So. Myself and a couple buddies are into different kinds of racing. And we've recently taken to drag racing with our racing karts. So naturally being interested electric vehicles and my buddies being nay Sayers towards electric power. I'd like to show them up. Before I plan my build I'd like to have an idea on how much power is required to push say, a 400 pound vehicle with driver to at least 100mph in a 1/4 mile? Any ideas? I'd like to base the power system on some 80mm outrunners I already have for my rc planes so I can stay with some batteries I already have to help with cost. The question is how many I'll need to use?
Electric gokart for drag racing
- Thread starter maeu2003
- Start date
HumboldtRc
100 W
- Joined
- Aug 22, 2010
- Messages
- 267
[youtube]O-MD_4F7sNs[/youtube]
Hillhater
100 TW
Karts have 2 problems in drag racing..
Crap traction due to the tyre size /diameter
Crap Aero drag which kills them after the 1/8 th mile.
and those 80 RC motors wont do it for you ..you need 40-50 kw to make 100mph on the 1/4
Crap traction due to the tyre size /diameter
Crap Aero drag which kills them after the 1/8 th mile.
and those 80 RC motors wont do it for you ..you need 40-50 kw to make 100mph on the 1/4
dogman dan
1 PW
That doesn't matter, he's dragging other karts.
But the motor or motors will have to get bigger. I'm not sure how big. But once you build it, it will slay the gas machines off the line.
It will cost a lot more than the gas machine. Mostly battery costs.
But the motor or motors will have to get bigger. I'm not sure how big. But once you build it, it will slay the gas machines off the line.
It will cost a lot more than the gas machine. Mostly battery costs.
doctorGONZO
100 W
I am an old man who sometimes momentarily lives in the past when I was young and strong and beautiful and wild and crazy. Once upon a time, many years ago today, I rode a 58 Triumph TR6 with aftermarket cams and capped megaphone exhausts and a trick sprocket which was actually OVERDRIVE one tooth. It got on the cam rather abruptly at 2800 RPM and would do 70 MPH at 9,000 RPM in low gear. Usually when I was trying out zero to 60 I would shift from low to second at 50 or 55 because it began to get flat at about 45. It was factory rated at 42 HP (I vaguely remember) and I ran dead even with a box stock 61 Bonneville rated at 46 HP (I vaguely remember)in numerous comparative acceleration science experiments in the quarter.
I ran the quarter too many times to count. My best and worst et's were 14 flat and 15 flat. My best and worst trap speeds were 105 and 95 MPH. Traction was a real problem. The bike bogged unless the RPMs were above the critical 2800. So I had to either spin the tire for 50 feet or slip the clutch. Most of the time I spinned the tire.
The published weight of the wet bike was about 375 pounds. At that time I was a skinny punk teenager that weighed a dam lot less than Arnold Schwartzeneger. Total vehicle weight maybe 500 pounds or a little bit more. More if I was wearing my Harley Motor Davidson black leather jacket.
Total weight ~500 pounds. Total HP ~45 HP. WEIGHT/HP 500/45 = 11.11.
If we assume (only approximately true) that the ratio would hold true for a 400 pound kart (sounds like a HEAVY kart
) then you would need 400/500 x 45 HP = 36 HP to get the same performance of roughly 100 MPH in the quarter.
I figure that the air drag of a kart will be pretty close to same as the air drag of me on my Trump through a quarter. And the traction situation is not really comparable. The prevailing conventional wisdom of drag racers is that weight/HP is what gives the speed through the trap. Losing traction off the line is what determines et elapsed time.
So now, how much is 36 HP in WATTS? I will figure it out after just one more beer OK. :wink: But after another beer I may forget to get back. So best you figure out how much 36 HP is in watts without depending on an unreliable old man.
I ran the quarter too many times to count. My best and worst et's were 14 flat and 15 flat. My best and worst trap speeds were 105 and 95 MPH. Traction was a real problem. The bike bogged unless the RPMs were above the critical 2800. So I had to either spin the tire for 50 feet or slip the clutch. Most of the time I spinned the tire.
