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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 548884 times)
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wobblywalrus
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« Reply #615 on: December 08, 2011, 12:53:15 AM »

Thanks, Grumm.  I will get an SCTA rule book.  Hopefully the bike rules are more simple than the car ones.     
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grumm441
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« Reply #616 on: December 08, 2011, 03:58:01 AM »

Or you could just
http://www.dlra.org.au/rulebook.htm
Never mind
G
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Chief Motorcycle Steward Dry Lakes Racers Australia Inc
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I build it, Goggles tries his hardest to break it
wobblywalrus
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« Reply #617 on: December 09, 2011, 12:35:32 AM »

Thanks, Grumm.  I will download it when I figure how to get my computer working OK.  I was planning on running at speed week before AUS.  It would be interesting to pull out a DLRA rule book in the SCTA tech inspection to discuss if something was legal.
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grumm441
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« Reply #618 on: December 09, 2011, 04:53:17 AM »

Yep
Funnier still is when you get to tech inspection and get the same inspector you got in Aus grin
G
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wobblywalrus
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« Reply #619 on: December 12, 2011, 01:35:19 AM »

The same inspector would be nice at both events.  Speed week will be 2013 or 2014 and AUS in 2015.

An airplane wing slices through the air.  The air pressure over the curved upper surface is less than the corresponding pressure under the flatter lower surface.  The high pressure air under the wing swirls upward into the low pressure air at the wing tip.  There are swirling eddy currents in the air where the wing tip has passed.

It takes energy to move air.  The household fan is an example.  No air moves unless that rascal is plugged in and turned on.  The swirling eddy currents are air movement, it takes energy to cause them, and this energy loss is interference drag.

The goal of streamlining is to save energy by moving as little air as possible the shortest distance, and energy is saved by minimizing interference drag.  To do this, the surfaces are designed to have similar air pressure on them.  The curvature, texture, length parallel to the flow, and angle to the air flow is as uniform as practical.  It took me a long time and several tries to get concept from theory to bent and mangled sheet metal.  One side of the fairing is made, as shown in the photo.

The steering stops were shimmed to give me 15 degrees of movement on each side.  I sat on the bike and turned the bars.  A little bird on my shoulder said "You have been here before.  You told yourself you would never do it again."  In my distant memory there was a bike with limited steering swing.  It was terrifying to manoeuver around at lower speeds.  I went really slow and paddled a lot to keep it from tipping over.  The steering lock is 25 degrees each way normally and I will keep it that way.  The hole in the fairing is sized to give enough clearance.  The steering is at full lock and the fork is completely compressed in the photo.  There just enough room to accommodate the fender.


* Fairing Rebuild 100.JPG (224.58 KB, 800x533 - viewed 138 times.)

* Fairing Rebuild 101.JPG (165.66 KB, 800x533 - viewed 144 times.)
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Koncretekid
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« Reply #620 on: December 12, 2011, 07:14:22 AM »

Excellent work, Bo,
I have a couple of thoughts.  A Large hole in the front can cause a lot of drag from what I've read (Bradley, for example).  The famous Can Am 125 didn't have any hole in the front - - it certainly worked for them (of course the motor seized on the return run).  Can you close part of the hole to reduce this drag?  Possibly with some screw-in panels; start without them and watch the temperature gauge.  Then close them up and try again.  NASCAR cars do it with duct tape and it speeds them up.  I don't think it matters what their shape is (curved or flat).
Tom
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We get too soon oldt, and too late schmart!
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wobblywalrus
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« Reply #621 on: December 12, 2011, 10:12:03 PM »

A fellow a few years ago was running a naked Triumph with an engine build similar to the one I am doing.  He forgot to shift into 5th gear and made the run in fourth at high rpm.  The head cracked.  Knowing this, my plan is to run the hole open until I learn how to do data recording and I get some baseline information about engine temps.  Then, after looking at the data, I will close up the hole a bit at a time if I can.

