Monday, December 1, 2014

125CC Wind Tunnel Test 2011

After we returned from Bonneville in 2010 I needed to know what the Coefficient of drag was on our bike. We poured in 400 hours or so with design, carving, sanding etc. and wanted to quantify the hard work and begin applying some science rather than just gut instinct to the project. Remember, the goal is to be the first 125cc streamliner to top 200MPH. So along with testing the current bike i planned on a test of our 200mph streamliner as well. This would be achieved using the current bike and covering the rider area with cardboard and tape to finish out the shape. The bike's cross section is nearly identical to my streamliner design. Even though its about 38 inches shorter it should give us a rough idea of where we are at. The added length of the actual streamliner will ultimately make it even more slippery.
An acquaintance from Texas who had already done some car testing in the tunnel brought in some experience which turned out to be very helpful in terms of process and recording the data.
It turns out matte board and tape go a long way in the tunnel allowing for quick changes yet provide enough detail to record change, for the better or worse. The following photos and video show the bike in different test modes and I will do my best here to point out what is happening.

First test is the Full Streamliner mockup:

We record a coefficient of drag of .078 which is really low but not entirely realistic as there are no vents for air intake for cooling and the pressurized air-box but nonetheless we find it encouraging. The BUBS streamliner in the same tunnel recorded a .080 C of D! Amazing considering how much larger it is and its a complete functioning motorcycle unlike our humble mock up. Hats off to you Mr. Manning.

After the full streamliner test we start peeling away pieces of cardboard section by section and running the tunnel each time we remove something. Remove one item at a time and you can clearly see if it works or not. We peel away until we get down to the bike as it was run in 2010.
This is what i was most interested in; what is the C of D on the current bike? Lets look at the infamous smoke test as the visual it quite entertaining. After all the testing recorded on the tunnels scale they slow the wind speed down and allow the smoke to tell a visual story which makes it all a bit less abstract. I don't have the patience to edit the video so feel free to bail at any point during the 5 minutes of wind and smoke.
As you can see in the smoke test we do fairly well with laminar flow. Yes seperation is happening after the riders body but the smoke is still visible unlike most partial streamliners where it dissapears entirely. The bike as we ran it in 2010 ends up with a Cof D near .34. With further tweaks like the cardboard on the front fairing by the helmet and shoulders, we get it down to .312. The tunnel operator casually mentioned this was the lowest figure ever recorded for a partial streamliner motorcycle in the A2 tunnel. We also find out airbox pressure is outstanding with gains to be made with a radiused entry lip. Clay was very helpfull in modeling the test lip on the airbox entry.

If you look closely in the video you can see the black and white clay used to fair in the edge of the windscreen. The plastic windscreen has always been screwed to the outer surface of the front fairing leaving an edge .062 tall exposed to the oncoming atmosphere. I agree...horrendous. But fairing in the windscreen to be flush with the fairing is a great deal of work and i wanted to be sure it was worth doing.
Crikey! .011 decrease with the clay which correlates to .5hp. On a 125cc motor you can't afford to give away any horsepower as they are too hard to come by and by the time we are done there will literally be no ponies left to buy. Fast forward to a photo one year later of the faired edge for the windscreen prior to paint. A word from the wise man is sufficient.
The most important lesson to be gained from this blog entry; Spend money at the tunnel before spending it on your motor. Way more bang for the buck!
Next time we will cover the applied bodywork modifications gleaned from the tunnel test as we prep the bike for our 2013 effort along with some mechanical changes as we look to simplify the process of running the bike at Bonneville.

Wednesday, March 26, 2014


Truth is...they are all team efforts. From a MotoGP weekend in Japan to an amateur motocross race at Loretta Lynn's ranch in Tennessee. It starts with Mom and Dad and or an Aunt and Uncle along with
a friend who owns a motorcycle dealership or raced when they were kids and now jump on the bandwagon of joy derived from the team work of a race weekend. Yes that's a little bit corny and a run on sentence but it's rotten in truth and I fucking love it! Did i mention i had to go to summer school sophmore year for English?

So before we move forward to the extra juicy bits, wind tunnel testing in 2011, a 50HP Rotax motor in 2012 and the record setting run at Bonneville in 2013, I give you a brief run down of what we were after and what we finally achieved in 2010.

