Team Go Dog, Go! Modified Partial Streamliners

[Seldom Seen Slim]

Whaddaya mean, "obscure publication"?  I was going through that very paper, saw that very photo, just about ten minutes ago.  Does that mean I'm "obscure", too?  Nancy, what do you think?

[wobblywalrus]

Thanks for the compliment Mr Bearisto.

The frame is back from the painter.  They used an epoxy primer.  I asked for that.  Usually I use zinc chromate primer and I want to experiment.  The top coat choice was theirs.  They used urethane enamel for the color coat and clear over that.  The paint matches the original Yamaha Fire Red.

Years ago I had two Matchless 500 cc single cylinder bikes.  A 1948 and a 1953.  One was made at a time when chrome and nickel were scarce.  The rims, spokes, and almost everything was painted.  This worked OK.  The zinc plating is gone from a lot of the parts on this bike and they will be painted silver.  Its a budget thing.  The parts need to be stripped of rust before painting.

The wire wheel on the bench grinder works good for the big parts.  It is dangerous to clean the little ones on the wheel.  These grit impregnated bristle brushes on the drill press work good for the small ones.  I use them with a slow speed of 280 rpm or a moderate 560 rpm.  They are much, much, safer than a wire wheel.  The grey one is coarse, the orange one is intermediate, and the blue one is fine.  All are needed to do good work.  Usually I use the coarse one to remove the rust and the finer ones to polish out the scratches.  The drill press table is set at a height where I can rest my wrists on the table when I am holding the part against the brush.  This gives better control. Grease and dirt can load up these brushes so they do not cut.  It is best to clean the part before the brush work.  These are Nyalox brushes made by Dico products in Utica, New York.  I got them at the local Ace Hardware. 

[bak189]

Question Wobbly!!......seeing that you make your own fairings and you race at the BUB meet....why not build a Dustbin fairing for your bike??....................................................................................

[wobblywalrus]

These Hinckley Bonnevilles have a tendency to speed wobble on deceleration.  Not just mine, my friends also have this problem.  The fairing weight makes it worse.  Some changes to the steering geometry, radial tires, proper suspension setup, and how I ride can manage the problem, but not completely cure it.  The weight of a dustbin might make the bike unrideable. This is what I worry about.  I get up to speed and I cannot shut the bike down without the death wobble. 

   

[bak189]

OK. I understand......see you at the BUB.....

[wobblywalrus]

Bak, I have a problem and a plan.

My friends deal with the Triumph wobble when they street race.  One bought a pair of upper tubes from "Forking by Frank."  I am not sure if Frank's stocked these or if he had them made.  He installed them with "gold valves."  I am not sure what they are.  The tubes have thicker walls, they flex less, and they help him a lot.

The standard Triumph fork springs are too soft and they sag excessively.  I bought a set of progressive springs.  All "off the shelf" racing springs for these bikes are progressive.  I much prefer a stiffer than standard straight rate spring.  IKON in Australia built the rear shoks and they did a good job.  They make custom springs.  A set of heavier straight weight fork springs should be no problem for them.

There is a frame modification used by the folks that road race these bikes in the Thruxton Series.

These four front suspension mods, reshaping the lower part of the fairing to modern practice, and fabricating an airbox to fit the flat slides will keep me busy and out of trouble for this year and next.  This 865 cc engine has 70 horsepower and it can have 80 with some fiddling and bigger valves.  I want to spend a few years on chassis strength and aero before I monkey with the motor.   

[stay`tee]

These Hinckley Bonnevilles have a tendency to speed wobble on deceleration.  Not just mine, my friends also have this problem.  The fairing weight makes it worse.  Some changes to the steering geometry, radial tires, proper suspension setup, and how I ride can manage the problem, but not completely cure it.  The weight of a dustbin might make the bike unrideable. This is what I worry about.  I get up to speed and I cannot shut the bike down without the death wobble. 

   

Wobbly, i can see that you are attempting to cure the handling problem, and that  is the correct move,,, however, in the short term, have you tried pulling the bike down from speed by applying the back brake (back brake only) while still holding power to the motor, then slowly backing out of the throttle, only shutting the throttle completly off once the bike is below the "wobble" zone ?,,,
This method has always worked for me, both on the street and dragstrip, whenever a machine has got the "death shakes" or had a flat rear tire, ,,,

[bak189]

Back in the 1970's I rode a Vincent with Brampton forks on the salt.....when I shut the bike down after
a fast ride (125mph?) it would go into a "wobble"....using the rear brake to drag the bike down and leaving some power on worked (as has been noted) needless to say I rode the bike only a couple of times.....
we changed the front forks to Vincent's later model....and had no more problems........we even got it up to
140mph

[wobblywalrus]

I will remember the back brake trick.

Today I looked at the Vincent Girdraulic fork in my old books.  I know that they work well, but I cannot figure out why.

