I think the documentation on the telemetry and the speed calculation is a broad overview at best. Is there a Traxxas employee that can weigh in on this? The question is if you don't change your garage settings after changing spur and/or pinion will that affect your telemetry speed?
I will try to test this, but don't have a radar gun handy to give this a go. I was figuring to test lock the model and start with factory gearing 46/14 and Make sure the garage is setup for that gearing. Make a speed run trying not to spin the tires and capture the top speed with radar and telemetry. After which change the pinion 46/34 but don't update the garage the speed control should keep the car from going faster then 50 mph on telemetry so also capture that high speed pass with a radar gun. Lastly change the garage settings and do the previous test and then compare the data. Anyone in a warmer area with radar gun that can do this?
Last edited by snapshot4; 02-29-2012 at 07:30 AM.
Ducati777 I get it now so because the RPMs are measured on the shaft vs the motor the spur and pinion gearing makes no difference. So the only ratio to use in the calculation would be the diff ratio. That makes sense but I still can't get the math to work out.
Are the RPMs in the dashboard motor or shaft rpm? If they are motor then the gearing ratio would affect the motor rpm calculation however if it is shaft then the math just doesn't work out for the speed calculation.
From my understanding, it's the motor rpm. I don't know why different gear inputs affects actual speed though. My only guess would be that it calculates motor rpm and then speed from there. Doesn't make sense why it would, but who knows.
All I know is I corrected my settings and it went from being about 10 mph off to 1-2 mph off from gps.
I did do some testing and changing the gearing in the app garage affect the RPMs not the speed. My guess is that the speed is based of the shaft RPM (the actual count) and the motor rpm in the dashboard is calculated using the gearing ratios.
Clear as mud to me now.
Thanks Dadx2mj for chiming in.
and now we return to the powers speed thread already in progress.....
Nice run powers telemetry is good enough for me that thing was moving.
Oh man, I started reading the first page and at the bottom realized it was 1 of 3! Regardless awesome control, as others have said - it's great to see someone who is capable of controlling themselves to allow themselves to control the car!! It's what makes racing these things so fun, it's not finding the car's limit it's finding your own and staying within it. This video proves you've done just that, *cheers!
The rpm is a backwards calculation off center shaft rpm, not a true reading from the ESC.
What kills me is the ESC knows the exact RPM, there's a protocol already established to send that through telemetry, and yet Traxxas hasn't released the update!!!!
Castle finally did their update, so at least we can link, but Traxxas hasn't updated the radio...
Regarding the math... my car goes 70 mph geared 21.46. (i've seen higher, but lets just call it 70)
70 mph is 369600 feet per hour, 6160 feet per minute, 73920 inches per minute.
Wheel travels 13.5 inches per rev, so they turn at 5472 rpm
Center shaft is turning at 15595
geared 21/46 motor must be turning 34160....
Well its a 1650kv motor, at 22.2 volts it should theoretically turn 36630....
Sounds pretty dang close to me.
But see how the pin/spur comes after we calc the shaft rpm? Shaft rpm at 70 is going to be the same regardless of pin/spur combo. If we change tire size to... say the 3.8 inch ebay slicks I like on my other cars.... the telemetry will read 70, but the car would only be travelling at 61.8 mph....
Last edited by ducati777; 02-29-2012 at 03:07 PM.
lol.... its ok ponie, people ask the same question repeatedly on these forums.
But I understand... I'll keep the thread jacking to a minimum.
Makes sense....I did some speed runs today and used the RPMs to calculate speed and it worked out. So the world is back to being round again, it drives me nuts when the math doesn't work out . Thanks for the info.
Awesome video Powers! I'd love to get an X0-1, but I'd have a hard time finding space running it. A lack of space and close neighbors are why I sold my 3.3 Revo. Now I have a super-slow Summit, but I love it!
Last edited by bigjaybo77; 03-01-2012 at 10:19 PM. Reason: Typo
i agree i love this car ive had the erbe geared to the moon but to me its like the acceleration on this thing is unbelievable.
just installed the 19 tooth pinion and tried it out in a small space in front of my house and it quickly got up to 61mph