530 gearing ?

[blowerbike]

1150 ratio is different by 2 teeth.
the 1150 has 89 teeth on the basket.
the 1100 has 87 teeth.
ideal situation is crossing the stripes at max hp/rpm whether is be in 4th or 5th gear.
on a drag bike then you would want max hp/rpm in 5th when crossing the stripes.
it is quite simple but quite difficult to figure what you need unless you spend every free minute at the drags testing.
i used to go 3-4 times a week depending on the track schedules and if they overlapped with each other.
i am lucky enough to have 3 tracks all within an hour of me.

[posplayr]

This is an interesting statement.

Yes, in road racing, you want the bike right at or under redline at the end of the longest straight in top gear. You don't want to be bouncing off the limiter as bikes are going by you, and you don't want to be geared unnecessarily high for starts. Assuming that doesn't totally wreck your gearing choice for some other corner.

But drag racing? I would assume you'd want as low of gearing as you could get away with because the launch is so important. On the other hand, if you're wheelieing hard, or shifting too early, I can see how this could slow you down.

I have a 530 setup with a 17 tooth front and a 48 or 45 rear. I ran the 48 with my 1100 motor and did a 11.5 at 118. But I have no idea what my RPM was across the line. I have the 17/48 still on the bike. I also have a 190/70-17 rear.

I thought the 1100 and 1150 transmissions are the same ratios. True?
Am I going to hit the redline before I cross the line?

I guess I can take the 45 tooth rear and some wrenches with me.

-Kevin

I chose to state the obvious rather than try over simplified analysis of a complex problem. People with first hand knowledge would have better handle on that. Whoever I could probably figure it out with some test data and a little model


Here is a little puzzle. If you have an electric car and one gear and no drag, what defines the optimum gear ratio to fastest ET? Keep it simple a constant max torque motor output.

[CivilRock]

1150 ratio is different by 2 teeth.
the 1150 has 89 teeth on the basket.
the 1100 has 87 teeth.

So the 1150 is geared lower? - hope I'm saying that right. As in the 1150 will be turning slightly more RPM than the 1100 given everything else is the same?

Here's my supermoto experience: KTM SMR450. Geared to go about 98mph for Euro Supermotard Racing. Our tracks here never got to more than 60-70 mph. I never used 6th gear in a race, and I would have to slip 1st gear sooooo long at the starts.

I finally geared way down and added a "holeshot" device. (It's a little button/clip that holds the front down until the first bump) I went from starting mid pack to starting in the top 3. I still hardly ever used 6th gear, but the lower first gear helped a ton on the starts.

IDK if that lesson translates to a bike that weighs 2x as much with 1/3 the suspension. Maybe it's me.

I'm trying to get a hall pass to go to the strip tonight and see if 4 months of work on my bike will net me lower times. I'd hate to get there and have to turn up my rev limiter just to make it across the line.

BTW, what is a safe limit on a stock 1150? I have it set at 9500, which I thought was the tach redline (which I don't have), but my builder buddy said 11,000.

Thanks,
Kevin

[CivilRock]

Here is a little puzzle. If you have an electric car and one gear and no drag, what defines the optimum gear ratio to fastest ET? Keep it simple a constant max torque motor output.

1:1 with the motor attached directly to the wheel. I think the gearing would be the only losses in power.

I love this question.

But if the motor had a speed limit, wouldn't you want to want to gear it down as far as you could until you were at the motor's limit at the finish line?

Finish line wheel RPM = 2500
Electric motor max RPM = 10,000
Then gear ratio should be 4:1

That's my answer. You want to most leverage possible without blowing up the motor.

-kevin

[blowerbike]

10500 is safe RPM for the rev limiter on a stock engine.
and yes your saying it right....the 1150 engine is geared lower.

[posplayr]

1:1 with the motor attached directly to the wheel. I think the gearing would be the only losses in power.

I love this question.

But if the motor had a speed limit, wouldn't you want to want to gear it down as far as you could until you were at the motor's limit at the finish line?

Finish line wheel RPM = 2500
Electric motor max RPM = 10,000
Then gear ratio should be 4:1

That's my answer. You want to most leverage possible without blowing up the motor.

-kevin

Ignoring the maximum RPM issues, the answer is the elapsed time is minimized when the cars weight reflected through the gear box is the same as the rotational inertia of the motor.

It is pretty easy to show that a minimum time optimization is achieved when the two inertias are matched. And yes I am sure, I based a multi million $ design optimization based on the principle.

What that means is that 1:1 is only optimum if the inertia of turning the engine is equivalent of moving the car. If the car is 4 times the mass, then the GR is 2.

Now what does that have to do with a gasoline powered drag bike? I don't know

[tom]

well i went to the catskills with skip hikermike and more but i ran on the highway with 18/50 not to bad but it pull good for the street highway not bad but might go with 18/48 but like it with the 18/50 stayed with the bandit 1200 all good we did not line up just having fun

[hotrods316]

tom, i run 18/40 on my lsr bike. 1-2-3 both pretty good shifts, 3-4 was a long gear so i shorted it before the speedtrap.

got a 50 from nessism to play with at the drags.

