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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 518607 times)
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wobblywalrus
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« Reply #2610 on: October 29, 2016, 09:41:17 PM »

Mike, it should be the strongest engine I can afford to build.  The fellows in AUS are building some very radical engines with the balancer shafts removed, very big valves, polished and knife edged cranks, and lots of RPM, more than 10,000.  They will have the strongest engines.  My approach is to have a well balanced package with a combination of a good engine with decent streamlining and lots of experience with running the thing.

Neil, I do not know how to figure that effective length either.  A simple stack with 1/4 inch radius on the flange helps.  My guess cannot be off more than 0.25 inches, probably.

Dennis, There will be two headers for the dyno work.  One will be this one untouched.  Another will be one I make according to the computer program.  They will be quite different in dimensions.  I cannot weld anymore so I need to find someone to make the computer pipes.           
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wobblywalrus
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« Reply #2611 on: October 30, 2016, 10:43:05 PM »

There are two cam grinds I can use.  One is web cam #813 and I have been using it for years..  it has 629 degrees duration at .050 per inch of lift.  The other cam is a web cam #146.  This is the exhaust cam I used as an inlet cam.  It has 614 degrees duration at .050 per inch of lift.

The comp cam #9042 grind has the same base circle radius and it has 616 degrees duration at .050 per inch of lift.  This cam, with a 1.08 rocker ratio, gives a good representation of the #813 lobe.  The #9042 with a 1.17 rocker ratio closely resembles the #146 lobe.  This is the best I can do.  The comp cam is the only one I have with a digital profile.  Extensive computer modeling was done with these combinations:  #813 for inlet and exhaust, #813 inlet and #146 exhaust, #146 inlet and #813 exhaust, and #146 for both.

The #813 cam has .388 gross lift and the #146 has .420  I was expecting to see a big difference in performance.  Not so.  All combinations were within a horsepower of each other and all made peak ponies at 8,000 at 8,500 rpm.  Every time I tried to force peak power to occur at a higher RPM, the HP dropped off.

The #813 cams I have, they are in good shape, and they are broken-in.  The one #146 cam I have is galled along with its tappet buckets.  I need to get it reground, get another cam ground the same specs, buy eight tappet buckets, and solve the durability problem.  It is a no-brainer decision to stay with the old cams.

The Filling-and-Emptying model was used for all of this.  It assumes the intake and exhaust system are optimized.  It says 87 horsepower is all the flywheel HP I can expect at Bonneville with the intake and exhaust sorted.  This is my best estimate of the rear wheel HP on the dyno at Beaverton:  (87 / .86) x .9 = 91 HP.  The power I got last fall with those cams that were horribly out of time was 90 HP.  Something is goofy in the modeling.  The program cycles through all sorts of iterations and it lists the peak HP when it does them.  The peaks are in the 90's and they are a lot higher than in the final result table.  Somewhere I am losing all sorts of power.
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wobblywalrus
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« Reply #2612 on: October 31, 2016, 09:26:41 AM »

The program has a feature that optimizes cam timing and duration for a given lift.  That is how the lobe center angles are calculated for the actual cams.  The optimized cams have the best timing and duration.  They gave power in the mid to high 90's.  The cams I put into the model at those optimized lobe center angles are the comp cam profile with rocker arm ratios to enhance their lift.  Unfortunately, the duration was not enhanced proportionally.  The HP output with them in the model is in the mid 80's.  That is is why I lost all sorts of virtual HP.  I need to wait until I get the digitized profiles from Kibblewhite before I do anything.  This rocker ratio enhancement trick does not work.
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wobblywalrus
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« Reply #2613 on: November 01, 2016, 12:06:25 AM »

A call to Arias asked about piston speed.  There is no problem with running these slugs at high rpm.  Average piston speed at 10,000 rpm is just under 4500 feet per minute.  That seems like a good rev limit so the igniter boxes will be reprogrammed for that.  They are at 9,000 rpm now.  Another call was made to web cam.  One of the ladies calculated the cam durations at .006 lift for the #813 cams I am using now.  She also told me about a #208 grind that has a bit more lift and duration than the 813, but it is not too radical.  Also, I mentioned my idea about using thermal barriers on the valves and running them with tighter clearances.  She said it seems OK.  The cams were modeled with typical Bonneville atmospheric conditions.  Flywheel HP is 80 at 7,000, 83 at 7,500, 87 at 8,000, 88 at 8,500, 88 at 9,000, 88 at 9,500, and 85 at 10,000.  This assumes the intake and exhaust system are optimized.  This is a nice spread of power.  An advantage of good HP at high rpm is that it allows higher gearing ratios and this, combined with the horsepower, will give a lot of tractive force.

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wobblywalrus
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« Reply #2614 on: November 02, 2016, 12:52:22 AM »

Lots of late night trial-and-error modeling did the job.  The ghetto blaster low budget motor is designed.  Fast and cheap.  The dream build is next on the drawing board. 
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« Reply #2615 on: November 02, 2016, 07:55:10 AM »

Quote
An advantage of good HP at high rpm is that it allows higher gearing ratios and this, combined with the horsepower, will give a lot of tractive force.

Once again, HP = force x velocity.   For a given velocity and a given force (drag), all you need is a certain horsepower.  A wide spread of power is nice since it minimizes the hole between top and next-to-top gear, but if all you need is 88 hp, why spin the motor to 9500 if you can get 88 hp at 8500 (or 87 at 8000)?  It makes no difference in tractive effort--88 at 8500 starts out with more torque which is then acting through taller gearing.
Unless one is attempting to minimize driveline capacity (size/weight), there is no particular reason to go to the high speed, low torque route.
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« Reply #2616 on: November 03, 2016, 11:52:08 PM »

IO, you are correct and my thinking was goofy.  That is good 'cause rpm = $$$.

