G-maxx entering ISC event in fontana CA

[Rivermaxx]

http://www.rc-isc.com/index.html
I was thinking about entering my g-2 maxx into this event . It will be geared high lightened lengthened and narrowed. I was wondering if you guys could help me out with your knowledge since I am pretty new at this lipo brushless thing. The record as of now is only 58 mph and I pretty sure I can break it. The open wheel class is really small so there is not much competition.

First off what kind of brushless power and batteries do you recomend? I have a used 2 times revo take off 2200kv castle neu and mmm and 2 zippy 3s 5000mah 30c lipos. This truck is insane on 6s and uncontrolable with the regular proline tires balloning so bad. I am planning on using the 3906 tranny with g-maxx single speed conversion on it and UE idler or going direct drive straight to the diffs. I would have to have a custom motor and mount made for that though and I dont think I have time. As most of you know the g-maxx chassis has a real low cog (lower than a revo) and should be a good canidate for this build. I am going to narrow it with some old rpm arm I have had laying around and cut them down to lighten them. I have UE 8 and 6 spider diffs but I was thinking the stock traxxas 3905 might hold up if I dont punch it out of the hole. I am going to get rid of any and all extra weight. I am working on having some special foam tires custom made for use with the new proline 4" vtr wheel that recently came out. Thats all for now post up your thoughts

[_paralyzed_]

dont use 3905 diffs, 6 or 8 spiders will work.

use the 3906 tranny, double the stock motor mount plate and run twin MMM 2200 systems on 6s. Robinson Racing Monster GT spur (bolts right on and is Mod1) and Mod1 pinions. Twin 6s 5000mah(or more) 30c(or more) batteries (one per system)

use a tire with a straight groove around the circumference (or cut your own) and wrap and glue high tensile fish line around it to stop balooning (your foams may hold up? iffy?)

use a gyro on the steering to help you drive straight.

stiff low springs..............

Do it up!

[suicideneil]

Dual MMMs or a single HV esc & and a 1521 neu would be my choice- the same setup as used by that 90mph BL Erevo....

[Rivermaxx]

I allready have the double stock motor mount and I could get another MMM setup I think the 2 6s batterries will be too heavy. Unless your thinking it will help it stay on the ground better.Whats the biggest mod 1 pinion I could get??? not to mention is the plastic gear that still in the tranny going to melt? I am working on getting custom made foam tires put on vtr wheels no rubber and fishing line for me. That 91.2 mph revo had a mmm with a neu 1.5d 2650kv motor. Whats a gyro ??? I have heard of the but exactly what does it do? Keep the ideas coming guys.

If you guys want to see pics of my finished silverback build they are in here http://www.rc-monster.com/forum/show...861#post312861 . Obviously I am not going to run 3mm ti skids or titanium bumpers. I am going to use 0 or negative offset wheel and narrow (old style) rpm arms. I am probably going to use revo shocks with a duh engineering titanium short monster gt tower. It going to be as low as I can get it. I need to figure out what body to run also. Any sugestions? Remember It needs to be arrowdynamic and possibly have downforce.

[suicideneil]

Gyroscope= keeps you heading in the same direction, even when wind or outside forces try to alter your course (hooks to the steering servo basically) without you touching the the steering wheel.

I would keep the Ti skids in place, they will be a life safer should something unexpected happen and you slam into a wall at max throttle.

As for the body, the Proline slipstream gets my vote as one of the most aerodynamic shells for an MT, otherwise a truggy shell of some description + big ass rear wing.

A pair of 6s lipos wouldnt be that heavy, got to remember that one typical 2-3s lipo pack ways half that of a 6 cell nimh pack, and I've seen guys running 18 of those cells in dual BL maxxes back in the day.

As for your tranny issue, you can always get this great chap to custom make you the required output gear in aluminum, to fully beef it up:

http://www.rc-monster.com/forum/showthread.php?t=21856

Mod 1 pinions from Mike go upto 25teeth, beyond that KershawDesigns sell Acetyl plastic pinions with a brass insert upto 38teeth, though I would rather get something from SPD-SI custom made then use a plastic one.