Another thread on this forum discusses crankshaft configuration.  I posted some info about work I did to the Triumph crank to prepare it for high rpm use.  A reply mentioned road racing Triumphs and 10,000 rpm engine use.  It would be unfair to hijack the other fellow's thread.  Info on this subject follows.

Currently my target rpm is 7,500 and the rev limiter is set to 8,400.  This is higher than the standard Triumph factory red line.  It works OK.  These engines are very strong.  Reciprocating engine parts are subject to stresses when they are accelerated and decelerated.  Forces create these stresses and they can be roughly approximated by the equation F = MA where F = force, M = the part's mass, and A = acceleration.   Acceleration can be approximated by A = V**2 / 2g where A = acceleration, V**2  = velocity squared, 2 is what it is, and g = the gravitational constant.  Basic algebra shows that the internal stresses in an engine increase in proportion to the rpm squared.  In other words, doubling the rpm increases the engine stresses fourfold.  This is a rough and simplistic statement.

In these calculations from a few years ago, I see that increasing the engine operating speed 1000 rpm increases stresses 25 percent and increasing the rpm ceiling another 1000 rpm will increase stresses over 50 percent.

Horsepower can be calculated by the equation HP = t x 2 x pi x rpm / 33000 where HP = horsepower, t = torque, 2 = two, pi is pi, and 33000 is a constant.  Assuming that the torque is the same for all engines, some bonehead algebra shows us that horsepower is directly proportional to rpm.  In other words, double the rpm will double the torque.  Again, this is a simplistic statement.

This is some of the most useful info I can calculate.  In Case 2 the engine operating speed is increased 1000 rpm, engine stresses go up 25 percent, and I get 13 percent more power, 77 horses.  In Case 3 the operating rpm is raises another 1,00 rpm, engine stresses go up a whopping 54 percent and I get a measly 86 horsepower. 

Big increases in engine stresses = periodic teardowns and inspection + regular replacement of some very rare and expensive parts.  The roadrace folks do this.  They have no choice.  Some LSR people with big money take this route.  My budget says a higher 8,000 rpm target rpm with a 9,100 rpm redline is OK.  It increases stress about 12 percent and it will give me a few horses.

These simple equations explain why blowers, turbos, fuel, and combinations of all three are so popular.  They can provide much more power than spinning the engine faster.   


* Rev Calcs 1.jpg (115.99 KB, 600x752 - viewed 123 times.)

* Rev Calcs 2.jpg (113.79 KB, 600x781 - viewed 143 times.)
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wobblywalrus
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« Reply #622 on: December 15, 2011, 01:32:37 AM »

The RPM vs stress calculations showed me that high engine speeds cause greater inertial stresses.  These are the stresses caused by parts moving back and forth.

Therer is another type of stress in an engine and it is caused by the pressure of the combustion in the cylinder.  It compresses the piston crown, the rod, the crank bearings, etc.  These stresses can be reduced by increasing the rpm.  The work of moving the bike is spread over more engine revolutions.

Right now I am planning for a new motor.  The tradeoff of greater inertial loads and reduced combustion pressure loads at increased rpm is keeping me busy. 
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« Reply #623 on: December 15, 2011, 08:00:00 AM »

"double the rpm will double the torque."  I'm sure you meant "double the rpm will double the horsepower."  Of course this assumes that torque remains the same as the rpm increases.  In real life, torque begins to drop at some point due to reduced efficiency.  Therefore, horsepower doesn't always increase proportionately.  So you have a double wammy -- increased stress without the proportional increased horsepower.  Cubic dollars spent on porting, bigger valves, bigger carbs, different cam timing, more efficient exhaust and so forth sometimes add up to a small gain.  That's life!

Does the Department know you're using their notepads?

Tom
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wobblywalrus
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« Reply #624 on: December 15, 2011, 08:55:14 PM »

The mistake is mine.  I meant to say double the rpm doubles the HP assuming the torque is the same.  Usually I do my calcs on toilet paper in the john.  These notepads are a big step up to classy behavior.

