2nd 100cc APS build

[55chevr]

If you use the fence top rail in the background as a guide you can really appreciate the way Cliff's back is straight and he at least 4" lower than I am.  His torso is not resting on the frame which levels his back .... David 's photos are something else.   Almost like a training manual.

[sofadriver]

Just picked these up on flea-bay. Almost new  Bates 2-piece in a drag racing cut (should be perfect). Worn for just one race. Guy swears he never even sweated in them. (I didn't know you could pull the trigger on a 6 second drag bike without sweating!   ) He's the same size as me. $255. A good deal I think. No problem passing SCTA tech. I can sell my track suit for that much (darn thing shrank around the waist!   )
http://thumbs.ebaystatic.com/d/l200/pict/261723909647_1.jpg

Got the frame back and tried the normal "feet/knees under me" position. No can do. Besides lots of pain and not being able to breathe, it puts the width across my knees at 25" which is way too wide. That's OK. It turns out the Kamm tail opening is going to be smaller than I expected so I can live with it.  It's good to know that all the time I spent sitting on the can engineering this thing wasn't wasted  

[Kiwi Paul]

You probably should have parked it somewhere else to take your photo. The writing on the ground isn`t such a great indication of the project and it`s direction....

[sofadriver]

Ha!  Good point! 

[wobblywalrus]

An hour ago I sorta came to the same conclusion about having your back level.  Forty years ago it was not uncommon to see a rider lift his arse and make his back level on the straight away at fast tracks.

My neck and back are stiff, too.  There are some yoga exercises you can do to increase the flexibility in the parts of you that can bend so as to partially offset the stiffness of other areas.  Once I get the bike built I go out and sit on it in the race position for a few minutes every day.  At first it hurts and is difficult to do.  After awhile it gets easier and you will tuck down lower.

 

[sofadriver]

My daughter is in to yoga and says she'll get me straightened out. I have been working on my posture, too. I'm not a slouch but I could be better. The goal is not to have to lift my glasses up higher by taping them to my forehead (folks who wear glasses know what I'm talking about)

From the start, I've had doubts about whether the RS125 forks were going to be long enough to allow me to look over the tire but under the bottom fork tree. Now that I've had a chance to check the front suspension sag and mock up a fender I can see I'm going to need longer forks. I'm headed to the local m/c junkyard today.

[sofadriver]

I picked up a set of late 80's Honda 250 Interceptor forks for a reasonable price. The stock RS125 forks are only 24" overall. The Interceptor's are 32". I mounted the new forks and found that an overall length of about 28" works great. Far better forward vision and they increase the caster by 6 degrees. Wheel base increased to 72". Since they're softer sprung, I now have some sag on the front forks, too. No sag at race weight had me a little worried since I had no downward suspension travel.

One of the sliders fits the RS125 axle just fine and the other will work with minor machining.

That still leaves the forks sticking out of the top trees by 4". They'll be sticking into the airstream at that height so that 4" has got to go. I took them apart for cleaning and the first part I found under the end cap was a 4" spacer on top of the springs!  Cool!  Now I just have to cut 4" off the stanchions, rethread for the caps and put them back together without the spacer. 

 

[wobblywalrus]

Some of us need to look over the top of our glasses when our head is down low.  The limiting factor is the brow of the eye port on the helmet.

Years ago I was told to make sure the front fairing gave me frontal coverage when I was on the bike in a position I could actually ride in, rather than one I hope to assume.  Experience on rough tracks showed me that I have a hard time when my chest is on the tank.  I get bounced around a lot and it is hard to keep balanced to ride in a straight line.  The best position for me is with my belly resting on the back of the tank and my chest slightly above it.  My head stays relatively stable so I can concentrate on keeping the bike on line.

Rose took pictures of me from the front when I was on the bike.  Using those, I sized the fairing so it gave me coverage.  My hands, shoulders, etc are all behind it.  Only the top of my helmet sticks out above the top of the windshield.  The trailing edges of the windshield and fairing were made as close as possible to being parallel to the long axis of the bike where the are broke off of their trailing edges.  Now I had a fairing to give me coverage.  Fairing surfaces were carefully looked at to minimize those that would give me lift and to maximize the those that would push the front end down.