[Rivermaxx]

Hey Neil thanks for coming in on this one your knowledge will be greatly appreciated. I have extra thinner 2mm titanium skids I will be using, quite a bit lighter then the 3mm thicker ones. Proline slipsteam even sounds fast, I will check it out. 25 teeth aye let me go check the calc for speed with that gearing. edit I just ran the calculator with the 51 tooth spur through a g1 tranny and 4.5 inch tire its not fast enough.Wheres the monster center diff when I need it The tires are killing me because the biggest good rim I can get is the new vtr wheels with a .300 thick peice of foam rubber wraped around it. The foam shouldnt be any bigger because of centrifical force exerted on it. At least that what I was told. How about buggy wheels with foams with a direct drive setup. I need a motor that the shaft come out on both sides. Not to mention a lower gear in the diffs. With the calc I get speeds to ~145 mph with that set up .
You guys think I could run 1 motor in the front on 6s and one in the back on 6s direct drive? I can buy another complete mmm set up for less than it would cost to buy a special neu motor.

[suicideneil]

Nay, you would require a large outrunner for any kind of direct drive setup- Linc & Sike are the best guys to discuss that with. Running buggy wheels would be a no-no too, have to be MT sized rims, although 1/5 TC rims would be interesting- depends what the rules say about that kind of thing as some events are cracking down on using parts that arent designed for that specific class of vehcile (like TC wheels and a TC body on a Wheelieking for example... ).

Curious though:

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1.7222222222222223
Other Ratio: 1
Spur Tooth Count: 51
Pinion Tooth Count: 25
Total Voltage: 22.2
Motor KV: 2200
Tire Diameter (inches): 6
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.04 : 1
Total Ratio: 11.62103 : 1
Tire Circumference (inches): 18.85 inches (478.78 mm)
Rollout: 1.62:1
Total Motor Speed: 48840 RPM
Vehicle Speed: 75.02 mph (120.51 km/h)
Effective KV Value: 2200
KT constant: 0.61 oz-in/A

A 51tooth Mod1 spur and a 25/26tooth pinion should be plenty to push in excess of 70mph, just dpends if the motor will foul the tranny or not. If it does, you can run a second motor mount spaced off the first with short posts, then flip the motor across so that it wont interfer with the tranny.

Kinda like this:



Not pretty, but it will allow for much taller gearing without tranny clearance issues.

http://www.kershawdesigns.com/

[Rivermaxx]

Actually running buggy wheels is allowed since I will be running against any open wheeled 4wd vehicle from 1/10 to 1/4 scale. I will be competing against them all. I think they understand the issues of the tires not holding at speed. The problem is the foam tire cant be thicker than .300 from the rim to the outside edge (at least that what I was told) because of centrificle force. So with the gearing you stated and a 4.6 inch tire the speed goes down considerably. Tires diameter make a big difference with your gear ratio. I come up with 57mph with 4.5" tires and 25p 51s respectively.That aint going to work!!! I need to get a smaller spur or bigger pinion.

My idea is to run 2 esc's and 2 castle neu 2200 kv on 6s each, one running the front diff and one running the back diff separatly back to back in the chassis. Just an idea I dont know if it will work. I come up with 175 mph with my set up but I have no way of inputing 2 motors. Anybody have any ideas how this can be done with out breaking the bank too bad.

[suicideneil]

4.6" is tiny, I'd think about something atleast 5.5" really- stick a piece of drainpipe over a normal MT rim, then stretch a rubber tube over that...

As for the motors, you cant hook an inner to a diff, they just dont develop enough power or torque to turn such a high gear ratio (only reduction is the diff)- even with one motor for each axle. Big outrunners like Turnigy or Holmes hobbies sell would be the ideal thing, but like I said, its a tricky thing to choose the perfect one as you can adjust the gearing, only by using smaller or larger wheels & using buggy or truggy diffs.

All said and done, there are MT foams available from a few places (Imexrc.com), or the HPI Phaltlines work well if you tape the insides and glue them to the rim well.

