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1000 HP dragbike with Ultracapacitors

15337 Views 35 Replies 8 Participants Last post by  Karter2
i want to split out the discussion from the other thread to focus on the technical details of the dragbike project.

Sifting thru their blog pages seems to be the only way to find little bits of info about the details.

Their goal is to do 1/4 mile in 6 seconds at 200 mph, and they call out 1000HP. The electric power supply will come from ultracapacitors, looks like the Ioxus Titan 60 x 108mm axial cells, 2.7/2.85V-2000F, weighing 390 gms each. The drawing indicates 3px210s, so it's ~600V pack (somebody double check my count on that). 630 cells x 390 gms = 540 lbs per dcb.

No word on the motor, but some about the gearbox:
a single speed reduction gearbox, using two sets of 31:59 gears to give an overall ratio of 3.81:1. This reduces the motor's peak speed from 22,000 rpm down to 5,750 rpm, after which a standard motorcycle chain/sprockets set gives us 2.5:1 reduction to the rear-wheel rpm of 2,300.


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also they have stated they want a sub 7 second bike (1/4 mile), comparable to the rocket. The rocket has a 14.kwh pack that makes about 1 megawatt for 7 seconds or thereabouts, and weighs 250 pounds. Basic physics would mandate that replacing the batteries with capacitors (and any necessary converters) and expecting the same performance would require that the energy output at that power level divided by the weight of the energy source (batteries vs caps and converters), needs to be equal.

I recon the caps alone weigh 541 pounds, and 1000hp is %25 less than 1MW. So already the energy source is over twice as heavy and less powerful than the current NEDRA leaders packs, and 28F really sounds like it is gonna come up short, but I haven't dug into the farads required much (seemed pointless given all the other red flags).


edit, I'll see if I can do an ltspice simulation of 28F @600v putting out 1000hp (even though it needs to put out more than 2MW for 7 seconds to be competitive on a density basis)
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ok, got it sorted, 28F @ 600v is *just* enough to make 1000hp for about 7 seconds on paper, but it looks like they are making some terribly naive assumptions about being able to convert a 3 volt source at 300,000 amps at the end of the race (plus extra weight and conversions and that they are 254,000 watts short of the rocket).

edit: so it starts at 600v @ 1250a, and at 6 seconds it is at 3750 amps at 200v, and then it falls off a cliff, surely before the race is over.


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there is also an increased risk of reversing a cap with no margins and over a 3+x voltage drop over a string of 210 caps @ thousands of amps.

edit: apparently that isn't catastrophic, possibly some capacitance loss.
yah kenny threw out the 3600F figure in the other thread, but the simulation (rough approximation) and his research (digging through blogs instead of a scientific or engineering style organization of testing and data by the folks making the claims) have indicated that it is off, but 28F at 600V is still quite a bit short, if you were to take the existing NEDRA leader and replace the battery with 28F ultracaps and a boost converter made of unobtanium.

edit: I don't think it matters if they are 3000F, assuming they are proportionally heavier. ultras have better power density, but it takes energy to do a 7 second 1/4 mile.
more swags on the rocket bike:

if you put in 2000 lbs, and 1340 flywheel hp(battery hp?), you get a 7 second 1/4 mile. So the rocket bike is probably less than 2000 pounds w/rider, that 13 inch GE motor though... So the target is somewhere around the 1MW:2000lbs ratio (sustained for 7 seconds), which doesn't *quite* jibe with the Calculatus in post 2 (746kw @ 2600 lbs = 6 second 1/4 mile). There's a lot of drag at 200mph though, so I dunno how the calculator works.

edit: here is all that page does, I don't see drag factored in, ah well, expect more nasty guesses :)

    /(document.input.hp.value*.854)), (1/3))*5.825;
more comparative data points for drag bikes (roughly speaking):

1030 lbs (rider?)
1000 hp
2 speed
< 5.8 second 1/4 mile @ 245mph
37 pounds of nitromethane per run (mix?)
which is maybe 3.5kwh equivalent, but we know they ICEs aren't real efficient, giant wall of flame from disassociated hydrogen from water in exhaust. (5.765 seconds at 227.10 MPH here

note, I learned there is some funny business too, some (all?) top fuel races are only 1000 feet instead of 1320 feet, so WTF.

