Typhon Which has more top end? 13/43 or 15/42

[Niz55]

Any difference in speed between the two?

Thanks

 

[rotauq]

13/43 has a diff ratio of 3.308
15/42 has a diff ratio of 2.8

So it reduces your final drive with 0.5, which is a lot.
On a 34T spur a 20T pinion would become a 28T when it gets the 2.8 diffs

 

[Niz55]

Great thank you.

I thought for a second that the 13/43 was faster. Anyways I got them in the typhon front and rear.

Running 34/34 with castle 1650kv/MMX8S I hope I can hit 120mph.

 

[Niz55]

Well best I could do is 117.

Log showed 338amp and 66k RPM.

Would it be safe to up the pinion to 37T and spur to 29T?

 

[rotauq]

It's not smart to make make jumps in gearing.

338A is still safe. The mmx8s will register up to 400A and certainly can handle a little peak above as well.

66k rpm is not possible though, even on no load (33.6v * 1650kv) it should spin max 55k rpm. I can make many guesses, likely your datalog viewer is set wrong, please have a look at:
https://www.arrmaforum.com/threads/speed-runners-reading-castle-data-logs-and-esc-settings.37182/
Based on my calc 117mph on that gearing would have been ~29k rpm

So if these are the gears you have at hand, this is what speeds you could expect:
34S/37P ~125mph
29S/34P ~130mph
29S/37P ~140mph

I would be cautious, don't go to the 140mph config directly if you've never run these speeds with your rc car before. Your motor/esc will have no problem. But you and the car might. Suspension, tires, steering, all these things need to be optimal to safely drive that fast. And crashes at these speeds will hurt a lot. So proceed step by step, please

 

[Niz55]

@rotauq

Excellent information.
Thank you for taking your time and helping me out.

 

[Niz55]

Anyone know what is the smallest pinion that will work with 29 spur and stock mount?

 

[rotauq]

From the top of my head, 61T in total was the minimum (34P/27S) i could fit. I am not running the stock mount anymore so i could be wrong.
Based on that it would be 32T, 33T will definitely fit.

 

[Niz55]

@rotauq

Best I can do is 120mph with 34P/29S. Maybe I need a cap pack??

But anyways I am going to go with 8S setup.

Thanks again for your help.

 

[rotauq]

A cap pack wont make it run faster, just cleaner what could make a few rpm's in difference. If you logs show more than 1.5v ripple a cap cap would be good.

You have the motor/esc/gearing to go a lot faster, so what is holding you back must be something else.
Just naming a few potential causes:
too short distance, aggressive throttle finger, friction in the drivetrain, overtightened wheelnuts, average batteries, high temps outside, aero/drag, ride height to low/high

 

[Niz55]

Not sure why the hell this thing is pulling almost 400 amp?? Everything is perfect on the car. Bearings are new ceramic. Car drives absolutely perfect and straight. I even measured the resistance on the esc cables and they were 0.5ohms for both.

I am assuming the esc is not capable of my setup.

Battery I used was panther 6s 5000mah.

 

[jondilly1974]

Not sure why the hell this thing is pulling almost 400 amp?? Everything is perfect on the car. Bearings are new ceramic. Car drives absolutely perfect and straight. I even measured the resistance on the esc cables and they were 0.5ohms for both.

I am assuming the esc is not capable of my setup.

Battery I used was panther 6s 5000mah.

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If those RPM values are true, you may be overgeared. You should be hitting somewhere in the 40k range when maxed out. This shows 27k RPM. Are you choosing gearing in the Castle app? It should be left 1:1. Make sure to select 1650kv and 4 pole.

 

[Notoriousone]

Your speedrunning, right? In your screenshots you have drag brake enabled. Maybe disable it unless running in a vey short area where strong brakes are needed? Drag brake gives you peace of mind if you run out of radio range, but if you get off the throttle even a tiny bit it kills all momentum

 

[Danyrc]

Your speedrunning, right? In your screenshots you have drag brake enabled. Maybe disable it unless running in a vey short area where strong brakes are needed? Drag brake gives you peace of mind if you run out of radio range, but if you get off the throttle even a tiny bit it kills all momentum

Drag brake should only works when throttle is in neutral. On the other hand Punch control is set to 90% which limits the acceleration, default is 0% (disabled) I would lower that number.

 

[Sloclone100]

A cap pack wont make it run faster, just cleaner what could make a few rpm's in difference. If you logs show more than 1.5v ripple a cap cap would be good.

You have the motor/esc/gearing to go a lot faster, so what is holding you back must be something else.
Just naming a few potential causes:
too short distance, aggressive throttle finger, friction in the drivetrain, overtightened wheelnuts, average batteries, high temps outside, aero/drag, ride height to low/high

I did not read the entire post but were the diffs mentioned? The front and rear should be locked (either shoe-glued or some other adhesive), or buying new diffs. And the center diff should be locked as well.

Sorry if this was a repost.

 

[rotauq]

I did not read the entire post but were the diffs mentioned? The front and rear should be locked (either shoe-glued or some other adhesive), or buying new diffs. And the center diff should be locked as well.

Sorry if this was a repost.

Center diff locked is essential for speedrunning. Not for gaining more speed but to keep it on the road. It will flip at high speed.

Front/rear is not mandatory, some top guys even run stock fluids (if everything runs synmetric low friction)
Very thick fluid or completely locked does reduce some friction and could prevent certain type of crashes that can occure.