Using larger pinions has the same effect as using larger wheels after all, so it would be easier to find the right sized wheels that wont fly apart, rather than custom ordering massive pinions.

That, or find higher kv motors to use- the castleneu 2650s would still work fine if you have two of them in one truck....

[Rivermaxx]

Originally Posted by suicideneil

4.6" is tiny, I'd think about something atleast 5.5" really- stick a piece of drainpipe over a normal MT rim, then stretch a rubber tube over that...

I know but so far thats the only really good option. I am going try to glue a bigger donut on a plastic wheel as I do have a set that are on aluminum wheels but they were not glued properly. The drain pipe idea has been done and it didnt work plus its way too heavy.

Originally Posted by suicideneil

As for the motors, you cant hook an inner to a diff, they just dont develop enough power or torque to turn such a high gear ratio (only reduction is the diff)- even with one motor for each axle. Big outrunners like Turnigy or Holmes hobbies sell would be the ideal thing, but like I said, its a tricky thing to choose the perfect one as you can adjust the gearing, only by using smaller or larger wheels & using buggy or truggy diffs.

I could be wrong but it seems like they have plenty of torque to me especially with 2 15151y 2200 kv on 6s. I would get the lowest gear availible also and run really small tires (buggy 4") to lower the final drive even more. Dont forget the super high gear ratio and the required torque is being shared by 2 motors, 2 esc's and 2 6 s batteries and not one. I will acelerate slowly dont want any wheelies question is will it work. I punched the number in the calc and I got this: I put the amperage draw @ 100 amps not sure if that was right. Its 5 mph faster without putting anything in the amperage section. Remember this is only for one motor.
Differential Ratio: 4.3
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 1
Pinion Tooth Count: 1
Total Voltage: 22.2
Motor KV: 2200
Tire Diameter (inches): 4
Tire Ballooning (inches): 0
Motor Current Draw: 100
Motor Coil Resistance: 0.006
Spur/Pinion Ratio: 1 : 1
Total Ratio: 4.3 : 1
Tire Circumference (inches): 12.57 inches (319.19 mm)
Rollout: 2.92:1
Total Motor Speed: 47520 RPM
Vehicle Speed: 131.51 mph (211.25 km/h)
Effective KV Value: 2140.54
KT constant: 0.61 oz-in/A
Motor Torque: 0.32 ft-lbs
Final Torque: 1.38 ft-lbs
Final Power: 2220 watts (3 HP)
My g-maxx is going to pretty light also, so if one 2200 kv in a erevo can go 89 mph shouldnt double the hp double the torque double the volts (kind of) go over 100mph.

Originally Posted by suicideneil

All said and done, there are MT foams available from a few places (Imexrc.com), or the HPI Phaltlines work well if you tape the insides and glue them to the rim well..

I have read the imex dont work at speed the foam gets thrown of the wheel. Hpi phatline is a viable option not sure if just tape will work but OverrevO the guy with the 91.2 mph erevo glued 40# test carbon fiber fishing line on the groove in the tires. Heres a pic:

Here some pics of the 5.100 tires I have. Whoever mounted them used the wrong glue so I am going to dismount them and try to glue them on plastic wheels with good ca glue.The biggest issue being the foam is to thick and heavy so when I am going 75+ will the centrifical force throw the donut off the wheels.

Donut that came off the wheel on the first run.

Next to a proline mtr about .500" difference in diameter.

Originally Posted by suicideneil

Using larger pinions has the same effect as using larger wheels after all, so it would be easier to find the right sized wheels that wont fly apart, rather than custom ordering massive pinions..