A call from the vendor selling me the big bore cylinders started all of this figuring.  The pistons are custom made and he wanted to know the CR I wanted, 11.5 to 1 or 14 to 1.  The 14 to 1 is the best for a racing engine to be used at B'ville.  It will work well with racing gasoline and the thin air on the flats.  The choice was easy.  11.5 to 1 will work for a street motor near sea level and this is what I chose.  The second question was about ring thickness, 1 mm or 1.5 mm.  I would chooe the thinner rings for a high rpm drag motor or B'ville only engine.  The thin rings resist flutter at high rpm.  I chose the thicker 1.5 mm ones.  They wear better and I will not have a high rpm engine.  The vendor asked what I would be doing with the motor.  I said "street use with annual runs on the salt."  I should have been more specific and told him about the horsepower I wanted and the red line.  Rick Vogelin's "The Step-by-Step Guide to Engine Blueprinting" has a chapter on pistons and rings.  It tells a person about the various setup choices and what they do.

Inspired by all of this, I got out some old calcs and started to do some serious figuring.  I made a lot progress in learning about engines.  I made greater progress in confusing myself.  In a moment of clarity I called Triumph Performance and said "the power and torque curve on your website for the 104 horsepower engine is what I want."  The curve is shown and it is in the "Bonneville" portion of the "Performance" section.  It is for an engine with a big block and a stroker kit.  Mine will have the big block, only.  About 90 hp is all I expect.   


* Jumbo Motor.jpg (185.1 KB, 1024x744 - viewed 128 times.)
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wobblywalrus
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« Reply #625 on: December 22, 2011, 02:04:00 PM »

Happy Holidays from the mouse patrol and Team Go Dog, Go!


* Shop Katz.JPG (361.23 KB, 1024x693 - viewed 116 times.)
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JimL
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« Reply #626 on: December 23, 2011, 06:31:45 PM »

I can certainly attest to the difficulty of getting the horsepower gain out of the 5 digit RPMs.  My project is down to jumping compression, shorter tuned lengths, and reducing internal losses.  It is becoming difficult to tell where remaining horsepower may be hidden, because small tuning problems seem to be amplified up there above 10,000 - 11,000 RPM.  Next year will require some changes in the ERC gasoline choice and engine temps.  I dread that experiment (has to happen because I've shortened the stroke.)  It is very hard to find that edge without stepping in cracks a few times, and they don't make parts for my old engines, anymore.

Always fun keeping up with your build!
Regards, JimL
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wobblywalrus
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« Reply #627 on: December 24, 2011, 12:58:31 AM »

Jim, you are in a more difficult position than I am.  You are exploring the outer limits of those little Honda twins.  The 90 horsepower big bore motor I will be building is a mild engine.  Sometimes I think chopping up one of those new Kawasaki 1,000's into a 500 cc twin might be an answer.  The more I look at that concept, the better it seems.   
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wobblywalrus
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« Reply #628 on: December 26, 2011, 12:27:05 AM »

A new windshield was going to be made for the rebuilt fairing.  That was the original plan.  No money for that now and I will try to use the old one.  It is a Triumph windshield that says "PC" near the recycling triangle.  This means polycarbonate, I think.  The new fairing is wider than the old and I need to flatten out the windshield a little bit.

First, I perched it over the wood stove and put a couple of logs in.  The windshield was heated up by the stove and it was warm to the touch.  I spread it apart and it sprung back.

Next, I placed it over an Alladin oil light.  These put out a lot of heat.  I could not get the windshield hot enough to bend and stay bent.

Has anyone bent one of these?  How hot should I get it and how is it usually done?


* Attempt to Bend.JPG (230.17 KB, 617x600 - viewed 114 times.)
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Peter Jack
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« Reply #629 on: December 26, 2011, 01:03:16 AM »

Be careful because polycarbonate is Lexan or actually viseversa. It contains water and will bubble before it reaches bending temperature. Scratch one windshield. It requires a slow prebake in an oven to expel the moisture. I've found the required temperatures and times on the internet before. Get Mr. Google busy and follow the instructions or next thing you know you're going to learn how to build a new windshield...................not good.

Pete
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