scooter VS ATV showdown!

[miniquadtuner]

Hey Scooter Guys, us Mini ATV tuners are calling you out for a drag race show down!

In case you don't know, mini ATV motocross is a big national sport, and we use the same type motor a lot of you guys do - minerelli's, Jog 2T in 50, 70 and 90cc - and we build them to the hilt using most, if not all of the same hop up parts you do.

A lot of us mini ATV tuners watch the scooter forums, but not all road racing set ups work well for MX, but scooter drag racing, well that is interesting! the start of our race is basically a drag race to the first corner - 250-500ft or so, then race on.

I'd be interested, for fun and joint learning of course, to see if anyone in the southeast (georgia would be best) would want to drag their scooter against our ATV in an exhibition race.


some specs on our 50cc modified racer:
50cc, minerelli motor
RWHP - ~10HP
max RPM 14.5k
vehicle weight ~250lbs
0-125ft - less than 4 seconds is all I am saying
0-125ft max MPH -? greater than 30mph would be a good guess

Attachments:

[Rebel]

I'm sure some guys would go for it. You might get in touch with the NASRA guys and see if there is a possibility of a joint event. I'll let Jeremy know about this challenge.

[miniquadtuner]

Cool deal. I saw the twist and scoot event in IN, but a bit of a haul for us as we are currently in our national season and hauling already every other weekend. will be in MD next sat for a race!

Can let the promoter group know our rider, on team Hetrick is the 2010 AMA sanctioned ATVA 50cc national champion. not that it matters, but promoters like that sort of thing. Also, spoke with our race team manager, Rich Hetrick from Hetrick racing and he might be interested in getting some of their 70cc and 90cc bikes out for this too. some of those monsters are making north of 25HP!!

[Enviromoto]

I dont know I think you guys would run out of gear getting to 660ft.

[miniquadtuner]

not sure when we'd run out of gearing really, but that would be the deciding factor for sure. what's an average top speed for a 1/8 mile run for a 50cc scoot? right now, our final drive,tranny and CVT setup max theoretical speed is about 50mph. I have a radar gun, but only use if for short sprints, not top speed. my guess is we'd hit mid 40 mphs without much change in our gearing as it stands. I could setup final drive pretty easy to get max theoretical to mid 60's, and get ground speed up to low 50s I bet, but not sure how that would effect our launch / take off.

Here is a video from our latest race. mud got on the gopro early, so quality sucks BUT check out at like the 6:30min mark or so when they hit that back straight. looks to my eye he is hitting upper 30s, low 40 mph on the track. this is our 50cc minerelli modified motor.

[miniquadtuner]

Here is a snipit from an article I wrote on another forum about final drives and CVTs to calculate max speed - just to let you guys know us quad guys do our homework too ;D

in short, if I had a good idea of what max speed is for a scoot in a 1/8 mile run, I'm sure I could settle in final gearing on our side to let our power plant do its best to get us where we need to be.

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CVT ratios explained
I've seen some questions and posts on here before relating final gearing to CVT setup. here is the deal - they are absolutely married to each other. look at the ATV as a system that starts at the crank shaft of the driver all the way to the rear wheel that applies power to the ground. Your system will have one overall initial ratio, and one overall final ratio with the ratio in between handled via the CVT - much like figure 2 but for the whole system, not just the CVT.

example - my motor has a peak RPM of 13k. my CVT is setup to reach over drive, or a final ratio of .75:1. I use the high speed tranny gears and 19/30T final drive. I also use 16" tires. what is my vehicles max theoretical speed?

answer:
-13k at Driver is actually increased (.75:1) such that the driven (rear pulley) is spinning at 17.33k RPMS
-the tranny then reduces by 9:1 such that the counter sprocket is spinning at 1925rpms
-the final gearing is 19/30, so the rear axle is spinning at 1219rpms.
-the 16 inch tires are also spinning at 1219 rpms or move the ATV forward 60,990 inches per minute.
-if you don't feel like doing the math on this one, use this link:http://wahiduddin.net/calc/calc_speed_rpm.htm
-Overall Answer - they ATV's final gearing could reach 58MPH - likely too high for MX setup.
-data used: 13k rpms, Transmission ratio = tranny 9:1 + CVT final .75:1 or 6.75:1. final gearing is 1.578:1 for the 19/30T combo

Why this is important - you can, by accident, design a system that is not practical at all and is wasting HP. the key goal here on overall system ratio - START with picking your top MPH and go backwards from there. for youth MX, 45mph is a good target, maybe less, maybe more you pick. if you add up your system ratio, using the final CVT ratio in the equations above, what is it? you might find the bike is capable or setup to reach 65mph! very nice, but will never use it on the mx track. a lower overall system ratio is needed to use every bit of power to get the bike from 0-45mph as quick as possible. if the rest of your final drive is leaning towards higher speeds like 65mph, and you are trying to bring it down with just the CVT, you have a hard job ahead of you. need to get the final ratios in line so your CVT will not be overworked and inefficient in shifting from 0-45mph on the track with a final drive that is designed for 0-65mph.

[Enviromoto]

Well its hard to say what a 50 will do in a 1/8th as just about everyone is running at least a 70cc. That being said we had a guy from Germany come over last year and run 73mph in the 1/8 @ a little over 7 seconds with a 70cc. Don't get me wrong I have a lot of respect for the miniquad industry and one of my other companies (ZTR Racing Products) contributes parts for that market. However with the power loss of a chain, drive axle, and two extra tires I just don't think its a fair fight. If you guys ever want to come up and do some exhibition throw downs I would be all for it. As far as traveling to GA I don't see that happening for awhile since we stay pretty busy all year in the tri-state area with our race season as well. Great trans tuning writeup and best of luck this year, you guys rock!

www.USAScooterRacing.com