40 mph club

I like to get my calibration check using mile markers. I start though, by setting the speedo to the same as I measure the wheel in metric. For casual use, I'll set speedos to 2020, for a close enough setting for either road or knobby 26" tires.

Calibrated speedo, on a race bike of course.
 
I still say GPS is the easiest most accurate. Mile markers on roads aren't usually placed by surveyors and terrain changes. Lot's of room for error

Measure rollout on wheel to get diameter, set size on cycle analyst, go do a top speed run, doesn't have to be long or far or you max speed, but the higher the speed the more likely you are to calculate the error % correctly.

Compare CA top speed vs GPS top speed. Calculate error percentage, multiply wheel diameter by percentage, double check, done. Takes me an entire 10 mins to get my CA accurate and precise to withing 0.5 mph of GPS. No worries about battery sag, grade changes, making sure you reset and started averaging at the correct point, stopped in time, etc etc.
 
zombiess said:
veloman said:
You guys should be using a bike speedometer, they are more accurate than GPS. Just make sure you measure the tire circumfrence correctly by going one revolution with weight on the tire.
Click to expand...

You are joking right? GPS speed with multiple satellite connections (the more the better) is one of the most accurate ways to read your speed. Tires deform from load while riding changing their circumference, cornering can cause a different diameter because you may be on a shorter radius etc etc etc.

If you want to see really really inaccurate speedometers go ride a sport bike. All the guys that claim to go 170mph+ are sadly disappointed when clocked properly by radar or GPS and often find out they only managed high 150's, timing equipment or GPS. I've seen error rates as high as 15% on motorcycle and car speedos at high speed. I have a video of a friend and I doing 190mph GPS on Garmin in his turbo Porsche 996, speedo read like 203, what a joke, not even close, over 6% error.

Much better to calibrate your bike speedo to GPS if you want it to be accurate.
Click to expand...


I know cars speedometers are off. But a bike speedometer that you calibrated yourself, is very consistent and accurate. I'm not doing high speed runs while corning, so why would that matter? I roll out my tire for circumfrence with my weight on it, so it is deformed correctly. I may be off by a few millimeters, but that's maybe 1 or 2 tenths of a mph at 40mph. The GPS unit I hold in my hand lags horribly. That's enough to throw off your top speed if you only hit it for a second or two.
 
Hit 46mph on the MAC motor running 4kW. The original white gears died 5 days later; coincidence? ;)
Terrifying speed! Now i want to run dual hubs on a dual suspension bike.. run 2.5kW on each motor for 5kW total sustained power..

Do i get my medal for being a power junkie now?
 
Honestly nep, I'm kinda over the 2 hub motor thing. For two reasons:

1) Torque arms for high power setups are a bitch. Especially for a front motor, I imagine. I don't want to have to deal with the headache!

2) I can run 45mph with the ventilated 9c DD and it will only rise over 125c with hills, headwinds, or if I'm off brusing wheelies. And at that power level the battery goes flat reallll quick. Like 15 miles. If I was out in the open running WOT, I don't think I COULD overheat the motor, as crazy as that sounds.

If I was going to build a 2 or 3kwh battery pack, I'd just run an x5. 2 motor setups do sound like a great idea on paper, but KISS ya know? OTOH, running a motor at 125c shows a huge loss in efficiency....

In other news, I've read that automobile speedos are purposely down tuned. Which makes me wonder, if I'm going 45mph on a 35mph road, the people in cars most think they're going 50-55mph. WTH? It's been so long since I've been a driver. does everyone speed?
 
auraslip, you have a point.
Any faster and i need dual suspension. Right now i nearly get knocked off my bike when i hit a bump.
Front motors on suspension forks = bad news..

But crystalyte 5xxxx = stupid heavy :(

You win.. for now!
 
I dunnu if I win... just saying it's a lot of headache for little gain.... for me it's not really about performance... front hub would probably just spin unless it was current limited on starts, but then you lose the perks of acceleration and mid band power. If you could make a circuit that limits current from the PWM of motor speed it'd be great though. I'd really want it for the efficiency reasons. Less heat, more cooling area, etc etc.

Do you really have trouble with bumps on a hard tail? Maybe my roads are exceptionally smooth, or it's just that I run in the open country most of the time but I don't find it a burden. Also got 2.5" tires and a suspension seat post. Not sure if I like the seat post yet.
I have been tearing it up in the fields and berms on the side of the road though. It's pretty awesome to fly through them at 25mph and ramp over the drainage rise from the driveways. I see the appeal of a FS frame, but it's not that bad for occasional off road use. I must say I've never used a bad suspension fork. I started with the bomber, which is low level stuff, but perhaps it makes the ride a lot better.

Another thing to think about is that 2 9c motors weigh as much as one x5, and with the 15 lbs of weight in the front wheelies are harder :D

OTOH, finding 20" or 24" wheels in disc rims is impossible, so having cell-man send you a set of wheels for a daulie would pay for itself if you wanted to run 20" or 24" tires.
 
I was thinking that i'd actually engage the rear motor first, then engage the front to reduce the shock loading on the front suspension fork..

I do have significant problems on bumps, mainly with my front end flying about when i hit a pothole.
Part of it probably has to do with the fact that i don't tuck in so much, and ride mainly upright, so the weight isn't distributed well for sure. I find it more difficult to pedal when crouched down though :|

dual 20in. wheels would be badass.. that's for another bike though :)
 
neptronix said:
Do i get my medal for being a power junkie now?
Click to expand...
Since the medals are cast from the melted windings of your first totally fried motor, then maybe. :) Got one yet?
 