Right now I an dealing with a packaging issue.  It seems that short and fat headers, collectors, and meggas do the trick.  Cramming them inside the fairing is an issue.  Some guys in the Triumph factory built a special engine with the cylinder head on backwards.  There are merits to this.  It makes it easier to use correctly sized exhaust pipes.
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« Reply #2617 on: November 07, 2016, 01:28:28 AM »

The advice I get from Kibblewhite on intake cam lift is to look at the flow data and the last lift increment before further increments do not give significant increases.  Then, intake cam height should be 110 percent of this, as a general rule.  This would be 0.400 x 1.10 = 0.440  The cam in the bike now has 0.380 lift so it is a bit short.   Webcam makes an intake cam with 0.400 lift and they sent me estimated 10-point data.  It was modeled in Dynomation this weekend.  A lot of effort went into optimizing it with a 9,000 rpm rev limit.  It was modeled with my old 0.380 lift exhaust cam.  They make an exhaust cam to go with it that has higher lift.  It will be modeled next. The results from the .400 intake and .380 exhaust are on the attached.



* 2017 Build 056.PNG (59.73 KB, 1017x607 - viewed 56 times.)
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wobblywalrus
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« Reply #2618 on: November 10, 2016, 11:13:06 PM »

The engine simulation program has an option to optimize lobe center angles using a simplified emptying-filling model.  The exhaust system types are input and the model assumes they are optimized.  It gives realistic lobe center angles for the application.  Usually this is 100 to 105 for the intake and 110 to 115 for the exhaust.

The intake and exhaust systems are not optimal due to packaging and lack of $$ factors.  The actual intake and exhaust characteristics are entered into the program.  The more complex wave-action model considers the intake and exhaust characteristics as input.  It optimizes cam centerline angles considering this.  It gave me these nice and high HP results in the previous post.  Note the horrendously large overlap.  The lobe center angles are tight, like in the 80's and 90's.  The program is optimizing the lobe center angles to my goofy and compromised intake and exhaust systems, is my figuring.

There will be structural problems with these tight LCA"s, like valves hitting each other and the piston crown.  Now, the lobe centerline angles are optimized using the filling-emptying model and those recommended values are used throughout the remainder of the virtual build.
 
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wobblywalrus
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« Reply #2619 on: November 11, 2016, 02:07:52 PM »

The rough draft engine design is done.  It gives me 15 to 20 HP more than I had on the high end.  The best cams are skinny with moderate lifts.  Going wide on duration or tall on lift costs HP.  Now I will order the cams with digital profiles so I can make a more accurate virtual model.  Right now, the design is done using 10-point cam descriptions and this in not the most accurate method.  The lobe centers are wide enough so the valves will not hit the pistons or each other.


* 2017 Build 057.png (394.63 KB, 1024x724 - viewed 52 times.)
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« Reply #2620 on: November 11, 2016, 02:47:25 PM »

What would the virtual performance be if you reduced the collector from 3" to 2.5"?
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2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2016 AMA Record - 750cc M-CG HONDA CB750 sohc - 130.7 mph
2016 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 137.7 mph
Chasis Builder / Tuner: Dave Murre
wobblywalrus
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« Reply #2621 on: November 12, 2016, 01:33:36 PM »

Collector diameters were modeled from 2-5/8 to 3-1/4 inches ID in 1/8 inch increments at 5,000 through 10,000 rpm.  Power was the same at 5000, 5500, 6000, 6500, 7000 and 8000 rpm.  There was a one HP difference at 7500, 8500, 9000, and 9500 rpm.  There was a two HP difference at 10000 rpm.  These are the differences among the entire range of tested diameters.  These differences are small and it is likely something else in the system can be adjusted to compensate for the loss caused by a 2.5 inch dia collector.  This virtual engine with the cams and lobe center angles used is not sensitive to collector diameter.

This is a Cosworth style engine with two exhaust valves per cylinder and it has very good flow at low lifts.  A short duration exhaust cam with a wide lobe center angles is used to prevent rapid bleed down of cylinder  pressure at exhaust valve opening.  A two valve per cyl engine would be a slow old three legged dog if it used the design specs for this engine, intake, and exhaust system.       
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wobblywalrus
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« Reply #2622 on: November 15, 2016, 08:22:22 PM »

www.bbc.com/earth/story/20161114-from-planet-earth-ii-a-baby-iguana-is-chased-by-snakes  Land speed race is a big deal for that little guy.  We have it pretty easy.
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wobblywalrus
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« Reply #2623 on: November 22, 2016, 09:57:41 PM »

That movie with the iguana reminds me of tech inspection.

The step header and collector I ordered are used on flat track bikes that run the mile.  Dirt track racing requires a flat torque curve so the engine produces predictable power over a wide range of rpm.  The dimensions and sizes are input into the virtual model and, sure enough, that is the power it makes.  What I need is maximum power on top end and different dimensions and tubing sizes are needed.  Also, pipe mounts and the megga need to be made.

Burns Stainless makes the parts I need to do the work in 304 stainless.  Some way to glue them together is needed.  TiG welders cost a lot and I do not have much $$.  The shed is wired for single phase 220V.  This was done in anticipation of getting a welder.  The Lincoln 180C Mig welder looks affordable.  Is there a big advantage to TiG for light duty work like welding sheet metal and general bike related fabrication?     


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« Reply #2624 on: November 22, 2016, 10:23:25 PM »

A tig offers much finer control and neater, higher quality welds. Look for a tig welder with available high frequency AC and you'll be able to weld aluminum as well. Mig welding stainless requires a very specific gas mixture. One of the best sites to learn techniques is weldingtipsandtricks.com .

Pete
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