RPM for 2200 with 6s
 

Hey guys/girls

I have a custom ride here and want to know if there will be wheel spinning upon take off and still not over heat things? Or will I have to gear so high inorder to keep RPM down that it will not peel out ?

10lb 1/5 custom losi direct drive, CD locked and rear locked, using a MMM, CC2200 and looking at buying a PQ 6s 6000 25c lipo 120 amps
I'm guessing a final ratio of 8:1 or so ? would be plenty for torque and speeds in 45+ 50mph
wheel base is 21"

Any recommendations here ?

Thank you very much

What size pinion gear are you using? You are currently set up for about 77mph (3.5vC, 2200kV, 4.5" tire). However you will still be able to spin your tires without fail. Just be wary of the jack-rabbit starts (with that gearing) or your MMM will say "Screw this!". :lol: Get it rolling a bit before you punch it.

have not run it yet,
tires are 5" tall hard rubber
not sure on what spur/pinion that will work best
but going to try a 49 spur and a 14p=11.5:1 . maybe go 17pin =9.5:1
also have a 45 spur

I ran 15:1 ratio with 3s on 1/8 wheels 4 3/8" tall street tires and it was awesome :intello:

Well I used the 8:1 final ratio to calculate those figures. That 15:1 final ratio will give you EXACTLY the range of speed you want on 6s (44+).

how did you get that? I have used brians speed calculator and made a huge Spur/Pinion guide for ratio and speeds.
49/11, but have not seen a Mod1 11 tooth ratio would be 14.7 36mph.

I'd like to know I could do 60mph without overheating.Any idea what ranges work without dangerous temps ?

Is 49/14 11.5:1 54mph ok ?

54mph will be fine.

any idea what the lowest or highest ratio would still be safe ?

I dont want to keep buying wrong pinions

Not sure, 50 mph gearing with the 2200 and 6s will be fine with the weight of vehicle you have with the sizr tires you plan to run. I am sure you could gear up to 60 or so without heat issues, although your lipo may get worked harder. Best to start with gearing for mid 40s and check temps. If you feel that is too slow gear up a few mph and then recheck temps... I have tons of pinions so that is my method...

First, I assumed a 4.5" tire diameter based on the picture. Then I assumed a WOT loaded voltage of 3.5vC (21V).

21V*2200kV=46200rpm.

46200/8=5775rpm (at wheels).

5775*60=346500rph (revs per hour).

4.5"*3.14159=14.137155" (tire rollout, inches).

14.137155"*346500=4898524.2075inh (inches per hour).

4898524.2075inh/12=408210.350625fth (feet per hour).

408210.350625fth/5280ftm (feet per mile) = (drum roll) 77.31256640625mph.

Did you get all that? Pop-quiz tomorrow...... :lol:

Yea, that would be the tru only way to know I guess. maybe the hobby hop will allow me to return some pinions.

Nitro, WOw, I'd like to learn how that is done, like how do you get loaded voltage
and how is this done without a ratio ?
Maybe it would work in the right conditions and only did one or two passes before things got to hot.
Why divide by 8? " 46200/8=5775rpm"

Very cool math :surprised: :lol:

Thanks. It's really simple if you think about it. Figure out the circumference of the tire and how fast it spins, then simplify it into the proper terms. I divided by 8 because of your final dirve ratio of 8:1. So to get how fast the tires spin you take the motor's speed and divide it by the final gear ratio.

Example: With your 15:1 ratio- (rounded numbers)

Motor speed: 45000 rpm
Gear ratio: 15:1
Tire circumference: 15 in.

Divide your motor speed by the final gear ratio and you get 3000 rpm. Multiply that by the tire circumference and you get 45000 in. per minute. Then divide that number by 63360 in. per mile and you get 0.7102 miles per minute. Times 60 give you your speed of ~42 miles per hour.

Use BrianG's calculator... no math needed :lol:

But- but- I like math! :mdr:

wow thank you very much, nice guy Nitro

it will be interesting just how close this will to the real thing, since there is drivetrain resistance/load and wind resistance

wih a ratio of 11 and a 5" tire I got 62mph, so I'm sure this equation will result to within 10 mph

I guess I'll just need to play around with ratios until the desired results come and with no heat problems

t

Using 3.5vC for the battery voltage accounts for most of the losses- air resistance, friction, and of course voltage drop. That figure should be a lot less than 10mph off.