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Hugues
28 March 2012, 0422
Hi guys,

I'm about to order motor and batteries this week and would like to run a last reality check here with whoever has some spare time.

My main pre-occupation is about acceleration. I'm comparing results from 2 spreadsheets (links below) and the figures do not match.

- Total weight incl. driver will be 850 lbs
- Motor is AC-20 running at 96V, but for lack of better specs, I'm taking the 48V specs from here (http://www.electricmotorsport.com/store/pdf-downloads/AC_Drives/AC20.pdf)
- Battery pack is Winston 90ah, 32 cells for about 100V, although this parameter is not taken into account in super_estimator spreadsheet (only torque)

So in my Elmoto 2.18 spreadsheet, here (https://docs.google.com/spreadsheet/ccc?key=0Ag3aJzdmpPwgdFl6TDE3dzhFbWVBRlR5czJqX1BKW VE), i get a 0-60mph acceleration time of about 28 sec, which is quite lousy

In my Super_estimator spreadsheet, here (https://docs.google.com/spreadsheet/ccc?key=0Ag3aJzdmpPwgdHNyUS13QVFEVDdzMVVpcjZEVnBUO Hc), I get 12.6 sec, which is quite reasonable. If i extrapolate a bit the torque curve for 96V, i even get 7 sec , which would be quite great !

All the other data is the same on the spreadsheet, unless i forgot something.

And here comes the reality check : which figure is more plausible ? Anyone as plugged in real life data into these spreadsheets to see if they make sense ?

Below 15 sec, I'm GO to buy my motor and batteries. But above that, i will have to revisit some stuff.

thanks for your time, i'm about to make an important decision here and i don't want to screw up

Hugues
28 March 2012, 0920
I found another online calculator for torque, rpm and speed:
http://vlsicad.ucsd.edu/~sharma/Potpourri/perf_est.html

I plugged in my torque VS rpm data (@48V) and found....12 seconds, very close to the super_estimator spreadsheet,
and needless to say, the value that I prefer to 28 sec from elmoto 2.18 (not to say the spreadsheet is not computing properly, maybe i did not define some parameters correctly)

I'm gonna try to find a third calculator and if it gives a result close to these or below 15 then i order my gear :cool:

2942

Edit: playing with this same calculator, i pushed the "knee" of the torque curve a bit towards 3500 rpm (to simulate 96V) and i get a 0-60mph around 7 cool little seconds !
Is this reality ? Or am i only fooling around with the data until i see something i like ?

Hugues
28 March 2012, 1021
found a third online calculator here,
http://www.theboltonclan.com/asim.html
with 48V torque curve i find...12.5 sec.

cool ! I think I'm go, i don't need anymore evidence, this is gonna be a cool bike !

seanece
28 March 2012, 1047
Good luck with your bike. Sounds like a blast!

Nuts & Volts
28 March 2012, 1214
I created that super_estimator spreadsheet to try to take into account the aerodynamic and rolling resistance forces every 1 mph increments. These forces are subtracted from the torque your motor creates to generate the net force used to acceleration. The largest down fall is that forces is just an average between each mph, this leads to slight inaccuracies. You could do every .5mph step and get closer numbers.

Point being the theory behind the spreadsheet is decently solid, however I haven't been able to test it against real world data.

That last sheet uses a similiar approach to mine and should be quite reliable

Hugues
28 March 2012, 1224
I created that super_estimator spreadsheet to try to take into account the aerodynamic and rolling resistance forces every 1 mph increments. These forces are subtracted from the torque your motor creates to generate the net force used to acceleration. The largest down fall is that forces is just an average between each mph, this leads to slight inaccuracies. You could do every .5mph step and get closer numbers.

Point being the theory behind the spreadsheet is decently solid, however I haven't been able to test it against real world data.

That last sheet uses a similiar approach to mine and should be quite reliable

oh, so you're the one. Great, i could not find the thread anymore where i found it. Thanks.

Surely someone on this forum is running the AC-20 at 48, 72 or 96 V and has timed his 0-60mph, right ?
then we plug-in their gear ratio and weight, and we can have a good estimate,

that would re-assure me somehow, before i press the PAY button. :D

I'll sleep on that...

Allen_okc
28 March 2012, 1224
:cool: as Ed once told me Hugues - when you strap yourself to the chopper, take an extra pair of under ware with you, cause your gonna need them...

