is the distance that this "topend" should be achieved in?

Tashpop should be here giving you ideas how to get the topspeeds in a MT. He has been showing up at our drag race Test and Tunes with his beast and his goes fast.

http://i189.photobucket.com/albums/z...n/DSCF2101.jpg

Line of sight for a 10th scale car is about 1000 feet. I try to get my car to max out in about 800 to 900 feet.

Matt

Total distance is 1320ft if you need it.

Well whoever can chime in to get me squared away would be great. I am ready to order right now and have my debt card in hand....lol. This event will be here before I know it so I need time to test with different spur pinion combos. I just ordered everything from 20T-24T and 62-52 so far for spurs.

AAh, so it's a true quarter mile race. So do what Modman suggested, about reaching your "max" speed at 800-900 feet. You better have some beefy 3 cells man.