The published weight of the wet bike was about 375 pounds. At that time I was a skinny punk teenager that weighed a dam lot less than Arnold Schwartzeneger. Total vehicle weight maybe 500 pounds or a little bit more. More if I was wearing my Harley Motor Davidson black leather jacket.
Total weight ~500 pounds. Total HP ~45 HP. WEIGHT/HP 500/45 = 11.11.
If we assume (only approximately true) that the ratio would hold true for a 400 pound kart (sounds like a HEAVY kart
) then you would need 400/500 x 45 HP = 36 HP to get the same performance of roughly 100 MPH in the quarter.I figure that the air drag of a kart will be pretty close to same as the air drag of me on my Trump through a quarter. And the traction situation is not really comparable. The prevailing conventional wisdom of drag racers is that weight/HP is what gives the speed through the trap. Losing traction off the line is what determines et elapsed time.
So now, how much is 36 HP in WATTS? I will figure it out after just one more beer OK. :wink: But after another beer I may forget to get back. So best you figure out how much 36 HP is in watts without depending on an unreliable old man.
Hillhater
100 TW
36hp = 27,000 watts. ( 27kW )
Off line traction will be a big issue ..as that video above shows.
Bikes have better aero than karts as the bike rider can lay on the tank, whilst the kart driver is sat upright or crouched at best.
doctorGONZO
100 W
Once upon a time back in my glory days many years ago today I always ran the quarter normally upright. When I tried out low gear and did 70 at 9,200 (or was it 72 at 9,000 in all the excitement I lost count myself, maybe was one of each, I did it twice) I was normal upright. The only time I ever tucked in was the time I ran on top, I tucked in neatly, chin on gas tank package rack, but no funny business like Rollie Free on his Vincent. That Lightning was geared to go 90 in low gear My Trump only showed me 118 MPH. Later my best old friend Ray (Really!) splained to me that it was normal to be faster on top in 3rd than 4th like I was.
My guesstimate is that the aero of my quarter runs compares approximately to a kart with a non-tucked driver, so the aero factor might be able to be dropped out of a rough horsepower comparison.
I firmly believe that, if some is good then more is better.
And enough is NOT enough. Too much...now THAT is enough.
So if I was building a kart to do 100 in the quarter, I would plan to use the same 45 HP that my TR6 and Ray;s Bonnie had. If I had the same low-bucks situation as I usually do, then I would see if I was feeling like a lucky punk and try to do it with the extrapolated 36 HP. Back in the day the Tiger 500 was rated at 36 HP and factory claimed to do the ton. It had the same frame and weight as the TR6. Don;t know anything about its quarter performance.
Its fun for me to remember the good ole days. Hope my old man dreams have been helpful.
My Trump only showed me 118 MPH. Later my best old friend Ray (Really!) splained to me that it was normal to be faster on top in 3rd than 4th like I was.My guesstimate is that the aero of my quarter runs compares approximately to a kart with a non-tucked driver, so the aero factor might be able to be dropped out of a rough horsepower comparison.
I firmly believe that, if some is good then more is better.
And enough is NOT enough. Too much...now THAT is enough.
So if I was building a kart to do 100 in the quarter, I would plan to use the same 45 HP that my TR6 and Ray;s Bonnie had. If I had the same low-bucks situation as I usually do, then I would see if I was feeling like a lucky punk and try to do it with the extrapolated 36 HP. Back in the day the Tiger 500 was rated at 36 HP and factory claimed to do the ton. It had the same frame and weight as the TR6. Don;t know anything about its quarter performance.
Its fun for me to remember the good ole days. Hope my old man dreams have been helpful.
Hillhater
100 TW
This is a reality check..
Modified go kart..extended wheelbase, bigger fatter drag tires, 1100cc , 160bhp, GXR bike engine.
sure he will be at 500+ lbs, but even with a huge traction and power advantage...
12.29 sec, 110mph for the 1/4 mile best, and the second pass was only 99 mph
http://www.youtube.com/watch?v=1MAvb6m7JJE
Modified go kart..extended wheelbase, bigger fatter drag tires, 1100cc , 160bhp, GXR bike engine.
sure he will be at 500+ lbs, but even with a huge traction and power advantage...
