Power-to-weight ratio

[sinned]

While reading the write up in the Kiwi Rider magazine on the Street Triple I was drawn by a comment on the power to weight ratio comparison to the Speed Triple.

I have often thought what is the relative power weight ratio comparison of a motorcycle to an mid range powered car and does that relate to the relative feel of acceleration. I have made a few simple calculations. These calcs tell me the Speed Triple is 337% or 3.37X the ability to accelerate as my XR6. However, I can safely give the XR6 full throttle from a standing start but have yet to master applying full throttle in first, second or third gears on the speed triple.

In my calculations I added 80kg to cover a rider plus a bit of fuel. This makes a significant difference to a motorcycle power to weight ratio and practically none to a car. The chart shows the ratio with a rider as no bike accelerates without a rider. It is no wonder a powerful bike brings on a smile and that only a few exotic cars can provide a similar rush.

[The Pastor]

slow day today at work?

[Mikkel]

In my calculations I added 80kg to cover a rider plus a bit of fuel.

For a MALE rider? I'm sorry to say this, but that is the out there with the tooth fairy and other fairytales...

[Pancakes]

For a MALE rider? I'm sorry to say this, but that is the out there with the tooth fairy and other fairytales...

Whatta mean fatty? I'm 73Kg so thats me and 9 - 10L of gas. Even me and the wife is only 120Kg.

Best performance mod for your bike? (Not you Mikkel, just in general) Lose your tubby asses and guts.

[Dave-]

what'd you use for power? horsies or kilowatts?

edit: im 55kg! take that bitches!

[Ocean1]

what'd you use for power? horsies or kilowatts?


Kilowats on the chart.

Get a more real idea of acceleration if you use torque though.

Could bung it in a spreadsheet and sticky it somewhere on site... but there's already far too much marketing mis-information about "power". And in case anyone figures bikes are just naturally quicker try plugging in the numbers for a top fuel rail.

[Dave-]

Kilowats on the chart.

Get a more real idea of acceleration if you use torque though.

Could bung it in a spreadsheet and sticky it somewhere on site... but there's already far too much marketing mis-information about "power". And in case anyone figures bikes are just naturally quicker try plugging in the numbers for a top fuel rail.

nih...duh...helps if i read the chart properly...*mutters* no wonder i was no good at graphs...

bikes have less drag, and a smaller tail

[Sanx]

2007 Honda Fireblade (for sale (http://www.trademe.co.nz/Browse/Listing.aspx?id=128624314), hint hint):

175kg claimed dry weight, so 200ish by the time you account for manufacturers lying, oil, fuel, etc.
Add one fully-leathered me to the equation, and you've 290kg all up.
172 hp at the crank, which equates to a power to weight ratio of: 0.59hp/kg, or 590 hp/tonne.

2007 Bugatti Veyron:

1888kg claimed curb weight, which probably doesn't include fuel, but let's go with this anyway.
Add in a driver with a similar weight to myself, after subtracting a few kilos of cow-skin, and you're at 1973kg. Trophy blonde bimbo, which is probably offered as a factory extra, not included in this total.
1001hp claimed hp, but each production model actually produces between 1020 and 1040hp. Let's go with the highest figure.
This then equates to 0.53hp/kg, or 530 hp/tonne.

And of course, and even better indicator is hp per tonne per dollar (we'll do the calculations as hp/tonne/$1000 in order to avoid very small fractions)...
For the Blade: 30.26, using the standard price of $19,500
For the Veyron: 0.00024, using the standard price of $2,200,000

Hmmm ... I think I win on the bang for buck scale, though Honda don't offer factory-fitted trophy blonde bimbos (just trophy blond homos).

[Ocean1]

Hmmm ... I think I win on the bang for buck scale, though Honda don't offer factory-fitted trophy blonde bimbos (just trophy blond homos).

After market blondes available though, and you get to fit 'em yourself.

Try an Ariel atom in that equation, 650 bhp/ton supercharged. Not sure on price but it should be a fairly competitve BFB.

[fredie]

Whatta mean fatty? I'm 73Kg so thats me and 9 - 10L of gas. Even me and the wife is only 120Kg.

Best performance mod for your bike? (Not you Mikkel, just in general) Lose your tubby asses and guts.

so your wife is like around 40kg:shit:how can she be so tiny:shit:

[Pancakes]

Just keep her on the crack and off the pies eh mate! Shes kinda mid 40's. Little still.

[davereid]

so your wife is like around 40kg:shit:how can she be so tiny:shit:

Fuck, my labrador weighs 40kg... and she is soooo pretty....

Kelly.... here kelly ... come darling "pheep pheep" good girl...

[davereid]

On a more serious note (dog seems to have run away..), some aussie states are looking at power-to weight to determine learner legal bikes, rather than just engine size. http://www.transport.tas.gov.au/__data/assets/pdf_file/0017/15362/Learner_Approved_Motorcycle_Scheme_LAMS.pdf has a list of Tasmania approved learner bikes.

[Sanx]

Some interesting ones on that Tasmanian list. I wouldn't have thought anyone would want to claim the Aprilia SXV550 is learner legal; unless that is you want your learners to wheelie off the throttle in 1st, 2nd and 3rd. Same with some of the big single motards on the list: Husky SM510R, KTM 625SMC, and so on. I do actually think their sums are slightly suspect. The learner legal bikes are to have engines no bigger than 660cc, and a power to weight ratio no greater than 150kW/Ton. Given that thet Aprilia SXV550 has around 70hp and a weight of just 128kg, the power to weight ratio according to my calculations is 406kW/ton. Slightly over the maximum limit, I feel. On the other hand, it's possible they have a similar system to the UK, where if a suitable limiter is installed, it becomes learner legal.
But it's a far more intelligent method of determining learner-suitable bikes than the system here. A DR-Z350 isn't OK - but an RS250 is. Madness.

[Pancakes]

Yeah thats way more sensible. UK is 30 or 33 HP eh. Means different delivery too with IL4's v.s singles or twins coming into play in learners minds.

[WRT]

Given that thet Aprilia SXV550 has around 70hp and a weight of just 128kg, the power to weight ratio according to my calculations is 406kW/ton.

Talking to Strada about the SXV a couple of months ago, apparently they only have 70hp if you derestrict them. Supposed to be not much more than about half that amount from factory, and if you derestrict them the warranty drops to 4 months (this is for road riding, naturally no warranty on competition use).

Stink, eh?

[disenfranchised]

I do actually think their sums are slightly suspect. The learner legal bikes are to have engines no bigger than 660cc, and a power to weight ratio no greater than 150kW/Ton.

Not just suspect either??
I looked up The Indian Scout 741, cause the name suggested it was higher than 660cc. Didn't turn out to be relevant, but at a claimed 30.5 cubic inch capacity that makes it 1.27L, almost double the limit they're supposed to be imposing.

I like the concept, but given that a lot of these might be being sold in "restricted" mode how could they enforce it.
People would be riding round on "approved" bikes, but would have done the required tinkering to release their full power.

Sounds like the potential for trouble.
Surely something like our Moped law would be better
Maximum capacity 250cc
AND Maximum Power < 25kW
AND Maximum Speed < 120km/h

That way there's only limited scope for modifications to get around the rules.