Now one of the records that has eluded us since the beginning of this '125cc Partial Streamliner' journey has been held by Robert Barker and his Can Am team since 1973! Nice piece on the factory effort here; Can Am 125cc Land speed record Sweet bike and an equally sweet T-shirt. Something tells me there is a mustache hidden from view.
I had the pleasure of meeting Mr. Barker in the pits at Bonneville, he mentioned they did not run a radiator back then and it made me wonder about the few horsepower you might give up with head temp going over 45C, the temperature where you start leaving horsepower on the table. A hot head versus the horsepower loss due to water pump drag and or radiator drag. We had already ditched the radiators and i find it hard to believe the water pump eats 3.5 HP which is the equivalent HP loss if hitting 80C which is easy to do. Maybe its all a wash but i am more comfortable pinned at 150 knowing the engine is most likely a bit happier operating at the temperature it was designed to run at.

Now onto the racing!
First fill the on-board Tupperware container with ice to ensure the copper tubing that runs from the motor and through the ice keeps the head cool. Also make sure the blue Tec-Nec tape is in place to keep the feeble adhesive backed foam insulation from peeling off of the tupperware ice cooler and speculate if tape anywhere else on the bike or on your person will help you go faster.

Physically exhaust all team members in helping to push start the bike then feebly slip clutch all the way to starting line while negotiating starting line position with +-7 degrees of steering. Then wave exhausted helpers back to lift the rear wheel up to get the bike pointed in the right direction and curse yourself for building  a bike with +-7 degrees of steering.

And finally;
Give it a handful and break a 37 year old land speed record! Now you have to wonder what took so damn long to break it. In the words of Dennis Manning, "You have to go faster than the fastest bike that ever was." I paraphrased a bit but you get the point. All you have to do is eclipse another team/maniacs effort and your in the record books. Sounds easy!

Saturday, February 15, 2014

Bonneville 2010 Yahoo!

So we left off with the bike having been roughly assembled after getting the bodywork back from paint. Chris Cosentino swung up to finish assembling the air-shifter he designed and fabricated, while we started to pack up the trailer. Fast forward to the salt and the bike looked something like this:

Once again we had a punch list to address which burned most of Sunday and half of Monday. The darn thing just wouldn't steer and would flop over the second you started to correct the steering. The harder i tried to ride the bike the worse it got. We fixed it, with three solutions all happening at once on our makeshift workbench so it was hard to say which solution was the effective one. So the three steering solutions were:

1) Reverse the steering linkage; Why pray tel? The bike was originally steered with two vertical levers/handlebars connected to the steering arms via push-pull control cables. Note the black control cable in the picture above, this is the original chassis from 2006. I was never thrilled with this system even though it was mechanically very convenient in connecting point A to point B. There was about .125 of play in the steering system due to the cables movement in the cable housing, it worked and the play was hardly noticeable at speed, but it bugged me.

In this photo you can see the cables have been replaced by rigid aluminum rods with rod end bearings at either end providing a very direct link to the steering arms with no slop in the system. If you look closely you can see the original mounting holes for the steering linkage at the bottom of the handlebars which is below the pivot which was correct for the steering cables but not the rods. The rods needed to clear the moving swingarm so the steering arms were rotated 180 degrees and now reside above the swingarm reversing the input movement. Here's the rub; i kept the same mounting points on the handlebars so the steering is now reversed. I didn't think this would be an issue as most steering input happens on this bike with body english and i figured i would get used to it. So we moved the mounting point above the handlebar pivot point. While i don't think this was the culprit it certainly didn't hurt. I would like to move the rods to the originol mounting point, to reverse the steering, as an experiment next time we are on the salt.

 2) Adjust the trail; Prior to arriving at the salt I decreased the trail from 5.0 to 3.5 inches as an experiment. On the right side of the front hub, see photo above, there is a tab pointing downward which is welded to the wheel spacers. These white spacers key onto the kingpin/steering axis and by rotating the spacer the kingpin angle changes which changes the rake which in turn changes the trail. The original chassis was slow to react to steering input, no doubt the low center of gravity played into this as well. With the new longer chassis I feared the extra wheelbase and weight would make it steer even slower so i thought less trail might speed up the steering a bit but it didn't seem to be working so we added 2.0 inches of trail . Again, like the steering linkage I'm not quite sure if this was the solution as i have not played with this adjustment on its own. If it ain't broke, don't fix it.

3) We found black rubber on the interior of the fender where the tire was rubbing. I believe this 'smoking gun' is what steered us in the right direction, excuse the pun. The bike had no self righting characteristics and and as i mentioned before would just flop over once the front wheel received or didn't receive input. The wheel was binding up enough to stop self righting but not enough to lock it up.

After all three changes were implemented we had a motorcycle that steered really well. The following video shows before and after; before i was sick to my stomach and after you will see i am happy enough to run around in circles. The team worked really well through this problem and we beat it.