<sigh> perhaps not top fuel dragbikes though.
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Also, without following numbers here, don't caps decrease dramatically in voltage as they yield energy?
Yup, I put a constant power graph in post 5., granted races aren't really constant power, but they aren't constant efficiency either, so it is a first order approximation.

I'm sure there's more out there on the byu project.
they changed everything though, i.e. cut the weight in half by removing who know what and the EV1 has no lithium performance figures to compare to. I've been looking at other drag bikes because they should be similar in weight and aerodynamic drag and have some performance numbers to compare to.
ltspice is fun, but you might be over complicating it a bit :) the controller design isn't relevant per-se, indeed changing everything around will invalidate the comparison between caps and batts (excepting for possible power conditioning of the cap output to suit motor/controller requirements).

600V 28F 800HP(596800W) discharge (ideal components)= 300V @ 6.3 seconds, check.


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re: ev1
it sounds like about stock 1/4 mile performance after drastic weight reduction and cutting the range from ~100 miles to 1/4 mile...
At 1/4 Mile: 78.9 mph
At 1 Mile: 80.4 mph

a couple more data points (and variants)

They say it is "electronically limited" to 80mph, but I wonder if it is really BEMF limited, which would give you a KV approximation, i.e. the supercap version was still above ~300v at the end of 1/4 mile.

And 2.5v * 160 = 400v, and 2700F * 160 in series = 17F. So fiddling a bit with the simulation I get an average of 37KW (50HP) discharge, ignoring losses. Given that the byu car only gained 8mph in the last 1/8 mile, it was probably current limited by BEMF.

Note, I don't necessarily agree with the BYU conclusion (especially since it is from the lead age, it would have been closer to 100mph with an even lighter 400v lithium pack), though I imagine the PI probably felt like they had to say something encouraging for their capacitor sponsor or something. Also it looks like they just took an inverter and IGBTs ( for a controller.

edit, looking at that manual, 300VDC bus volts is the lowest undervoltage detection setting for the 460v unit, and they mentioned getting undervoltage warnings at the end of the race, so that is probably how it went down.
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Hi Major, hokey smokes, you've been at this a while! I recall you mentioning using a regular inverter in a car, but didn't put it together.

So what do you think in 2016? a lot of folks are speculating about future capacitor improvements, meanwhile the NEDRA folks cut hundreds of pounds off a lithium pack and get under 7 seconds.

despite the improved cycle life, do you see supercaps competing in drag racing (without some handicapping system)?

edit: here's a breadcrumb trail of Major's ultracap experience ultracap
found an online version with pictures (sorry if it is pirated...)

you can see they hit the knee 3 seconds into the run (or it is a controller artifact) and its down to nearly 300v already, making ~116kw at the capacitor bank. And they are at 1/8 mile at ~ 10 seconds, where distance/time goes nearly linear (speed goes fairly constant) at about 50kw pack power. Finally down to about 22kw at 1/4 mile. ev1 takes maybe 17kw to hold 77 mph, less if you cut out 1000 lbs.

nice to see some actual data.
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That is the big mystery .
Not really, I mean if it looks like a scam and smells like a scam...

There are so many things they have pushed out to the web that are misleading or flat out wrong, and nothing demonstrating ANY scientific rigor, and they hide behind the "kids in STEM" angle.
The capacitors can deliver the power, lipos struggle to provide 2000A
big difference between power and energy, a race of length > 0 requires energy (power * time), and lipos don't appear to be struggling at making power while having much greater energy density. I'm not sure it matters how much >0, but it looks like in this instance the caps would be much heavier for less power and much less energy.

heavy bad.
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