Building a race bike

Two great lessons, always good to have one of those engineer type blokes about and cash is king. I learned a while back maths is never simple so I leave it to the engineer blokes. And even then they still balls it up, my favourite was being told a certain sized structural member was needed and me having to explain it wouldn't fit in the space available where the roofline and thickness met the wall, he never did get it.
 
There are engineers who are academics and have never laid hands on tools, and there are those who have done some hands-on work.  I'm thankful that I'm the second type. I came from a trade background before I did an engineering degree.

I've worked with the academic type and sometimes it's hard to explain real world issues to them. I once had a boss who was like that. He was a clever bloke who had two degrees - a PhD in physics from a University in India, plus an electrical engineering degree from a university in USA. He'd actually worked for NASA for a short time when he was in USA. He could speak several languages and had written a bunch of academic papers. But I don't think he'd ever so much as picked up a screwdriver. He'd design stuff that was physically impossible to build. I used to tell him that he needed to do some time in a workshop. He'd just tell me to sort the practical details.
 
Hi Cam, 

Am really surprised you can't understand my maths.    surely yo can see the 1000 number relates to kg in a tonne?  its not rocket science!

Simple, 100hp -  250kg start weight  (bike 1) = 400hp / tonne
100hp - 200kg start weight (bike 2) = 500hp / tonne

For a 250kg bike to have a power to weight ratio of 500hp / tonne it would need  1000kg/500 = 2:1 kg/hp  so  250kg bike needs 125hp to reach a power to weight of 500hp/tonne

So loosing 50kg would in effect (and remember I said all other things being equal and simplified)  would be the same as adding 25hp to bike 1

Remember we are starting with bike 1 not bike 2,  so relatives are to bike 1. not to bike 2 as in your calculations.

The maths is 10/10 as the answer is correct,  Method is irrelevant!  unless I am in the classroom at school.
The classroom of the world = Win / loose  Answer right / answer wrong  ;)    Used to drive my teachers mad, but I always got the right answers!

Tyre grip etc,  well this could be long,  as in order to accelerate the heavier bike you would need all of that extra grip!  and as I am sure you know, the grip of a tyre does not go up in proportion to weight in a linear fashion for an astronomical amount of reasons, this is why wider tyres work and the reason it is easier to spin up the tyre on a heavier bike / car with a similar power to weight to a lighter vehicle.  Extra weight would also add more rolling resistance and so many other variables etc so not as simple as you put it either. 
To avoid getting into endless discussions that is why I said "all other things being equal"  of course they aren't but again the reality is mega extensive so pointless in this discussion.
Simply put, in "reality" a lighter bike has so many advantages and as any race designer will tell us, there are no significant disadvantages that would get even close to out weighing the advantages of weight reduction. 

Regards,
Jules

 
maybe the disconnect is because on bikes, typically one speak of HP/Kg (0,5HP/KG respective 0,4 HP/KG or even the other way around: 2 Kilos/HP respective 2,5 Kilos per HP). As Julian is coming from cars, the same in tons makes absolut sense.
 
Yep, lighter is better.

Finding the thin line where things start to break because they have become too fragile is the fun part. :D

piet
 
sfcpiet said:
Yep, lighter is better.

Finding the thin line where things start to break because they have become too fragile is the fun part. :D

piet
Click to expand...

Colin Chapman (lotus founder) used to say,  "if it breaks going over the finish line it was perfectly designed / prepared"    Not sure I would like to have been one of his drivers back then let alone race a Bike he prepared!!!  :o :o

Jules
 
Q,
I am going to use a 520 chain,  anyone got any experience racing with one of these,  they are used on all sorts of well powered mid range bikes nowadays so was thinking it should be perfectly ok if changed regularly.

J
 
My bike is equipped with a 520 chain ( DID 520 ERT 2), 3 years now in the German VFV/DHM.
No problems so far .
Michael
 
Fantastic,!!

Andy Chain,  How small can I go???  Change @ One race meeting per chain?  but a usable life of two?

Jules
 
Hi Julian,
I run 520 (Regina non 'O' ring purchased from Andy when he was still running his business) on my TT1 replica.

Its done two 4hr endurance races and a number of short circuit racing weekends, lasted well.

Andy
 
Julian,

I use a 520 DID non o-ring racing chain on my 215kg triple (a healthy 100+ ponies), running on an alloy rear sprocket.  It lasts well enough for a mix of track days and road use, I change it around somewhere around the 3000-5000km mark for safetys' sake.

We used to run the same chain on the H-D 883 Supertwins, these put out around 80-odd hp with weight around 180kg.  I replaced these after 2 races (3 training sessions, 1 race per event).  These bikes were tough on chains, no dampening elements in the drive train, vicious engine braking through the widely spaced gears.

piet
 
Great feedback guys, much thanks,
Will weigh up the chains and see what the saving is,  half of it is un-sprung so could be well worth the effort to go even smaller.
Big thanks,

Jules
 
Dellortoman said:
There are engineers who are academics and have never laid hands on tools, and there are those who have done some hands-on work.  I'm thankful that I'm the second type. I came from a trade background before I did an engineering degree.

I've worked with the academic type and sometimes it's hard to explain real world issues to them. I once had a boss who was like that. He was a clever bloke who had two degrees - a PhD in physics from a University in India, plus an electrical engineering degree from a university in USA. He'd actually worked for NASA for a short time when he was in USA. He could speak several languages and had written a bunch of academic papers. But I don't think he'd ever so much as picked up a screwdriver. He'd design stuff that was physically impossible to build. I used to tell him that he needed to do some time in a workshop. He'd just tell me to sort the practical details.
Click to expand...
Apparently that was the problem with Zane built bikes, young inexperienced ?engineers? straight out of uni who thought they knew better than the guys who had been building the Breganze bikes for donkeys years.
 
Andy J said:
Apparently that was the problem with Zane built bikes, young inexperienced ?engineers? straight out of uni who thought they knew better than the guys who had been building the Breganze bikes for donkeys years.
Click to expand...

There were very many people who built Breganze bikes in Zane.
At least part of the problem was management.

Paul
 
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