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View Full Version : Rorty Car at the dunes Video!



dune
04-09-2007, 08:03 AM
http://www.youtube.com/watch?v=6qblv7H9Z2s

rowycoracing
04-09-2007, 12:28 PM
Nice!

Rorty
04-09-2007, 03:31 PM
Excellent stuff! Did the young lad enjoy himself?

I see now why the clutch burnt out; the gearing is way too high and your dipping the clutch to gain some punch just exacerbated the problem. With lower gearing, you'll move much quicker, she'll pull like a mule with its ears back and you won't feel the need to dip the clutch.

It's so nearly there, which when you think about it, isn't at all bad for a second time driven car! Well done! *[smilie=bow.gif] I'm jealous!

bikelomen
04-09-2007, 04:29 PM
Looks great Dune. Cant wait to get mine running. Motor is getting shiped Tuesday so We will see When I can get some time in the seat

dune
04-09-2007, 05:50 PM
Rorty, Your correct as usual... [smilie=bow.gif] I mentioned earlier that I had to feather/dip the clutch to get punch out of the turns even in second gear. The sand tires and the sand really load up the drive system. So lower gearing and a stronger clutch is what I'm after. The ride though felt really good. The suspension was really taking it nicely. Haven't had a chance to yank the motor yet so I'm hoping it's only the clutch that has failed... When I shift into gear I can feel/ hear the drive gear set the chain so I believe the tranny is fine just no go when the clutch is released.

Both of my boys thought it was great! We had a lot of fun...

Bike hoping you the best with the new motor/setup. Hope your going to try it out *stock before you pump a bunch more $$$ into it. Can't wait to see it running!


The Rorty car got allot of attention at the dunes. Many people were interested in it (what's this?, what's that? [smilie=biggrin.gif] )

I also posted The vid and some photos on my build thread

Rorty
04-09-2007, 06:23 PM
...So lower gearing and a stronger clutch is what I'm after.

I'm tipping it is just the clutch plates that have suffered. With the right gearing, the standard plates (or even better, a set of Barnett plates) will hold up just fine. These machines don't like the clutch to be slipped (like when engaging the clutch in a car); the clutch in these buggies is more like an on/off switch. When the gearing is right, it's just a case of putting the car into gear and letting the clutch off instantly while applying the throttle and it won't stall. The bikes are obviously dissimilar because of the weight difference.

K-fab may pop his head up now and mention something about CVT or what ever it's called! http://i20.photobucket.com/albums/b237/Rorty/PIX/Smilies/tongue_out.gif

dune
04-09-2007, 06:29 PM
Gotcha!, I'm looking at Barnett setup as we speak.

Gene
04-09-2007, 07:35 PM
Congrats on another great run! The R16 is so different from most minis that it must have been a big attention getter at the dunes. It looked as though it was riding really well and seeing the front wheels come up a few times looked fun.

Any loose nuts besides your crew?

bikelomen
04-09-2007, 08:11 PM
Dune,
I have sprockets for the rear gear box from 15 to 18 teeth and I am now thinking seeing your car that I might want to start with the 18 on the back to give it a bit of umph. I would rather have a really low first then a tall one. Do you know what your running in the front and the back? My gear box is set to 5-1. I do not know the math to figure on if I have a 15 on front and an 18 on back ( I am not sure of what the stock front sprocket is on the gsxr 1000 yet.)

dune
04-09-2007, 08:45 PM
Bike, I'm currently running 16/16. 16 is the stock gear for the front on the CBR. I'm getting a 17 and 18 from danno for the input shaft on the FNR. The 18 should stand it on it's tail if wanted. I may also try a 15 up front at some point. Just ordered the barnett clutch kit as well. In the sand the 18 is my guess on the desert you may be ok with the 17.

My box is a 4.6:1 This is what I was told to get. How did you determine the 5:1?

I did pull the clutch cover and found some ugly broken and smeared plates got it all cleaned out and ready for new ones. *

Someone chime in and explain the box ratios for me....I'm stupid [smilie=biggrin.gif]

bikelomen
04-09-2007, 08:48 PM
Dan told me the ratio when he sold it to me.

rowycoracing
04-09-2007, 09:03 PM
Bike, I'm currently running 16/16. 16 is the stock gear for the front on the CBR. I'm getting a 17 and 18 from danno for the input shaft on the FNR. The 18 should stand it on it's tail if wanted. I may also try a 15 up front at some point. Just ordered the barnett clutch kit as well. In the sand the 18 is my guess on the desert you may be ok with the 17.

My box is a 4.6:1 This is what I was told to get. How did you determine the 5:1?

