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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 685226 times)
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wobblywalrus
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« Reply #2235 on: November 26, 2015, 12:22:37 AM »

The old engine that did 146 mph had pistons which were labeled 11.5 to 1 on the box based on the OEM combustion chamber. Two millimeter larger intake valves were installed.  The metal removed when this was done lowered the static compression ratio to 10.5 to 1.  The inlet valves were closed by the old cam at 49 degrees ABDC.  The dynamic compression ratio adjusted to Bonneville salt flat elevation was 8.43 to 1.

The new engine has pistons that are labeled 13 to 1 on the box based on the OEM chamber.  The two millimeter larger intake valves and the unshrouding I did lowers the static compression ratio to 11.8 to 1, estimated.  The new cam shuts the intake valves at 65 degrees ABDC.  The dynamic compression ratio adjusted to salt flat elevation is 8.47 to 1.

The hot cams need compression to make them work.  Both Vizard in his books and the Victory Library papers mention this.  I would have an awfully slow bike with very low dynamic compression if I did not bump up the static compression ratio.

The changes I am making are about the best I can do with a 995cc engine using an overbore to give the added displacement.  The fast guys install 4 or 5 mm larger intake and exhaust valves, open up the combustion chamber so the valves are not shrouded, and increase the engine stroke.  The stroker motor crams more displacement into the larger chamber and a radically domed piston is not needed.  A flat top one will do.  Their engines are far to big to race in the 1000cc class.

This build diary is good reading for someone who is building one of these engines.

     
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Koncretekid
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« Reply #2236 on: November 26, 2015, 08:21:33 AM »

quote:"The new cam shuts the intake valves at 65 degrees ABDC"

At what lift is your cam spec?  I'm curious because Megacycle uses .040" for the BSA but .020" for early triumphs, so hard to compare.

Tom
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wobblywalrus
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« Reply #2237 on: November 28, 2015, 09:57:09 PM »

The cam specs are proprietary and I cannot give details.  The calculator is "Harley Advanced Dynamic Compression Calculator" at www.rbracing-rsr.com/calculations.htm  It is handy.  It tells me I need between 1 to 2 pounds of boost to make the bike preform on the salt flats like it does down in the Willamette Valley where we live.
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wobblywalrus
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« Reply #2238 on: November 28, 2015, 10:03:50 PM »

It is hard to compare cam specs between 2 valve per cylinder BSAs and older Triumphs and the four valve heads on these new Triumphs.  Four valve heads require different cam characteristics.  Vizard discusses this in his books.
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wobblywalrus
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« Reply #2239 on: November 29, 2015, 03:21:02 PM »

Crankshaft modification to reduce windage is a current topic among a few of us bike builders on this forum.  The crank shown is unmodified and it is used in the scrambler.  It will be the crank in the turbo motor.  The one I am modifying is similar except the crankpins are at 360 degrees rather than the 270 degrees for the scrambler.

The thicker counterweight will be chamfered like the ones on the Wolfenden crank.  The thinner counterweight will have its leading edges radiused like on the other crank.   


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Koncretekid
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« Reply #2240 on: November 29, 2015, 05:11:40 PM »

Bo,
Will balancing be a problem on your 360 crankshaft if you knife edge the counter weights to that extent?  Is your motor wet or dry sump?
Tom
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wobblywalrus
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« Reply #2241 on: November 29, 2015, 06:42:03 PM »

It is wet sump.  These engine have broken cranks under extreme use.  The option of radiusing the counterweight edges seems a safe bet.  There is plenty of counterweight remaining for balancing and the crank strength is not compromised.

There are two counterbalancer shafts in these motors.  Can they be removed?  I asked Triumph Performance for their opinion on this and on the method of reducing windage.     
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« Reply #2242 on: November 30, 2015, 03:16:10 PM »

Would 'sump-vacuum' help?
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« Reply #2243 on: November 30, 2015, 07:16:36 PM »

bo, do cranks like this balance similar to/same as odd fire harley cranks?  i had the sportster's balanced at 60% ( total reciprocating weight x 60% plus total rotating weight equals total bob weight for spin balancing) to move the "balance" up the rpm range. i could have opted for a lower percentage moving balance higher into the rpm range but stayed w/ the tried and true 60% and am good to 8000 rpm w/ the motor.  we talked about windage trays and/or and smoothing/fairing the 360 degree flywheels but opted to just use the factory scrapers and called it good.  in lieu of modifying  the crank, can you look at a windage tray or scrapers?
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wobblywalrus
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« Reply #2244 on: November 30, 2015, 10:07:58 PM »

The 270 degree crank makes these Triumphs run really smooth and they get better traction.  It is not in the bike now.  The old style 360 degree crank is in it.  The guy at Revco Precision in California balanced the crank when I put in the heavier pistons.  The balance factor was over 50 percent.  I do not remember the exact number.  It seemed to be too low.  The bike runs real smooth.  He knows what he is doing.

The oil is in a sump below the crank and the crankcase casting has a windage tray built in.  The counterweights just dip into the oil on the windage tray about a quarter inch when the motor is not running.  The oil pump sucks that up when the engine runs so the crank is spinning above the oil level.  The balancer shafts are about five inches above the oil level.  The engine is like a dry sump motor when running.  The crank and the balancers spin in the air.  I looked at using an oil scraper.  The pork chop crank lobes are away from the scraper more than half of the time.  I am not sure if it will work.

There is a fellow in Australia that races one of these and of course, there are the folks at Triumph Performance in Lomita.  I e-mailed both of them and asked if the counter balance shafts can be removed to get more power without creating a lot of vibes.  That, and radiusing the leading and trailing edges of the crankshaft lobes, might give me more horses without weakening the crank.

