Bottlehead race sponsorship
- Thread starter Doc B
- Start date
Yeah I have lost weight since I got those leathers, and it's time to go back down a size or maybe just get them altered. They will roll over from Snell 2010 to Snell 2015 helmets next year so that means a new Shoei X-14 too (cripes they are expensive). It's been three weeks so naturally I already have the bike completely reconfigured in my head to run fuel class next year - three spoke wheels, adjustable clipons, lose the lights, aero fender, 6" rearsets, seat 3" back, tanks for gas, nitrous and alcohol injection, crossover pipe, beefier oil pump, lighter valves, titanium keepers, beefier clutch, etc., etc. I suspect I'll need to get to at least 110 to record in 350 M-CF which means finding around 20hp. Tricky, but possible. Option 2 is look for more low hanging fruit in a different class and get a different bike. Already have my eye on one possibility.
When you crunch the aero/hp/speed numbers weight reduction has about the least impact. Reduced frontal area is way more influential, as is reducing drag coefficient. My estimated speed was pretty accurate using about 555lbs, .7 Cd, 6 sq ft frontal area. Figuring about a 20% hp loss at 5000 ft I would have been putting out about 25.5hp, which would have put me right about 90 mph. I was up to speed at the timed mile even with a semi-slipping clutch, so I was probably OK in terms of accelerating my mass in the run up. Running 50 lbs lighter would have gotten me to maybe 90.1, but reducing frontal area by 0.5 sq.ft. could get me close to 93. So tighter leathers and getting more tucked and skinny are probably more useful than chopping weight off the bike, for sure.
Look up Alp Sungerteken. He just ran 173.33 against a 123.869 record in SCTA 650 M-VF, on a naked 1950 Triumph 650 running nitro. Holy s**t!
When you crunch the aero/hp/speed numbers weight reduction has about the least impact. Reduced frontal area is way more influential, as is reducing drag coefficient. My estimated speed was pretty accurate using about 555lbs, .7 Cd, 6 sq ft frontal area. Figuring about a 20% hp loss at 5000 ft I would have been putting out about 25.5hp, which would have put me right about 90 mph. I was up to speed at the timed mile even with a semi-slipping clutch, so I was probably OK in terms of accelerating my mass in the run up. Running 50 lbs lighter would have gotten me to maybe 90.1, but reducing frontal area by 0.5 sq.ft. could get me close to 93. So tighter leathers and getting more tucked and skinny are probably more useful than chopping weight off the bike, for sure.
Look up Alp Sungerteken. He just ran 173.33 against a 123.869 record in SCTA 650 M-VF, on a naked 1950 Triumph 650 running nitro. Holy s**t!
Paul Joppa
Moderator
I'm on vacation, and we spent yesterday in the Greek National Archeological Museum. Here's wikipedia on an example of reduced rider weight for speed, from about 150BC:
https://en.wikipedia.org/wiki/Jockey_of_Artemision
:^)
https://en.wikipedia.org/wiki/Jockey_of_Artemision
:^)
![20180919_182038[1].jpg](/data/attachments/6/6498-20e65386b1068021eb5682fc084fef83.jpg?hash=r-26izupPp)
I'm running in what is called a naked class. That means no front fairing, which is generally considered to be worth about 5-15 mph. So the aero treatment body-wise is limited to what you can do to the front fender and what you can do to the seat. Other than that it's all about reducing frontal area, rider position (a.k.a. tuck) and maybe lengthening the wheelbase up to the allowed 10% to improve the Cd a little. There are a zillion other little details, like tight leathers, proper gearing, etc. to obsess over. And horsepower (a.k.a. where the bulk of the money goes). I'm deep into beefing up my motor for this August, so I can give it a much bigger shot of nitrous than last time without breaking things. At least that is the theory. In 2019 I put a valve adjuster screw through a valve cover on my third run.
Here's a video of my second run from 2019, with nitrous injection, a better clutch and a bit more practiced technique. Once I'm on the bottle I'm running about 10 mph faster than in the previous video. Hoping to add another 5 mph this year.
https://youtu.be/38aD32y6wbI
Here's a video of my second run from 2019, with nitrous injection, a better clutch and a bit more practiced technique. Once I'm on the bottle I'm running about 10 mph faster than in the previous video. Hoping to add another 5 mph this year.
https://youtu.be/38aD32y6wbI
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I have considered it. Like putting VGs along the edges of my arms and legs and at the hunch in my back. The math for the speeds I run works out to the vortex generators being about 1/32" tall or something equally silly. There was a time a few years ago that one of the pro cycling teams had little bumps on the arms of their jersey sleeves. The calcs for that kind of stuff at cycling speeds are like you gain .3 seconds over 30 miles.
One thing I plan to try down the road is lengthening the rear swing arm 5", which would allow me to create a relatively long tail on the back of my seat the width of my butt and tapering back to and end even with the rear of the rear wheel. That is one of the few aero things allowed in my class and it should help improve Cd. The old saw in land speed circles is "Don't worry about the hole you open in the air. Worry about how well you close it."
My plan for the past couple years has been to use photogrammetry to model the bike and me in my leathers. I imagine you know about the online CFD analyzers like simscale. My hope is to get a decent 3D model and run a CFD analysis of different riding positions, components, etc.
One thing I plan to try down the road is lengthening the rear swing arm 5", which would allow me to create a relatively long tail on the back of my seat the width of my butt and tapering back to and end even with the rear of the rear wheel. That is one of the few aero things allowed in my class and it should help improve Cd. The old saw in land speed circles is "Don't worry about the hole you open in the air. Worry about how well you close it."
My plan for the past couple years has been to use photogrammetry to model the bike and me in my leathers. I imagine you know about the online CFD analyzers like simscale. My hope is to get a decent 3D model and run a CFD analysis of different riding positions, components, etc.