I agree with you there I could do a revo conversion slipper setup like yours and run a 36 tooth spur with a 25 tooth pinion (same gearing as the 91.2mph erevo). Heres what I get on the calc with 5.5 tires which are phaltline size.
Differential Ratio: 3.3076923076923075
Transmission Ratio: 1.7222222222222223
Other Ratio: 1
Spur Tooth Count: 36
Pinion Tooth Count: 25
Total Voltage: 22.2
Motor KV: 2200
Tire Diameter (inches): 5.5
Tire Ballooning (inches): 0
Motor Current Draw: 100
Motor Coil Resistance: 0.006
Spur/Pinion Ratio: 1.44 : 1
Total Ratio: 8.20308 : 1
Tire Circumference (inches): 17.28 inches (438.88 mm)
Rollout: 2.11:1
Total Motor Speed: 47520 RPM
Vehicle Speed: 94.79 mph (152.26 km/h)
Effective KV Value: 2140.54
KT constant: 0.61 oz-in/A
Motor Torque: 0.32 ft-lbs
Final Torque: 2.63 ft-lbs
Final Power: 2220 watts (3 HP)
It says ~88mph with the 5.100" tires I allready have.
It says ~77.5 mph with the 4.5" tires.
It says ~69 mph with the 4" buggy tires.
Thats smaller spur looks like the route I am going

Originally Posted by suicideneil

That, or find higher kv motors to use- the castleneu 2650s would still work fine if you have two of them in one truck...
.

Spinning a 2650kv on 6s is right on the borderline of 60000 rpm max not sure if I want to push it but it is a possibility.I think the 25 tooth pinion 36 tooth revo spur conversion is moving in the right direction though. Thanks neil for all your input you have got my brain turning now. lol
This is the chassis I am going to use as I am going to swap it with a g4 chassis and use the g2 for the speed trials.

Its ashame I just finished this truck.

[Rivermaxx]

I just talked with john @ bsr and he is going to make me some custom shoes that should be about 5" in diameter. Is going to cost me around $120. But I got to do what I got to do. Thanks for all the help. As far as the gearing I have a 36 tooth mod 1 spur with a 25 tooth pinnion. This is what I come up with this @ 3 volts which is what Nic Case told me to use on brians calc :BTW I love this calc brianG thanks! !
Differential Ratio: 2.8461538461538462 Traxxas diffs UEs are too low
Transmission Ratio: 1.7222222222222223
Other Ratio: 1
Spur Tooth Count: 36
Pinion Tooth Count: 25
Total Voltage: 18
Motor KV: 2700 neu 1.5 d
Tire Diameter (inches): 5.
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.004
Spur/Pinion Ratio: 1.44 : 1
Total Ratio: 7.05846 : 1
Tire Circumference (inches): 15.71 inches (398.98 mm)
Rollout: 2.23:1
Total Motor Speed: 48600 RPM
Vehicle Speed: 102.42 mph (164.52 km/h)
Effective KV Value: 2700
KT constant: 0.5 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...


Not sure if I want neu 1515 1.5d (above)or 1521 1d motor (below):

Differential Ratio: 2.8461538461538462
Transmission Ratio: 1.7222222222222223
Other Ratio: 1
Spur Tooth Count: 36
Pinion Tooth Count: 25
Total Voltage: 18
Motor KV: 2900 neu 1521 1d
Tire Diameter (inches): 5.
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0.003
Spur/Pinion Ratio: 1.44 : 1
Total Ratio: 7.05846 : 1
Tire Circumference (inches): 15.71 inches (398.98 mm)
Rollout: 2.23:1
Total Motor Speed: 52200 RPM
Vehicle Speed: 110.01 mph (176.71 km/h)
Effective KV Value: 2900
KT constant: 0.47 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

Which route would you guys go as far as motor? Not to mention what batteries too use for this short blast high speed run. I need to figure out a aero dynamic body and get some spare parts just in case.

[suicideneil]

I would go with the larger motor, should help with the topend where you really need that extra power to overcome drag. You'll need some gert big lipos though, thats for certain.

As for a body, either a nice lowprofile truggy item, or the proline slipstream- JConcepts have some very nice items.

[Rivermaxx]

I am thinking the 1521 1d is going to be an amp hog and the cc mmm wont handle it. I know the 1515 1.5d will work especially in a lighter truck, not too mention its alot cheaper than the real neu. I could buy 2 of them for the same price but then again I need another esc.

[mkrusedc]

I posted this a while back. For all your gearing needs. They will custom make gears to your specs if needed.

http://www.rc-monster.com/forum/show...t=custom+gears