You mean my surly solid front fork isn't good enough? :mrgreen:
Actually when i had front suspension, i had the same issue, mainly on the uphill.

Maybe i need to build a bobber.


Amberwolf: ooh, haven't gotten there yet, the gears on my hub go long before the copper. Perhaps i can melt down my peanut butter gears for the cause.. ^_^
 
I suppose it would at least have the advantage of being easier to cast. ;)

Having said what I did earlier, I recalled that I still have my old 250W Unite scooter motor that I pretty well totally destroyed in my early ebike quest. :lol: It's partially unwound, in a box with the rest of the unwound wire on a spool (I had had hopes of rewinding all the good wire back on once I got the toasted parts of the winding off, until I learned better).

I am wondering if I could actually build a little kiln to melt the copper down and cast myself such a medal. :lol:
 
auraslip said:
Ain't nothing like jumping off a side walk going 30mph. Peoples mouths be like :shock:
Click to expand...


I could use this ability fairly often. Would also need rear suspension though, I feel. I've done it on my road bike, going 35. Any slower and it hits too hard on the landing. Why did I go on a side at 35 on my road bike? Downhill with a group and a car got in the way.
 
On car speedos I know at least the 1997-2004 Corvette and 1998-2002 Camaro/TransAm speedos are accurate at all speeds since I've had experience with probably 200ish of them for tuning. Their speedometers are electronically calibrated based on revolutions of tire per mile, pulses off the transmission drive shaft output and gear ratio. The reason they have so many to adjust is different ones are used for different functions such as transmission shift pressures/etc.

For us fast ebike guys something else to think about is tire growth at speed. If you don't believe me to spin your 26" wheel up to 40-50mph and you can visibly see the tire grow a tiny bit. My old 26x10.5R15 cheater slicks would grow about 1.25 inches at 135mph.

What does all this have to do with the 40mph club... just me repeating, use a freaking GPS, it's more accurate :p :lol:
 
Just dropping in to say that my Stealth bomber hits over 40mph out of the crate, the best i have seen so far is 48.1mph, plenty fast enough for me!!
I have changed the Duro's for Moto rt's at 50psi though, they roll much faster, oh and corrected the rolling distance per revolution of the wheel in the CA.
At the other extreme on a steady ride out with the wife on here ebike averaging 17mph ish the bomber has done over 67 miles on a single charge.
 
I find most car speedo's spot on, when you have the tire size on the door on those rims. Nowdays everybody is running something else on some fancy wheels. My subaru is spot on for speed and mileage.

For sure, you can't use just any mile marker. To get really good calibration, you have to go several miles and use mile markers you have confirmed somehow. They definitely get shifted a few feet when exits or driveways interfere. Ideally, a flat piece of road, and you could confirm the mile markers positions with something fairly accurate, like google earth, or a topo map.
 
dogman said:
I find most car speedo's spot on, when you have the tire size on the door on those rims. Nowdays everybody is running something else on some fancy wheels. My subaru is spot on for speed and mileage.

For sure, you can't use just any mile marker. To get really good calibration, you have to go several miles and use mile markers you have confirmed somehow. They definitely get shifted a few feet when exits or driveways interfere. Ideally, a flat piece of road, and you could confirm the mile markers positions with something fairly accurate, like google earth, or a topo map.
Click to expand...

Or just use GPS :mrgreen:
 
im just short of the 40mph club.

got back from a ride today, and maximum speed was 63.7kmh (39.58mph).
not exactly sure where that speed was recorded. was going fast a lot today.

have to keep trying i guess. :twisted:

Jason.
 
New entry here. 41mph sustained for over a 1/4 mile while riding with traffic down a fast 4 lane road with no shoulder or bike lane, so I took the lane and let the 6 turn go like it wants to. The 20mph tailwind didn't hurt either.

So perhaps not the most legitimate 40mph, but I could easily do 40mph in fair conditions if I just upped my amps. No load speed on 48v 6 turn Mac in 26" wheel is high 40mph range.
 
I get 6x kph mostly, when the wind is calm and the road is fine i get easily 7x kph even at steep hills so yeah... I'm in the 40mph club.
 
40MPH Club! :mrgreen: I made did quite a long time ago but since I got high speed record today I thought I'll update!
I got 48.2mph going slight down hill while wind was pushing me forward! I did have 83.4v hot lipo, the thing is...I wasnt doind speed testing and instead I was just going to Sport centre lol
 
Today I spent quite a while at 45mph while on the frontage road. 72v on a 2808-ish wind of the yescomusa hub. 120% throttle setting gets it done when needed. Though there is no modulation, it's 100% power or off. 100% throttle gets about 40mph tops. Once I get my other build done I might go for the 50mph club, but this death wobble machine I'm currently on with it's severely worn out suspension pivot bushings can get very sketchy.

Battery was 51v a123 9ah 26650 pack and 7s 10ah headway. Limited to 26amps. I never need that much power though.
 
If it's that wobbly, I hope you got some leathers. The race bike I built for 50 mph was a rock solid steel hardtail. You MUST have a good frame above 30 mph. Harder to do with suspension bikes, since there is going to be some play in the pivots.
 
I'd forgotten about this thread! In truth I broke 40 on flat ground with my Kona Stinky a few years ago, but it couldn't hit 40 every ride.
Now I have the Killer Tomato, and its breaking 40 even with the shake-down limits of 3/4 voltage and 1/2 wattage.

Speed.jpg
 
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