Vespa Dry Lake Racer lives...

[grumm441]

I'm just thinking of scrutinnering
And that hole in the back of your leathers if for???
G

[internetscooter]

Quick update - still progressing slowly on a CFD modelling and I am also working on a onboard computer for monitoring acceleration etc i.e. calcuate +HP (power) and -HP (drag) directly. So I can predict what I should see in a computer model and then validate that against what I actually see. Also if luck is on our side we'll have our own dyno to validate further!. When I iron the bugs out I'll post more details as it is software that would work for bikes too
http://www.vespalabs.org/Projects/Scooter_Computer_II

Also I had the story of the 2009 attempt gathering dust on my harddrive, so I pulled it out and stuck it up on the web (Some of the pictures C/O Peter Quick). So if you missed the Scootering article you can now see it here:
http://www.internetscooter.com/index.php?title=Scooter/Dry_Lake_Racing/The_World%E2%80%99s_Fastest_Vespa%3F

[internetscooter]

Latest news...

Short version:

wound her out to 99mph, no chance of 100mph but with long 4th gear (exhausting all gearing options) I reckon I have a 50/50 chance of 100mph

Long version:

The latest dyno run was done on the new Scooterlabs dyno, which is a dyno setup to read true rear wheel HP (not estimated at the crank). On previous dyno runs I had issues with mapping the rpm correctly due to various reasons (e.g. dyno setup for standard Vespa gearing and then I hop on with my long gearing). Also all dyno runs were done in third gear. So the lab session was to do a few things:

1) Wind her out in 4th gear and see what the top speed is based on mph alone (not post-calculated from rpm)
2) Do the dyno with the tyres pumped up to race pressure
3) See how the tyres handle 100mph

The results:



1) Blue is 3rd gear, Red is 4th gear. Even with a Malossi 24/63 upgear, the current peak power (32hp) is at ~86mph (7500rpm) fading out (21hp) at around ~95mph (8500rpm). With no juice at all by 100mph (just under 9000rpm).
2) The increased tyre pressure and reduced rolling resistance gave a peak power of 32hp at the rear wheel (which on dyno's that estimate crank hp would read 42hp)
3) The rear wheel (and the rest of the motor) handled the speeds fine
Note: I estimate that 25hp is required to do 100mph

Also noted that my rpm gauge isn't as bad as I thought - 9000rpm seems to equal 9000rpm

Conclusions:

* Get a DRT 33 Tooth Long 4th Gear, with this longer 4th gear I will locate peak power @ ~91mph, fading out at around 103mph.
* A better and shorter carb manifold which is less restricted will push out the top end rpm
* The super charger planned may also push out the top end
* Maybe a 35mm or 36mm carb would improve power, the 38mm may(?) be too much. Though with a super charger probably not
* Maybe alter the expansion chamber to drop the top end power more slowly (diffuser taper angle) or target higher rpm (length)

Due to kids and family sickness I probably won't make 2012 but may make the Longford Festival

[RGV]

Great results Paul, im sure you will get to your goal. Sorry to hear you cant make it to 2012, we need more 2 strokes

[momec3]

Interesting results and a tidy curb. Having spent lots of time with chassis dynos the obvious effects of tyre rolling restitance are pronouced with anything with smaller horsepower. Extreme example is putting big off road tyres on a small engine 4x4. They can eat as much as 30% of the power. Anything you can do with friction reduction gives a much bigger percentage pay off with a small motor compared to a big motor.
Good work Paul, your onto it.

Chris

[internetscooter]

thanks - I also just did some extra calculations on piston speed. I am nicely in the safe zone up to 10,000rpm with less that 3800 ft/m (20m/s) and at 11,000rpm I am still sort of ok at 4000 ft/m (22 m/s). So nice to know, especially since I have rev'd out it to 10K in 3rd So at least in this respect I can push out the top end safely.

[RGV]

Hey Paul what about putting some heat wrap on your chamber to increase the air temp?
Im sure you know the theory, be interesting to do a back to back on a dyno to see if it makes much difference.
Or put a smaller ID stinger on the chamber to lift cylinder temp, but not too much or the piston might end up dribbling out your exhaust.
Both will lift the RPM that the max HP is produced.
Just a couple of thoughts.

[penny]

Many if not all bikes that go in line at bonneville have a wet towel draped over the gas tank . As the purveyor of Ice at the lake for the club i would like to recomend this and maybe add a container of ice on top , Ice melts at 0 degrees centigrade and could only help any cooling effect .
Come see us for your supplies . paul.

[internetscooter]

what about putting some heat wrap on your chamber to increase the air temp?
Im sure you know the theory, be interesting to do a back to back on a dyno to see if it makes much difference.

Yes - I've heard about changing the tuning with water spray to cool and slow down the wave propogation. I really really really like the idea of a heat wrap!!! It looks easy and solves a number of other issues. I have built the exhaust articulated and inline with the wheels to reduce drag and improve handling (less unsprung mass and it brings the weight forward). The exhaust and other piping will eventually be enclosed in a fairing... wrapping will reduce the heat build up and protect things like water pumps. The other thing it does is hide my dodgey welds

Many if not all bikes that go in line at bonneville have a wet towel draped over the gas tank . As the purveyor of Ice at the lake for the club i would like to recomend this and maybe add a container of ice on top , Ice melts at 0 degrees centigrade and could only help any cooling effect .

Thanks - Penny - I am actually sitting on the gas tank - so it might make the ride a bit more comfortable too

I've access to the dyno on a regular basis so I will let you know how the heat wrap goes and I'll also try the ice when summer comes.

Cheers,

Paul

[momec3]

I wrap my fuel tank in a similar material for all those reasons. Helps keep the heat out to begin
Chris

[ROSS BROWN]

.....................METHANOL......................

[momec3]

Yeah Ross we know, petrols for washing parts.

Chris

[internetscooter]

yes the current scooter record (132mph) was done with Methanol.. took him a few decades to get there so I have a while to go

[momec3]

So skip the middle man and go straight to POP. Same class. Only one piston, buy a carton.

Chris

[internetscooter]

OK dyno'd the exhaust wrap tonight with some interesting results...

(Note: from a previous run, without the exhaust wrap, I was getting ~32hp.)

With the exhaust wrap the overall result was negative: less power (~28.5hp) and about the same rev range when the engine was at full operating temp (green line below).

However, when the engine was cool, again less power (~29.5hp) but not as bad AND the engine rev'd out to 104mph, with about 17hp at 100mph (red line below)

So it did something but it's not going to do much in a real race.



Next on the agenda is a better carb manifold (I'll put methonal somewhere down on the list behind a few other tricks I have up my sleeve )