12.29 sec, 110mph for the 1/4 mile best, and the second pass was only 99 mph
http://www.youtube.com/watch?v=1MAvb6m7JJE
doctorGONZO
100 W
Those numbers are really familiar.
Way back in 1973 I bought a new 73 TransAm. Standard 455HO, automatic,standard axle (355 I think it was). Car magazines in the day reported numbers much like your post for a supertuned but stock car exactly like mine, except trap speed about 105. And the magazines all said the 455HO was stronger than the Street Hemi and they estimated it to have maybe 475 HP. My TA would genuinely Go Like Hell punching it from 110.
Car weight about 3600 p0unds. Weight 3600/Power 475 = 7.6 ET 13.00 Trap Speed 105
Kart ....Weight 550/Power 160 = 3.4 ET 12.3 Trap Speed 110 or 99
Trump TR6 Weight 550/Power 45 = 11.11 ET 14.00 Trap Speed 105
:?
Well, my guess is that the electruic kart aficionado should start with enough little lectric motors to add up to 36 HP and then keep on adding mo motors strapping them on wif duck tape and bailing wire until he gets to his goal of 100 trap speed.
BTW I am not a candidate to drive the kart. Not even with one little lectric motor.
Way back in 1973 I bought a new 73 TransAm. Standard 455HO, automatic,standard axle (355 I think it was). Car magazines in the day reported numbers much like your post for a supertuned but stock car exactly like mine, except trap speed about 105. And the magazines all said the 455HO was stronger than the Street Hemi and they estimated it to have maybe 475 HP. My TA would genuinely Go Like Hell punching it from 110.
Car weight about 3600 p0unds. Weight 3600/Power 475 = 7.6 ET 13.00 Trap Speed 105
Kart ....Weight 550/Power 160 = 3.4 ET 12.3 Trap Speed 110 or 99
Trump TR6 Weight 550/Power 45 = 11.11 ET 14.00 Trap Speed 105
:?
Well, my guess is that the electruic kart aficionado should start with enough little lectric motors to add up to 36 HP and then keep on adding mo motors strapping them on wif duck tape and bailing wire until he gets to his goal of 100 trap speed.
BTW I am not a candidate to drive the kart. Not even with one little lectric motor.
doctorGONZO
100 W
If I correct the numbers for rear wheel HP......
Car 3600 pounds/ 342 HP = 10.8
Trump 550 pounds/ 45 HP = 12.2
This is beginning to make some sense. Now remember that my bike was geared to be in continuous overdrive and bogged under 2800, so my ET could easily have been much better with better drag gearing. I cruised it, not raced it. The TA had ample torque at low RPM so there was no trick to get a good launch. So the ETs could have been much closer.
Trap speeds are by rule of thumb much more closely related to the power to weight ratio than to gearing. So the car and bike trap speeds are a good match to the power to weight ratios.
Now the strange kart numbers for 160 HP. Very strange. The bike before its motor was removed was heavier than the kart and should have had a lower ET and a higher trap speed according to magazine reports. So something really got fouled up either in the kart setup or the driving technique or both.
I do not do youtube on my computer for several important reasons so have no idea what the video shows. But its my opinion that the kart should have performed much better.
There is no reason the kart should not do 100 in the quarter on about 45 HP of electric motors.
Car 3600 pounds/ 342 HP = 10.8
Trump 550 pounds/ 45 HP = 12.2
This is beginning to make some sense. Now remember that my bike was geared to be in continuous overdrive and bogged under 2800, so my ET could easily have been much better with better drag gearing. I cruised it, not raced it. The TA had ample torque at low RPM so there was no trick to get a good launch. So the ETs could have been much closer.
Trap speeds are by rule of thumb much more closely related to the power to weight ratio than to gearing. So the car and bike trap speeds are a good match to the power to weight ratios.
Now the strange kart numbers for 160 HP. Very strange. The bike before its motor was removed was heavier than the kart and should have had a lower ET and a higher trap speed according to magazine reports. So something really got fouled up either in the kart setup or the driving technique or both.
I do not do youtube on my computer for several important reasons so have no idea what the video shows. But its my opinion that the kart should have performed much better.
There is no reason the kart should not do 100 in the quarter on about 45 HP of electric motors.