[jimb12]

I am using my 750 on street and track (road course) can someone help me on changing the gearing for the 530 pitch vx the 630. need around 140 mph at red line top gear. what do you think???? Can the sprocket from Z1 18 front work on the 78' GS 750's

Is that 140mph from a timing trap or the speedometer? That will make a big difference on what gearing you'd choose, since the speedometer is full of crap.

[Rob S.]

Actually the goal is to get to the finish line in the shortest time.

The definition of a drag race - lowest ET for the quarter mile.

[CivilRock]

I was out on a ride yesterday and realized there's a much easier way to figure this out. I noted that in top gear at 60 mph I was at almost exactly 4,000 RPM.

So if my redline is 10,500 RPM, then my theoretical* top speed is 157 MPH.
Oh, and I'm 17/47 (not 48).**

I want to be in the high 10 second range and I'm guessing 125mph. End of story: I don't think I'll run out of gearing. If anything, I should think about going to a 49 or 50 rear sprocket.***

-Kevin

* - I don't know if my bike has enough power to get there.
*2 - I remember reading about MotoGP bikes in 2005 or so having a wheel speed difference of about 30 mph on the straights. So in order to go 200 mph their theoretical gearing has to be in the 230 mph range.
** - 1150 motor, 530 chain, 17t front, 47t rear, 190/70-17 Dunlop rear tire.
*** - I would do this today, but my axle is adjusted all the way forward. I'd have to buy a new longer chain. (or extend the one I have)

[posplayr]

I was out on a ride yesterday and realized there's a much easier way to figure this out. I noted that in top gear at 60 mph I was at almost exactly 4,000 RPM.

So if my redline is 10,500 RPM, then my theoretical* top speed is 157 MPH.
Oh, and I'm 17/47 (not 48).**

I want to be in the high 10 second range and I'm guessing 125mph. End of story: I don't think I'll run out of gearing. If anything, I should think about going to a 49 or 50 rear sprocket.***

-Kevin

* - I don't know if my bike has enough power to get there.
*2 - I remember reading about MotoGP bikes in 2005 or so having a wheel speed difference of about 30 mph on the straights. So in order to go 200 mph their theoretical gearing has to be in the 230 mph range.
** - 1150 motor, 530 chain, 17t front, 47t rear, 190/70-17 Dunlop rear tire.
*** - I would do this today, but my axle is adjusted all the way forward. I'd have to buy a new longer chain. (or extend the one I have)

Not sure what you think you figured out? But yes most stock gearing is set for a comfortable and economical cruising speed/RPM combination which is a typically a lower GR than one that can achieve lower ET's or higher acceleration. So to a limit increasing your GR will give you better acceleration.

For drag racing: At some point there is a maximum acceleration (in lower gears) that you can achieve due primarily to limits in "tractive effort". One you have maximized tractive effort do you still have the right gearing for the traps (top gear)? This assumes you know how to optimize shift points in between. "Tractive effort" is how much force can be transmitted to the ground through the tire/track surface. This has to do with friction coefficents, slip speeds, weight transfer .

For MotoGP tractive effort is not some much an issue, it is torque production in the speed range you are looking at. Higher torque always produces faster acceleration all things being equal.

[CivilRock]

Not sure what you think you figured out?

That I'm not going to hit the rev limiter before I cross the finish. For some reason I thought I was close to redline last time... But now that I replay it in my head, I think I barely got into 5th before the finish. That's right... Hum. Now that I think about it, I was almost able to finish in 4th.

For drag racing: At some point there is a maximum acceleration (in lower gears) that you can achieve due primarily to limits in "tractive effort".

Maybe with a wheelie bar or extended swingarm? But in my case, traction is not an issue. Fighting a wheelie off the line is. That's a 190 road race rear at 20 psi. I was amazed how sticky the track is behind the line. It's like putting your boots down on fly paper.

I had a co-worker that built drag cars in his spare time. He explained to me that the top fuel dragsters accelerated hardest at the end of the strip when the downforce was the greatest. That they are spinning the tires the whole way. They have more power than they can transfer to the ground. I was amazed with that concept. They basically can't apply full power off the start.

I think what I need is a 50t rear and a longer chain both to accommodate the larger sprocket and to move my axle further back in its adjustment range.

Posplayer- you really make me think. Thanks.

-Kevin

[mrbill5491]

The definition of a drag race - lowest ET for the quarter mile.

Fastest Reaction time-->lowest ET=WIN speed is in there somewhere lol.

[stetracer]

I had a co-worker that built drag cars in his spare time. He explained to me that the top fuel dragsters accelerated hardest at the end of the strip when the downforce was the greatest.

" no they can apply the most amount of power to the ground at the end of the track but the hardest acceleration is at the start."

That they are spinning the tires the whole way.

"No they are on the edge of traction loss but not spinning the tires."

They have more power than they can transfer to the ground.

''Yes they do. It is clutch management all the way to keep the tires from spinning.''

I was amazed with that concept. They basically can't apply full power off the start.

" Your buddy is some what right But they can't apply full power to the track anywhere on the track. They produce more power than they can ever use."

I think what I need is a 50t rear and a longer chain both to accommodate the larger sprocket and to move my axle further back in its adjustment range.

You could use a 16t countershaft sprocket and your chain will work fine.

-Kevin

Another interesting fact about top fuel dragsters is they pull more G's when the Shute is opened than they do on the launch