[wobblywalrus]

Today I called Forking by Frank in Evanston, Illinois.  They made the stronger fork tubes that my friend uses.  Frank's told me the original equipment Triumph inner tube wall thickness, and theirs, too.  Some quick figuring is needed to show if the benefits are worth the effort and expense.

The calculations assume the ability of the tube to resist flexing is directly proportional to its moment of inertia around an axis through the tube center.  This simple assumption will work for this application.  The old and new forks will differ in the inner tube inside diameter, only.  Their lengths, etc will not be changed.  It would be possible, using much more complicated math, to compare the flexural properties of a change in fork length and wall thickness.

The new tubes will resist flexural bending 19 percent better than the old ones.  This is a substantial increase in strength in an area of troublesome weakness.  I will order a pair.

[Old Scrambler]

Good advice on the tubes...........since you are ordering a pair.........have you considered the length?  Maybe you would want to change the front wheel size (taller and more narrow rim) and adjust for frame height with shorter tubes. You may only want to run the rear brake. In '09 BUB I helped (block of wood) remove the complete brake system from the front of the electric bike. Next day they ran 10mph faster with no wobble.  Just a thought........you seem to ride it well!

[wobblywalrus]

This morning our Triumph club had its monthly breakfast and I talked to people with experience.  The Triumph fork tubes are unusually thin for a bike of that weight and speed. The thicker tubes will be similar to what most bikes are using.  This year the stronger tubes are what I will do.  Cost is a big issue.  The fix can be done for between $300 and $400.  This I can afford.

The sun came out today and it quit raining for a couple of hours.  I almost forgot what the bright shiny fellow looks like.  Summer is on its way.  I hope it arrives soon. 

 

[wobblywalrus]

The Old Scrambler has an excellent idea. A fork length change to accommodate a different size wheel.  In this case I would go to a smaller, rather than larger, front rim.  There is a 19-inch spoked rim on the bike with tube type tire, now.  A 17-inch rim has these advantages.  There are many more choices in high speed rubber.  There is less gyroscopic effect with a smaller wheel.  There are "mag" wheels in the smaller size, and this allows tubeless tires.  This would eliminate the tube weight and it would be safer.  Tubeless tires tend to deflate at a slower rate when punctured.

Simply fitting a 17-inch wheel on the front would drop the headstock an inch, it would steepen the steering angle, and trail would be decreased.  All of this would hurt stability.  Fitting the 17-inch wheel with an inch longer fork will preserve the current steering geometry.  Stability will not be compromised.  The fork tubes will be raised an inch in the triple clamps until I am able to get the money for the smaller wheel.  I will lower them when I fit the new hoop.

One problem I will have is the spring preload adjuster on the top of each fork tube.  There is no room for them when the tubes are raised an inch.  The handlebar gets in the way.  I must remove them.  This is a problem.  I run maximum spring preload when the fairing is on the bike.  This keeps the proper ride height with the added weight.  I use the minimum preload setting when the fairing is off.  This makes the ride a lot smoother.     

 

[Old Scrambler]

We all know that the basic law of physics requires reaction to change. If you are suffering fork sag......a simple solution is a 2-step process........heavier fluid and a slight overfill.  Spring preload will shorten the overall potential travel but they should never fully compress. Preload alone tends to lead to a bound spring situation which typically results in a wobble because no two springs are absolutely equal.  Your fairing is not only adding weight but it adds substantial down-force at speed. The effect has been measured by just adding a small fly-screen.

Regarding wheel and tire size...........I like tubeless for safety, weight, and availability.  I like tubes on skinny TALL rims for soft track conditions because they roll easier and ADD gyroscopic effect to counter any shift in weight.  Smaller wheels steer quicker but this is straight-line riding. Their is a wide selection of modern 21-inch tires with speed ratings of 130 and up.  Maybe I am wrong, or don't competely understand the physics, but dirt-bike riding and observing my fellow riders tells me that wire spokes and aluminum rims are lighter than cast.   

[wobblywalrus]

We got the seniority list at work last week.  Basically, they give this to us before the layoffs.  For once in my life being old is a good thing.  I am not at the top of the list, but close to it.  This always bothers me.  The first to go are the young guys and gals.  They are our future.  Heck, I would retire early, except I have children at home and an expensive hobby.  That 19-inch "paid for" front wheel is looking really good right now.  It will be on that bike for a looong time.

Frank's wanted me to send in a fork tube so they could match it.  No problem, I pulled one off.  The front wheel and fender need to be removed to install the fairing.  This is a perfect time to fit the new tail and reshaped front.  I did this, put on the monkey suit, and climbed on.  The front view is shown.

Several things are apparent.  First, I need to increase the front coverage.  This will be done next year.  Second, I need to tuck in my toes.  Third, look at my eyes.  They can barely see out from under my lid.  I cannot get down and lower and still see where I am going.  The helmet blocks the view.  Is there a good helmet that gives forward vision for a guy tucked down low?  See the side view.  I need to get lower.