Torque - In the real world

[sudolea]

I wasn't referring to comparing bikes with one another, I was referring to the torque tables I made before for my own "just-for-fun" exercise. Based on these 2 tables from some days ago (the one of my own bike and the one of the K1300S), there is no extra dimension needed. The 2 tables from before showed torque values. So : expressed in Nm.

And to calculate from there the force, delivered at the back wheel (the "thrust", expressed in N), if I didn't make any logical errors, the only extra calculations to be done are :
1. take the torque of the engine at that speed's rpm (in Nm) in that gear,
2. multiply it by all reductions of the concerned gear, and
3. divide it by the (back) wheel's radius (in m). The result's unit dimension is then N.

So e.g. taking the 140Nm, delivered from the K1300S's engine in first gear at it's 100 km/hr's rpm ...
1. the torque is 140 Nm,
2. multiplied by 10.085 (being the primary reduction x secundary reduction x the first gear's reduction),
3. divided by the 0.32 m of the K1300S's back wheel (the value I used)
results in a force of 4406.8 N which is the maximum force the K1300S ever delivers at it's back wheel. Above this speed, the values only decrease.

This must be the number you were after initially, isn't it ?

Indeed, if you want to compare bikes to one another (which wasn't my initial goal), you'd need to add a third dimension. But as from (rough guess) about 100 km/hr, everything will become very unreliable, as the force result will be significantly biased by aerodynamical drag if you ask me... Whereas below that speed, it's difficult to compare. E.g., the K1300S's performance time specs to get from 0 to 100 km/hr say "in under 2.8 seconds". So you'd need quite some precise chronometer 

[black-k1]

You've nicely shown how the "thrust" at the wheel varies by road speed/engine revs within a given gear. Geting the gear right to maximise the ability to do intant overtakes is important.

My original spearsheet came as a result of a converstation with an Old Git owner of an Indian Chief. I'd commented that I was impressed that the flash on my bike had taken the torque up to 111lbft from 104lbft. His response was that I needed to feel "real torque" at 137lbft! I then started to think about why the "real torque" of the Indian didn't appear to equate to significant acceleration on the raod, and that it couldn't just be down to the extra weight of the Indian. What I needed was a number that allowed me to compare what was happening at the wheel-road interface to see what difference there was, and how marked that difference was.

That, in turn, got me thiking about the roll on tests a few of us Old Gits had conducted during a boring ride across the autoroutes of France, and the K1300S riders words to me over the intercom of "Jesus! You just fucked off". Finally, when I had my bike MoT'd the tester was asking about it and the mods I'd had done and asked if I though it was a match for the new Rocket 3. A question I didn't know the answer to.

I think that's my long way around to say that yes, comparison between different bikes, was part of my original requirement, hence throwing in a few extra bikes for comparison.

What I didn't expect to see, but what I'd always suspected, was tht the S1000 engine, in RR tune, but fitted to some form of "RS" frame/bodywork, would make a really good replacement for the K1300S. While it may lack the headline crank torque numbers, the actual riding experience would match or better the space warping abilities of the K1300S, something many on here find really important.

[sudolea]

I can send you that spreadsheet if you'd like to compare any other bike. And even share it with anyone you like, even online, but I just don't feel too much sharing anything publicly on Google (anyone can call me "security-paranoid", but I don't do this). In case you 'd want to compare all these different bikes you mention with bike-specific data, you'd just need the reductions (primary, secundary, gears), the (back) tyre measure, and the torque sheet. So if you want, PM me with your email address, and I'll send it by mail.

[black-k1]

Thanks for the offer of the spreadsheet but, with the exception of the wheel size calculation, it's pretty much what I have already in my spreadsheet. I'd just need to "plug in" the crank torque at different revs values and make that the 2nd dimension per bike rather than the differnet bikes being the second dimension ... if you know what I mean!

[Costas]

The deep and detailed knowledge aquired for K bikes is astonishing.
Still its a bike we love but a bike old, and comparing it only encyclopedic knowledge offers.