Spiral cut or straight.

[MFM]

Driving myself a lil loopy trying to figure out why some arrmas have straight cut input and ring gears while others have spiral cut!! I’m messing around w gear ratios and final drives trying to get the most bulletproof and reliable differential set up. The infraction, limitless, felony , and typhon all have straight cut ring and input gears. They use a 43 or 42t ring gear matched w a 13,14,15t input gear. The bashers including EXB seem to be running spiral 43/10.
so what’s the advantage of having spiral cut vs straight? Can someone plz educate us!?
thanks.

 

[888henry]

Well from my understanding of 1:1 cars, they use spiral cut pinion and ring gears for differentials. With that being said I think that spiral cut gears would be the best option to bulletproof your drivetrain as they increase the surface area where the ring and pinion meet. Take this with a grain of salt, I don't have first-hand experience with those diffs. (that's a diff from a 1:1 car, notice the bevel/spiraling)

 

[suchtragedy]

Basically spiral cut is stronger due to more mating surface but very slightly less efficient in terms of energy loss, also is quieter. For RC applications the tolerances of straight cut is fine most of the time and it's cheaper to manufacture.

 

[jondilly1974]

Straight cut are more efficient at transferring all the power but are easier to strip, so that’s why only cars with smaller or lighter tires use them. Spiral cut gears are stronger as more teeth have contact at a given time, but this robs some of the power. Spiral cut are used when max strength is needed. Oddly they are more quiet too, so that’s why most 1:1 cars use them. Race cars will have straight cut gears for efficiency though.

 

[MFM]

Makes sense. I was considering changing the input (pinion) and ring in my Mojave to get most speed but I can’t find any spiral 13t only the stock 10t. Oh well. Good info tho. I may just upgrade em to the gp4 EXB

 

[Twitchfast]

After having had the same thought process, I personally just stuck with my straight cut gears because on the 1/8th scale models, the surface area increase due to (what little spiral there is) is negligible.
The 1/5th scale cars have some nice spiral cut gears, just a shame you can't fit them in the 1/8ths
The only way I snapped a tooth was a 4 wheel burnout when the car decided to hop, 8s + 49pinion/19t spur at full speed on molten GRPs.

 

[jondilly1974]

The EXB gears have a much larger contact patch with the ring and pinion, in addition to having more pitch to their spiral cuts. These are changes when compared to the RTR diffs that should help them withstand more power from larger motors.

 

[MFM]

The EXB gears have a much larger contact patch with the ring and pinion, in addition to having more pitch to their spiral cuts. These are changes when compared to the RTR diffs that should help them withstand more power from larger motors.

And thus the answer to my final question lol. U know what I got coming together in the lab;-).
gonna toss my rtr built diffs in the talion, then build gp4’s for the “worlds fastest Mojave” hahaha.
after doing some more research I found the Team Associated and some mugen diffs to be similar in size. Hmm. Wondering if theirs are better..or will even work.. they have an avail 13t spiral....
ugh. So many tweaks and adjustments still to be made!!
PPS stuff “out for delivery” should be arriving any moment;-)