Scooterotica

dave wheeler wrote: group 6 bikes are so fast because of there shape and lack of resistance to air flow

just to be clear group 6 has more to do with engine spec as far more is allowed regarding tuning ... a ts1 is not allowed in group 4 for instance

dave wheeler wrote:to come up with an equation that would tell you how much power is required to propel a given shape

See Stokes Law and derivation of a Reynolds Number. Hard sums - specially when you have little data.

RICSPEED wrote:i have seen charts relating to bhp / speed / drag factor ... think the rule of thumb is something like " to double the speed your need four times the power "

Pretty much.
Frontal area and "slipperyness" or how smoothly the air can flow round a given shape. Well you can crouch down, lowering the frontal area and also improve the shape, probably better than the old knacker bike in the example I gave earlier. Time trial cyclists have those weird helmets and bikers have the hump ...
In order to meet imposed fuel consumption targets, car manufactures did lots of research, finding surprising levels of improvement in quite small changes - smaller panel gaps for example. You'll have noticed in F1, all panel joints are taped up and not to stop them falling off. So shoving your toes or elbows out, not to mention all the other stuff - bin liners and the like - all pushes up the hp requirement. You can swan about all week at 60, then at the week end load up with the aformentioned stuff, try to do 60 for miles on end, but the power requirement is now much greater, engine working harder, and pouff, no forward motion, no compression or no turn over, no fun.

well let me state the obvious you can only do 70mph on the road so whats the point of having a scoot that can go 100mph
































































ill get me coat

rules are there to be broken gimp ,its cool to be a rebel if everyone had the same bikes that did the same the roads would be a very boring place :baddevil:

eden wrote:

Daz Kane wrote:this is not a road going scooter is utter b@11@x, just tax and mot it, then it is. :fb:

Tax and mot it and do 500+ miles on it over a weekend to a rally with luggage etc and then it is! taxing and moting it and going to the paper shop on it and then calling it a road going scooter is utter bollox :fb:

, this was the point i was trying to make eden, although not very well! I know of two BSSO lambretta group 4 bikes which are still running the same gearing and piston set up for last two seasons, and are still competitive. you can have a standard scoot that won't do 500 miles with luggage on, going to rallies that will still break down! a pointless thread as 100+ scooters have been around for decades, the problem is the technology is some 60 years old, tuners are tying different ways to get round this, but the frames were designed for 11bhp not 40bhp. As for reliability - no two engines are the same, even if there built the same, then there the 'bell-end' sat on it! happy scootering :fb:

Regarding the RB250.........yes it got to over 90mph but in the test drive in scootering wasn't the rider told to "back off" when reaching a certain temp? Whats the point of that!

Yeah, you could tax and mot a race scoot but......they are jetted and the timing is set within the finest margins to get best power over a particular track. Hold one of those at full throttle for a few miles when its been jetted and timed for 200 yard straights and your gonna go pop!
Same with compression etc. To make them viable as a rally scoot your gonna take hp out of them to leave safety margins and they are also run on higher octane fuel are they not?
High speed touring would be great but 100mph on 10 inch wheels for a long period of time.....i'd s~~t my pants!

uffy is a friend of mine and speaking to him at cadwell was geared for approx 90mph/95mph with approx 35bhp on a lightweight group 6 but with panels so probably represents normal conditions which snett with a tailwind isnt
ive had a play on my drag race sim and found you only need a tailwind of 16 mph to achieve 113.5mph with only 35bhp so as i said in a previous post if you drag race/or race regularly enough then 1 day that tailwind will be there for you to achieve that good result but the 2 way records events will show the true speeds

nelson pk wrote:Regarding the RB250.........yes it got to over 90mph but in the test drive in scootering wasn't the rider told to "back off" when reaching a certain temp? Whats the point of that!

note in darrels chart ... friction .. thats another factor to throw in the pot .. ( friction = heat )

raypeed race with a standard fan set up ( imho to test the kit for road riders ).. all the other group 6 * use lc be it just head or full water jacket barrels

* mine dosent ... yet !

RICSPEED wrote:

nelson pk wrote:Regarding the RB250.........yes it got to over 90mph but in the test drive in scootering wasn't the rider told to "back off" when reaching a certain temp? Whats the point of that!

note in darrels chart ... friction .. thats another factor to throw in the pot .. ( friction = heat )

raypeed race with a standard fan set up ( imho to test the kit for road riders ).. all the other group 6 * use lc be it just head or full water jacket barrels

* mine dosent ... yet !

I've been looking for the article to read it again but it might not have been in Scoootering. The reason he was backing off was because it hadn't been run in from what I remember and the journalist rider did nip it up but Ben did get it to 93+ (GPS) without nipping it up or something like that.

Interesting Ton up, on the road on a Lambretta

I would like to say that if you have the power to pull the right gearing and the length of road plus the right exhaust it would be possible,

But you guys that have been 80 -90 mph GPS will no how scarey it is and unsafe also sounds like your engine is going to go bang any time LOL

so I think you would have to be talking Dyno but as we no all dyno's read different

anyway i think lets all keep safe and stick to 70 -80 GPS which is fast enough