gearing a new maxx?
 

running a 8xl on 4s lipo it looks to me like I'll need a huge pinion to get 40mph does this sound right?

Differential Ratio: 2.8461538461538463
Transmission Ratio: 1.83
Other Ratio: 1
Spur Tooth Count: 68
Pinion Tooth Count: 26
Total Voltage: 14.8
Motor KV: 2084
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0.0073
Spur/Pinion Ratio: 2.62 : 1
Total Ratio: 13.62213 : 1
Tire Circumference (inches): 18.06 inches (458.83mm)
Total Motor Speed: 30843.2 RPM
Vehicle Speed: 38.73 MPH (62.22km/h)
Effective Speed Rate: 2.62mph/V (4.2kmh/V)
Effective KV Value: 2084


phil

Those numbers look correct to me. It seems like a smaller spur would be ideal, so you dont have to run such a large pinion. That said, I dont think traxxas makes smaller spurs for the new emaxx, so maybe MOD1 revo spurs and pinions would be better (bigger selection of sizes).

yeah would def go mod1 just wanted to make sure the ratio sounded correct.. so the trans gearing is this much lower?
phil

Do you plan on going with the 2 speed kit?

I hadn't thought of it why? what are you running?
phil

I haven't ran mine yet. I'm waiting on the 2 speed kit so I can put together a special outrunner motor setup using the wide ratio gears from the kit.

Nothing against inrunners, I'm just caught up in experimenting with the 12 pole motors.

The reason why I asked if you were going with the 2 speed kit. To get 40mph with one speed is do-able, but also consider the additional torque you will have in 1st gear with the 2 speed. I believe the 2 speed kit will transform the new E maxx tranny into an automatic shifting monster. I can't wait. :yipi:

I ran some numbers for you using your motor and the stock pinion that came with your truck. Check this out. These are the wide ratio gears from the 2 speed kit.

Here's 1st gear.

Differential Ratio: 2.8461538461538462
Transmission Ratio: 2
Other Ratio: 1
Spur Tooth Count: 68
Pinion Tooth Count: 19
Total Voltage: 14.8
Motor KV: 2084
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 3.58 : 1
Total Ratio: 20.37247 : 1
Tire Circumference (inches): 18.06 inches (458.83mm)
Total Motor Speed: 30843.2 RPM
Vehicle Speed: 25.9 MPH (41.6km/h)
Effective Speed Rate: 1.75mph/V (2.81kmh/V)
Effective KV Value: 2084

Here's 2nd gear

Differential Ratio: 2.8461538461538462
Transmission Ratio: 1.16
Other Ratio: 1
Spur Tooth Count: 68
Pinion Tooth Count: 19
Total Voltage: 14.8
Motor KV: 2084
Tire Diameter (inches): 5.75
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 3.58 : 1
Total Ratio: 11.81603 : 1
Tire Circumference (inches): 18.06 inches (458.83mm)
Total Motor Speed: 30843.2 RPM
Vehicle Speed: 44.65 MPH (71.73km/h)
Effective Speed Rate: 3.02mph/V (4.85kmh/V)
Effective KV Value: 2084

In my opinion, this 2 speed setup will accelerate alot faster than the single speed setup geared for 40mph. It's hard to beat gears. :yes:

Ya know its weird, there is that area on the new tranny where it looks like an auto-shifting sensor will go. But, the new rx has four channels, and a 3 channel tx ( I think)- and there are also the mounting holes for a shifting servo on the chassis with the 2 speed kit. I dont know whether thi is going to be a simple 2 speed tranny like the old emaxx, or a cool auto shifting tranny via a special electronic item that controls the shifting servo....

now if it was an auto shift that would be great.. But truthfully nobody ever used 1st gear with the old max. (gorillamax 1 speed.) so why would it be different now,esp since its geared lower.
phil

True. The amount of torque on offer with a good BL motor in 2nd gear is enough to make a truck backflip, so using 1st gear would require super fine throttle control; I dont have that ability!

The advantage to an auto-shifting 2 speed is you can gear higher for more speed in second, while not getting to hot because it won't be overgeared in 1st.

so is it going to be a auto-shift 2 speed? I will def get one if so. they are listed for 55.00 in the parts list.
phil

Nobody really knows for sure yet. BUT, all indications point in that direction.

1. The lack of an extra shifting channel on the Radio

2. A sensor window in the transmission over the output gear - to detect rpm's in order to determine the shift point?

In my opinion, more gears is better. But I think one of the main reasons why so many chose to convert the original E maxx transmission so single speed was, if you shift on the go and the drive dog didn't fully engage before you hit it again. It would have a "come apart".

There was also alot of additional drag from how it was designed with 2 speed enabled.

The original transmission just wasn't tough enough.

True also. Shame I sold the spare parts from my tranny to make it a two speed.... hehehe.

well It might be awhile till I need it so. guess I'll wait. gonna run the titans for awhile longer.
phil

The tx is only a 2 channel isn't it? That's what some were saying on the traxxas forum.
I always liked having 2 speed in the old transmission, I still kept it 2 speed even though it was brushless and I raced it. The one speed kit seemed to me more like an upgrade for racing than bashing, since you only ever use 2nd gear for racing.

yeah its only a 2 ch TX .
phil

I always kept the 2 speed also. There's nothing like all that low end torque, especially if you're running in an area that just isn't large enough.

On a short track or in limited room, it's kinda hard to get those "long" legs out. Especially when getting stopped is an issue. :lol:

I always enjoyed crawling up and down rock piles or dirt piles. It's fun to see just what that 4wd will go through fast or slow. :yes:

just an FYI....
i used a 52t monster GT mod 1 spur and it bolts right up to the slipper. i am running 14/52 and its 35mph on the gps with no heat at all after a full 20 mins, perfectly racable.

also the new maxx has a 2ch tx and a 4ch rx(with 2 plugs for ch1), which seems a little odd

2 plugs for channel 1 would make sense if there was 2 steering servos, which there is, isn't there?

yes..they didnt just use a Y harness, the rx actually has 2 plugs

squee you are absolutely correct. i talked to a guy at the hobby expo and he said there are two slots for the servos in the receiver but both of them go to the same channel eliminating the need for a y harness.

what motor are you running in the truck? maximum ? what kv.
phil

ya its a maximum...
i weighed it today and its 9lbs 14oz rtr with the 4s pack
8lbs 12oz minus battery

makes sense the speeds you got with that gearing as the maxximum has a higher kv right around 2800-2900 from what I could find. so I guess I'll just gear up.
phil