gearing a new maxx? - RC-Monster Forums

phildogg · **gearing a new maxx? -** 12.29.2007, 04:33 PM

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

suicideneil · 12.29.2007, 04:39 PM

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).

phildogg · 12.29.2007, 04:52 PM

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

sikeston34m · 12.29.2007, 05:26 PM

Quote:

Originally Posted by phildogg

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

Do you plan on going with the 2 speed kit?

phildogg · 12.29.2007, 05:31 PM

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

sikeston34m · 12.29.2007, 05:43 PM

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.

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.

suicideneil · 12.29.2007, 05:57 PM

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....

phildogg · 12.29.2007, 06:12 PM

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

suicideneil · 12.29.2007, 06:18 PM

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!

squeeforever · 12.29.2007, 06:32 PM

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.

phildogg · 12.29.2007, 06:36 PM

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

sikeston34m · 12.29.2007, 06:50 PM

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.

suicideneil · 12.29.2007, 07:15 PM

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

phildogg · 12.29.2007, 07:53 PM

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

Patrick · 12.29.2007, 10:49 PM

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.