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Old 04-16-2007, 04:08 PM   #1
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Default Help rollout!

Gday,

I raced electric onroad at a new track for the first time the other day, and the track recommends a rollout of about 50mm.

My rollout was about 25-30mm, 85 spur with 28 pinion, so I had lots of punch but lost them on the straights.

Borrowed a 35t pinion of a bloke, came second in the B final (which I'm very proud of) but the motor was hot and nearly smoking.

I checked the rollout of the new pinion combination when I got home, and its only around 35mm.

What am I doing wrong?

What am I missing?

I also found out that its pretty well impossible to get a 50mm rollout on the car.

Any help muchly appreciated

It's a HPI Sprint 2.
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Old 04-16-2007, 04:21 PM   #2
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You can mess around with the rollout and gear ratio's in R/C Gear. Heres the link http://sourceforge.net/projects/rc-gear/ Download it and then you can run it without installing it.
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Old 04-16-2007, 04:27 PM   #3
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50mm of rollout is masively huge even for 540.

As for the motor getting hot next time find someone with a temp gun and you wouldn't it to be more than 60C or 140F on the can.

If it's still getting to hot get a 30 x 30mm fan to blow on the endbell either a muchmore or novak are good.

Aslo if the drivetrain or even the gearmesh is tight it will be putting extra load on the motor get hotter.
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Old 04-16-2007, 04:47 PM   #4
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Ashley,

Keep in mind that a motor can get hot if its undergeared just as easily as if its overgeared. The best thing to do is to get help from a local racer at your track that is willing to help. Most people in this sport are willing. Do you know the equation to help determine your rollout?

Steve
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Old 04-16-2007, 05:22 PM   #5
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You can go to gearchart.com and down load all the ratios and rollout charts you want, just fill in the blanks.
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Old 04-16-2007, 05:25 PM   #6
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I had printed out charts from the gearcharts website, and I had a play with them, but no matter what combo I use I can't get the right rollout!

According to the rollout chart - the rollout currently is 26.75mm - thats with 85spur/28 pinion and 63mm diameter tyres...

with the 35t pinion I was using when the motor got toasty, gearchart says the rollout is 33.42mm

No where near the ideal rollout!
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Old 04-16-2007, 05:33 PM   #7
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Could i be being too hard on the throttle?
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Old 04-16-2007, 05:53 PM   #8
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Are you and you friend using the same motors, batteries, etc? I tried to match the rollout of some guys I race with (stock, rubber tire) and decided that I didn't like my motors coming off the track at 200 F+, I had different motors than they did, and had to use a different rollout, I was running a HPI Pro3 at the time.
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Old 04-16-2007, 06:01 PM   #9
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I was using a 540 tamiya sport tuned motor - most of the other blokes are using johnson 540 silver can motors - I know the sport tuned revs harder, but I wonder if the silver can has more tourqe?

Some more background - using a futaba speedy, and intellect 4200 stick packs

thanks for all your help guys
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Old 04-17-2007, 12:41 AM   #10
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If your racing with the sprint 2 mate, get rid of it. It's a peice of rubbish (I had one and gearing was my biggest problem) plus you have to deal with the motor touching the belt if you gear up to high. The ratio on gear chart is wrong to btw it lists the cyclone internal gear ratio 2.4375. The sprint 2 ratio is 2.13. I was using a 72t spur and 37t pinion in mine and I got some good performance without burning the motor.

Hope that helps.

Cheers
Adrian

PS Buy yourself a top of the line car mate even if its only 540 it makes all the difference.
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Old 04-17-2007, 01:42 AM   #11
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thanks again for all the help you guys have given me - thats what i love about this forum...

my biggest problem was it was my first race at a new club and they have different classes - I would have normally raced the Sprint 2 in RTR at england park, but when I went to meakin park there was a 540 class - which I thought was the same thing...

Got a rude shock when I found out the other cars were mostly $1000 cars with $20 motors...

lol

I'll keep drifting the HPI until I break it then buy something better!

Cheers guys
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Old 04-20-2007, 02:49 PM   #12
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Quote:
Originally Posted by corallyman
Ashley,

Keep in mind that a motor can get hot if its undergeared just as easily as if its overgeared. The best thing to do is to get help from a local racer at your track that is willing to help. Most people in this sport are willing. Do you know the equation to help determine your rollout?

Steve
I finally figured out what you were saying in your post!

Should a 540 motor burn up with a 50mm rollout?

cheers
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Old 04-20-2007, 02:59 PM   #13
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I use http://www.gearchart.com/
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Old 04-20-2007, 03:42 PM   #14
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Ashley, not even most of the drivers at Meakin run in 540 with $1000 chassis. There are a few who do it just for fun, but dont be put off by that. If you are making it to the "A" Final you are doing well. My dad runs there with a RTR TC4. He does ok as well.

Not sure where you got a 50 rollout for Meakin, that would be the higher extream. When I ran 540 there I had a rollout of 45 - 46 with my old RDX.

Do you know what the transmision ratio is for your car? Has it changed from original?
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Old 04-20-2007, 06:00 PM   #15
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It's 2.13, not 2.435 as listed in gearchart.com

Cheers
Adrian
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