Not done yet.  It was time for fine tuning the front shape and incorporating the tail.  This is where the NACA profiles were looked at.  The top and sides of the bike have different profiles.  The fairing shape was fine tuned to make the best use of a NACA profile.  The tail was done last and it followed a NACA shape as far back as it legally could.  This is 1/2 the rear wheel rim diameter past the back of the rear tire, for FIM.  The front fender was also looked at and shaped to blend in with the front of the fairing.

The front of my fairing looks too be too big.  Note on today's post about Erin Hunter the size of the fairing on Andy Sill's bike.  Current thinking is to have a good shape and coverage as opposed to a smaller shape with less than optimal coverage.

This might not be the best way to do it, but it worked for me.               

[sofadriver]

Some of us need to look over the top of our glasses when our head is down low.  The limiting factor is the brow of the eye port on the helmet.

Years ago I was told to make sure the front fairing gave me frontal coverage when I was on the bike in a position I could actually ride in, rather than one I hope to assume.  Experience on rough tracks showed me that I have a hard time when my chest is on the tank.  I get bounced around a lot and it is hard to keep balanced to ride in a straight line.  The best position for me is with my belly resting on the back of the tank and my chest slightly above it.  My head stays relatively stable so I can concentrate on keeping the bike on line.

Rose took pictures of me from the front when I was on the bike.  Using those, I sized the fairing so it gave me coverage.  My hands, shoulders, etc are all behind it.  Only the top of my helmet sticks out above the top of the windshield.  The trailing edges of the windshield and fairing were made as close as possible to being parallel to the long axis of the bike where the are broke off of their trailing edges.  Now I had a fairing to give me coverage.  Fairing surfaces were carefully looked at to minimize those that would give me lift and to maximize the those that would push the front end down.

Not done yet.  It was time for fine tuning the front shape and incorporating the tail.  This is where the NACA profiles were looked at.  The top and sides of the bike have different profiles.  The fairing shape was fine tuned to make the best use of a NACA profile.  The tail was done last and it followed a NACA shape as far back as it legally could.  This is 1/2 the rear wheel rim diameter past the back of the rear tire, for FIM.  The front fender was also looked at and shaped to blend in with the front of the fairing.

The front of my fairing looks too be too big.  Note on today's post about Erin Hunter the size of the fairing on Andy Sill's bike.  Current thinking is to have a good shape and coverage as opposed to a smaller shape with less than optimal coverage.

This might not be the best way to do it, but it worked for me.              

EXACTLY !
One of my goals has been to have textbook aeros. Sill's bike looks big but that's what textbook aeros look like.


I'm almost ready to copy the bike, and then the bike with me on it, onto a sheet of plywood that I have marked in 1" grids. Easy to do with a framing square and a helper. Then I'll draw naca0021 around the bike/rider shape, cut it out and mount it on the bike. Then the fun begins.

https://us-mg5.mail.yahoo.com/ya/download?mid=2%5f0%5f0%5f1%5f183735%5fAERUimIAABA1VLiLzgGGoPyLOVY&m=YaDownload&pid=2&fid=Inbox&inline=1&appid=yahoomail

[55chevr]

The fairing size and shape has to consider the rider.   Factory fairings on crotch rockets first consideration is that they are designed to sell motorcycles.   Aero is a secondary consideration.   

Joe

[Seldom Seen Slim]

I need to wear glasses to see down the road/the course, and I need bifocals so I can read the gauges.  So -- if the glasses are correct for seeing where I'm going - the reader part is too far down the lens for me to use it.  So I had the eye doc grind the reader parts as high up on the lens as the shop could do them.  They were weird for reading - around the house, for instance - but on the bike, head tilted and helmet on and so forth -- wow -- I can read the tachometer!

Moral of the story:  Don't be afraid to ask the doctor or the whomever if you can have something special-made to fit your particular need.

[Nortonist 592]

Back in the 70s there was an English snooker champion by the name of Dennis Taylor.  He wore glasses and snooker requires a heads down, eye along the cue type of playing.  Not totally dissimilar to what you are doing.   He had special frames made so he could see when his head was down level with the cue.  Something to think about.

[maj]

Looks like he just turned them upside down

[Nortonist 592]

Looks like he just turned them upside down

It does but they were special made for him.

[sofadriver]

Geez, I thought that was Mrs. Doubtfire!
I knew an electrician that had bi-focals on top and bottom. I've wished I had them many times, especially when working on the boat. I need frames that have a taller viewing area without looking like I'm lost in the 70's (again  )

Started the mapping process today but didn't have a helper to map the rider.