It took a couple of runs to figure out the shifter system which needed a battery and CO2 giving us two more variables to contend with. Simplicity had always been the mantra when designing the bike but this added complexity seemed necessary due to the ergonomics involved at the footrest area. Shifting up and down with a thumb push of a button was really cool, Thanks again to Cosentino Engineering.
That's me and Cosentino in the photo, I'm really happy with the shifter and he.......well he looks uncomfortable.
Next blog entry, we set a record!

Sunday, January 19, 2014

Why 125CC?

THIS    2011 Aprilia 125cc SuperMartXe' VIP Team / Paris Hilton.


There are many good reasons why we run a 125 at  Bonneville or on the track, here are a few:
1) My buddy Dwight had a 1996 Honda RS125 motor in my shop and it sounded like a good idea to build a land speed bike for this motor.... but it's actually much deeper than that...
The reason there were 125cc bikes in my shop was due to the acknowledgment by my friends that the only way to find out what it is like to ride a race-bike is through riding a Honda or Yamaha 125 or 250 GP bike that has been imported from the land of the rising sun. The key letters being GP, that is Grand Prix, the real McCoy, the shit. And in the words gleaned from an English cooking show, its fookin' pukka. I assume that means genuine or awesome. anyway...I had the good fortune of running a friends 96' RS 125 and within two laps i understood what they were getting at. If you have never had a go i highly suggest seeking one out at a track day and begging for a spin, like we used to do when the first dirt bike showed up in our neighborhood as kids.
2) This next bit is really going to offend the majority of racers: Street bikes converted into race bikes, and or track day bikes, are fookin' pigs. I don't care how much money you spend making the bike lighter and quicker it will never equate to the riding experience undergone while riding a purpose built race bike. Once I was tuned into this my track life changed for the better. It turns out this might be the least costly way to race and or do track days, the 125 that is-a 250 not so much. More on that later, for now a brief and slightly informed history of why the 125 is such a noble steed.

3) This is a 1996 Honda RS125 2-stroke GP motor. It weighs only 38 pounds and in a mild state of tune puts out 42HP at the rear wheel. A more potent, slightly more modern, and an extremely more expensive version might put out as much as 55HP at the rear wheel! With a proper chassis a complete bike weighs in at 150 pounds and in the GP stables they weigh even less. This is one reason a 125's corner speed is greater than a 600 and a 1000cc superbike, its all about the power to weight ratio. (Note: this is based on observation and hearsay, i have no actual speed gun readings of pro riders all going through the same corner on said bikes. If you have that info please post a comment so i can be humbled or more confident in my corner speed arguments.) Our current land speed bike weighs in at 200 pounds even, not bad for a motorcycle with a 104 inch wheel base.

Some historical perspective; I recently read Kevin Cameron's' book, 'Classic Motorcycle Race Engines' and discovered that Suzuki's GP125 single in 1962 had the same bore and stoke as the modern GP motors. That's fifty years ago! It was air cooled with a rotary valve and produced 22HP and would get up to 30HP after two more years of development which included water cooling. The bore and stoke of the Honda motor pictured above is nearly identical to the fifty year old Suzuki RT62 at 54mm x 54mm, and while this similarity might be layed in bedrock as a perfect engineering solution to what is needed from a 125, it most importantly bolsters our desire to get the most out of a historically significant displacement. Keep in mind this single cylinder format would be doubled and doubled again to create 250 twins and 500 fours, all three sizes becoming the GP standard race classes in the modern era of GP racing.

4) The 125 format is just plain handsome in its simplicity. This jewel is our newest 125cc motor which took us to a top speed of 155MPH at Bonneville last year with a new AMA record of 149.907. With 48HP at the rear wheel at sea level and probably 42 or so at Bonneville elevation we are nipping at the heals of bikes with 8 times our displacement. We will be running the bike on the dyno to verify these dubious horsepower figures next month. The Rotax bottom end design goes back to the 80's i believe. The Aprilia cylinder and BRC head are both from the last 5 years or so.

So for all the dopes who have made faces and or scoffed at what we do at Bonneville, history and the pragmatic engineering of a 125cc 2-stroke motor is on our side while we very quickly approach the AMA land speed records of most 600cc four strokes and have surpassed all but two of the 1000cc AMA records held by Harley Davidson's. Two more miles per hour and those two Harley records are done for. That might sound childish but I can't wait!

A lucky 15 year old Maveric Vinales' adds two more good reasons to race 125's..........