I did pull the clutch cover and found some ugly broken and smeared plates got it all cleaned out and ready for new ones. *

Someone chime in and explain the box ratios for me....I'm stupid [smilie=biggrin.gif]

With the current set up of 16 tooth to 16 tooth, then through a 4.6:1 box you get a drive ratio of 4.6:1 (obviously) for the drive system after the engine (ie not including the engine primary and gear ratios). *If instead you change it so that you have a 16 tooth to an 18 tooth and then through the 4.6:1 box then your post engine drive ratio is 5.175:1. *If you drop the front sprocket to 15 teeth and keep the 18 on the input of the box then you will have 5.52:1 ratio. *Of course tire size (diameter) is another big lever. How tall are your tires and what is the desired red line of your engine? *I have the primary ratio and gear ratio's for the CBR 1000rr in my CBR manual so if you give me desired RPM and tire size I can run a speed versus RPM curve for you to illustrate.

Rorty
04-09-2007, 09:10 PM
Bike engine/transmissions differ from car engines/transmissions in as much as bike's have a primary drive ratio (crank to clutch/input shaft). It's normally gear or chain driven (ratios vary), whereas a car's engine feeds into the transmission 1:1.

So, to establish the final drive ratio with a bike engine/transmission with FNR, you need to multiply the bike's primary ratio by the gear ratio (1st, 2nd etc.) and then multiply that by the chain drive ratio (the bike's sprocket X the FNR sprocket), which in Dune's case is 1:1 (16/16). That lot then needs to be multiplied by the FNR's internal ratio (Dan makes several different ratios for different uses). Now you have the final drive ratio which can be used (along with engine RPM and tyre circumference) to determine the speed in any given gear and ultimately, top speed (theoretical). You can also use the same figures to calculate any need changes to the chain drive for different tyre sizes etc.

Your bike's workshop manual will give you the primary and gear ratios. It's worth keeping an Excel file for your specific set-ups including the basic gearing and variations of the chain drive and tyre diameters. That way, should you forget (I can't remember from one end of the day to the next!), you can quickly look up what particular combination worked well for you the last time you went to X track, or Y dunes etc.

dune
04-09-2007, 09:26 PM
Thanks guys, All makes good sense to me.

flyerrider
04-09-2007, 09:52 PM
Sweet Vid!!! *Nice music choice too. *It didn't read your other thread but did the clutch end your weekend early?

rowycoracing
04-09-2007, 09:55 PM
Here is an illustration for you. *If I just assume 30" tall tires and use '04 - '05 CBR 1000rr primary and gear box ratios three different set ups calculate out like this...

With the set up as is now 16 tooth --> 16 tooth then through the 4.6:1 box:
Speed in first gear at 2000 rpm = 9.5 mph
Speed in first gear at 8000 rpm = 38 mph
speed in second gear at 2000 rpm = 12.5 mph
speed in second gear at 8000 rpm = 50 mph
speed at 13,000 rpm in 6th gear = 135.5 mph

Change your set up to 16 tooth --> 18 tooth, 4.6:1 box then you get:
Speed in first gear at 2000 rpm = 8.5 mph
Speed in first gear at 8000 rpm = 34 mph
speed in second gear at 2000 rpm = 11 mph
speed in second gear at 8000 rpm = 44 mph
speed at 13,000 rpm in 6th gear = 120 mph

Change to 15 --> 18 with the 4.6:1 and you get:
Speed in first gear at 2000 rpm = 8 mph
Speed in first gear at 8000 rpm = 31 mph
speed in second gear at 2000 rpm = 10 mph
speed in second gear at 8000 rpm = 41 mph
speed at 13,000 rpm in 6th gear = 113 mph

Of course I have no idea what size tires were on there so this is just an illustration of the impact that changing the sprockets a few teeth up or down will have. *Tim

dune
04-09-2007, 11:31 PM
Sweet Vid!!! *Nice music choice too. *It didn't read your other thread but did the clutch end your weekend early?


Yeah, the clutch went out on the second day. So that was it for the buggy testing. Still had lots to do with the kids on the Quads for the rest of the weekend.

dune
04-09-2007, 11:35 PM
Tim, Wow! Thanks for the chart. I think your close with your calcs. The rear sands gotta be 30".

K-fab
04-10-2007, 06:56 AM
If you find that the gearing is too tall even with the 15/18 setup, you can always change the ratio inside the RPM box. *It's not hard to do at all.

Rorty
04-10-2007, 07:53 AM
Tim's last gearing illustration is 5.52:1 which is OK, but I think you would find 6:1 just about perfect (aren't your AT tyres 30" tall too?). It might be worth talking to Dan about lower ratio gears for the FNR.