Hugues
28 March 2012, 1226
:D

podolefsky
28 March 2012, 1905
I'm running the AC-20 at 72V, 650A controller. 5:1 gearing, 420 lb bike, 150 lb rider. I haven't timed 0-60 perfectly, but I'm sure it's under 7 sec.

I'd be pretty sure that even with an 800 lb bike, at 96V and 6:1 gearing you'd be well under 15 sec.

Skeezmour
28 March 2012, 2019
I'm running the AC-20 at 72V, 650A controller. 5:1 gearing, 420 lb bike, 150 lb rider. I haven't timed 0-60 perfectly, but I'm sure it's under 7 sec.

I'd be pretty sure that even with an 800 lb bike, at 96V and 6:1 gearing you'd be well under 15 sec.

I know with a 1200# sparrow and an AC-35 with that same controller running 115v it did a good job of trying to pull the front wheels off the ground. Even at half power it gets into trafic fine. Full power was almost light the rear tire at will.

Hugues
28 March 2012, 2206
I'm running the AC-20 at 72V, 650A controller. 5:1 gearing, 420 lb bike, 150 lb rider. I haven't timed 0-60 perfectly, but I'm sure it's under 7 sec.

I'd be pretty sure that even with an 800 lb bike, at 96V and 6:1 gearing you'd be well under 15 sec.
allright,
i've plugged in 5:1 and 420+150lb with the 48V torque curve and that gives me 10.6 sec (with 13.3 inch wheel radius), so I guess at 72 V we're pretty much in the area you are saying.

That looks good,

thanks a lot Noha

Hugues
28 March 2012, 2213
I know with a 1200# sparrow and an AC-35 with that same controller running 115v it did a good job of trying to pull the front wheels off the ground. Even at half power it gets into trafic fine. Full power was almost light the rear tire at will.

1'200 lbs :O

Well, i would have to make sacrifice on the battery side to fit an AC-35 in, but at least that leaves me with a plan B,

thanks

Allen_okc
29 March 2012, 0504
:O dang 1200 lbs - thats one heavy machine!!!

podolefsky
29 March 2012, 1601
Just to let you know, I did a *very* rough 0-60 check today. It's around 6-7 sec (that's just me watching the clock on my speedometer while gunning it from a stoplight).

I'm geared exactly 5:1, 72V pack, about 600 lb with bike, rider, and my backpack (I was on the way home from work).

Hugues
29 March 2012, 2117
Just to let you know, I did a *very* rough 0-60 check today. It's around 6-7 sec (that's just me watching the clock on my speedometer while gunning it from a stoplight).

I'm geared exactly 5:1, 72V pack, about 600 lb with bike, rider, and my backpack (I was on the way home from work).
That's great ! Thanks
What's your wheel radius ?
I will then extend the torque curve to fit your time,
Then I will use the curve on my build.

Tony Coiro
29 March 2012, 2158
A friend of mine has a 108V bike, 6.8:1 ratio, AC-20 with Curtis 1238R (650A) and it will do mid 6 second 0-60 times. The bike is 560 pounds since it has 10.5 kWh on board.

Hugues
30 March 2012, 0322
A friend of mine has a 108V bike, 6.8:1 ratio, AC-20 with Curtis 1238R (650A) and it will do mid 6 second 0-60 times. The bike is 560 pounds since it has 10.5 kWh on board.
thanks
super_estimator gives 9.4 sec with 75kgs driver but with 48V torque curve. But i used 13.3 inches wheel radius.
It looks like super_estimator is on the conservative side, or at least not on the optimistic side.

I wish we had the real torque curve at 96V. Well maybe i will be able to produce this data later on this year as i just ordered my motor, controller and batteries yesterday !

thanks for the data guys !

podolefsky
30 March 2012, 0900
Rear wheel radius (at tire edge) is 12.4".

Hugues
30 March 2012, 1105
thanks
i adjusted the torque curve to fit your 6-7 sec time, with your parameters
then put back my parameters with that torque curve and I'm now down at 8.3 sec at 72V from 12.6 sec at 48V
definitely moving in the right direction, seems 96v should be in the 7 sec region, which is cool for my e-cruiser version 1.0.
I'm satisfied with this