Team Go Dog, Go! Modified Partial Streamliners

[wobblywalrus]

My SCTA rule book is paid for and ordered.  The bike number plates are tonight's project and the rule book is not here yet.  So, a question follows.  The FIM race numbers are 6 inches tall, 3 inches wide, and the writing is 1 inch thick.  They are placed on a background with contrasting colors.  White numbers on a black background are what I use now.  Will this work for SCTA?

[salt27]

Per the 2020 SCTA rule book. 7.B.1

"Numbers shall be a minimum of 3 inches high by 1 inch wide, class designation characters shall be a minimum of 1 inch high; both must contrast with the background on which they are applied."

[salt27]

More,

"Number/class may be applied to a surface on the motorcycle or number plates may be used.
Number plates shall be securely mounted with a minimum dimension of 6 inches by 8 inches and a maximum dimension of 10 inches by 12 inches with a corner minimum radius of 1 inch.
Number plate location is dependent on specific class rules."

[wobblywalrus]

Thanx for the help.  It took some juggling to fit 150 mm by 80 mm FIM numbers on a 12-inch long SCTA size number plate.  The rivet lines tell a story.  The almost horizontal and rightmost vertical lines were the edge while running in AMA MPS class.  The vertical line to the left of the MPS line is for the tail with AMA APS.  A piece of metal was spliced onto each side to convert from Modified Partial to Special Partial streamlining.  The AMA APS rules were changed and the bike was illegal for the class.  The mods to make it legal were ones I did not want to do.  The tail was changed to FIM partial streamlined dimensions by adding the extension onto the end.  It is the newer and shinier aluminum.

The SCTA rule book has not arrived, yet.  The goal is to bolt the number plate onto the tail in a location where it will not be disturbed if the tail is cut to SCTA dimensions.  What are SCTA tail dimensions in APS class?     

[salt27]

7.G.11

"The seat/tail section cannot extend further to the rear than 10" beyond the rear edge of the rear tire.

No part of the seat/tail section may be more than 40" above the ground with the rider seated.

No part of the seat/tail section behind the rear axle may be closer than 4" from the ground with the rider seated."

Bo, I'm about 100 miles south of you.
  You are welcome to borrow a rule book if you want.

  Don

[wobblywalrus]

Thanks for the offer of a rule book on loan.  My copy should be arriving by mail, I hope, soon.  I can wait for it.

The tail tip is OK for FIM but not for SCTA.  I will drill out the rivets and remove it after BMST and before World of Speed.  The number plate is in a place where it can remain undisturbed.

[wobblywalrus]

There was a post by JimL awhile ago.  It mentioned how silicone spray residue can keep paint from adhering to a vehicle.  This method is based on that concept.

An old number sticker needed to be removed from the tail.  It was held down by adhesive on the back of the paper and it was covered by clear packing tape.  Acetone was used as a solvent to soften the glue and make the sticker and tape easier to remove.  The problem was the acetone evaporating away before I could scrape off the glue.  The glue would smear around and it would reattach to the aluminum.

The sticker and tape were soaked with silicon spray.  Then acetone was applied and the sticker and tape were removed.  The silicone film prevented the glue from reattaching to the metal.  This sped up the sticker removal process. 

[wobblywalrus]

Is there a way to attach a .mov file? 

[wobblywalrus]

This is the smoke test.  It was done before any changes were made, like me crouching in a lower position, taping up the leathers. etc.

https://www.youtube.com/watch?v=6_LW-2f8KUA

[ggl205]

WW, what were the lift number coming off tunnel tests?

John

[wobblywalrus]

Lift was a problem with the first front end on the fairing and it was redesigned to give more downforce.  The later version is what you see in the movie.  These Triumph Bonnevilles have the typical rearward weight bias of bikes built in the older days.  They do not have the forward weight bias of the newer sport bikes.  A full tank of gas helps the weight distribution.  The front end never has a secure and planted feel while racing.

The trail needed to be increased to get steering stability.  It could have been done by raking out the front end or by reducing triple crown offset.  Reducing offset was what I did.  It is a better way to get the needed trail on a bike with a light front end, in my experience.   

The fins and spoilers on F1 cars hang out into the breeze.  They create massive amounts of aero drag and it takes a lot of horsepower to get the downforce when they are used.  Reshaping the front of the fairing gave downforce without significantly increasing rearward turbulence so that is what I did.

I thought I lost the tunnel data forever due to my lack of ability to organize files.  The movies were found a few days ago and I will look for the data printout.

[wobblywalrus]

This is the first page of tunnel data.  Run #5 is the one I am building to.  This is lower seat position, tighter leathers, closed tail, and no speed hump on the leathers.

[wobblywalrus]

This is page 2.  The lift data is in the first columns to the left.

[wobblywalrus]

This is the third page.  I am not sure if 0.27 lift vs drag is a desirable value.  In fact, I do not know much about any of the numbers on this spreadsheet.  My elementary understanding is the goal is get the lowest Cd.

[ggl205]

WW, chart #3 looks like a continuation of chart#2. I saw those C fields from the Darko tunnel as well but told to ignore them.

Good data on chart #1. Appears tucking the helmet as low as possible yielded greatest benefit but I bet you figured that before the test.

One of my tunnel tests was to extend the tail three feet and complete the tapered aero feature. We cut cardboard to kick up the bottom, figuring this would help Cd. It did not but finishing the taper did.

John