There is an extra breather on the crankcase to reduce internal pressure.  A slight vacuum in the crankcase might help.  I could hook the extra breather up to a suction pump.  Is anyone familiar with one of these setups for a bike?     
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Koncretekid
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« Reply #2245 on: December 01, 2015, 07:22:42 AM »

Counterweights dip 1/4" into the oil when the motor is not running, but not when the motor is running?  Where does it go in a wet sump motor? It surely doesn't drain that much oil from closed passages within the crank, etc. or your motor would be starting without oil where it's needed. If the counterweights are above the oil, I can't see how trimming them can have much effect unless they can be made to sling off the surface oil more effectively.

Additional breather on your motor? So you've got almost 1000cc of air pumping back and forth thru your breathers like an air compressor.  Connect all your breathers up to a reed valve breather and stop the pumping losses!

Remove the counter balance shafts?  You'll have to have the motor rebalanced, I would think.  From a conservation of energy principal, there would be no hp lost at steady state as those shafts aren't doing any work.  There would be some mechanical loss from the chain or gear drive and bearings.  From an acceleration standpoint, I would think they would be the same as a heavier flywheel so from a drag racing and road racing point of view, they could be detrimental.  On a long track like Bonneville, I don't think a lighter rotating mass would make much difference.  But now we have to look at 1 mile tracks; so maybe an advantage to take them out to gain that last bit of acceleration.

Tom  
« Last Edit: December 01, 2015, 07:40:12 AM by Koncretekid » Logged

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Stainless1
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« Reply #2246 on: December 01, 2015, 06:51:59 PM »

The balance shaft it to quite the motor harmonics around idle... look at the book for the adjustment... we pull them from suzuki bike motors all the time.  The gear drive and drag of the balancer uses HP just like transmission gear drag.  
It's a race bike, who cares if it buzzes the bars a little at low rpm.

added...
Tom, if your motor has a sight glass, look at it while the bike is running... oh no... all the oil disappears with the motor running.... wonder where it goes...
« Last Edit: December 01, 2015, 06:55:06 PM by Stainless1 » Logged

Stainless
Red Hat 228.039, 2001, 65ci, MSA Bockscar Lakester with a little N20 
MSA Bockscar Lakester #1000 my fastest mile 245 and change, 84 ci turbobusa motor... but Corey's 233 MPH H/BFL record is still 3MPH faster than mine.
wobblywalrus
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« Reply #2247 on: December 01, 2015, 10:09:44 PM »

The new Bonnevilles are air/oil cooled and the oil level drops when the engine is running.  The lube is all around the engine doing various tasks.  There is a sight glass on the side of the motor to observe the level drop.

The expert opinions I got cross the entire spectrum of experience and recommendation on crank and balancer mods, from "shape the counterweights like airfoils and remove the balancers" to "leave the balancers in and do not change the crank lobe shape for a 995cc engine."  These are condensed recommendations and not exact quotes.  All are from successful racers using these motors.

Yesterday I was dodging frost patches on the road in the predawn dark while I rode to work on the other Triumph.  Logic says I had better fix the salt damage on my truck so I can stay alive until spring and be able to tow the bike to Bonneville in the summer.  A couple of extra horsepower won't do me much good if I am dead or cannot drive to Utah.  I will leave the crank alone, the balancer shafts will remain in place, and I will concentrate on fixing my truck.  It was an easy decision.  All of my engines have names.  This low budget special will be the Ghetto Blaster.       
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Koncretekid
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« Reply #2248 on: December 02, 2015, 06:18:40 AM »

Stainless,
I have a dry sump motor and no sight glass.  I just thought it interesting that Triumph would design a motor in which the oil level at start-up would be high enough to ensure that the counterweights would spread all the excess oil around leaving no chance to completely eliminate the windage problem. Briggs and Stratton did that for years and the motors didn't last too long in my lawn mowers!  Controlled oiling would seem better than a splash system.  A deeper sump might be a good idea.

I've never had a bike with balance shafts and I agree that we don't need to worry about the out-of-balance buzzing for 5 miles at a time.  I would remove them, but Bo has already had his motor re-balanced with them in place, so removing them would require a another re-balance wouldn't it?

Tom
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wobblywalrus
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« Reply #2249 on: December 02, 2015, 09:24:35 PM »

Today I got opinion from a couple of more experts in this.  The counterbalancers in these engines provide secondary balance.  Fiddling around with counterweights only affects primary balance.  The secondary imbalance that comes with removing the counterweights might be a problem or not, depending on how the engine is mounted in the frame and the vibrational harmonics of the various parts of the bikes.  Removing the counterbalancers has caused problems.

The primary balance is the counterweights.  Their weight can be adjusted to provide good primary balance at high rpm.  A problem with shaving the balancer weights is to provide primary balance.  The counterweights can be drilled and heavy metal plugs interference fit into the holes.  The crank could be lightened by drilling around the web near where the big end is.  The pistons and rods could be lightened to get primary balance.

I looked at doing these things after work today.  The heavy metal inserts will require drilling the counterweights.  There is not a lot of room for this.  It will be hard to get significant added weight from heavy metal plugs to compensate for metal removal from the counterweights.  Drilling balance holes on the crankpin side of the crank weights will weaken them in a critical area.  I am not sure how to lighten the rods and pistons.

The bike is raced in FIM and the return run needs to be made within an hour.  Once I make the down run I wait for the FIM escort to accompany me back to the impound.  Then I go to impound.  Adding fuel or fixing things is done there.  Any adjustments in impound require me to walk down pit row to the truck, dig out what I need, walk back to impound, fix or adjust, walk back to the truck to put stuff away, and walk back to impound.  Then I find the escort, tell him to hurry up, and then we ride down to the other end of the course.  Next, I convince the flagger of the urgency of the situation.   Almost always, a few minutes before the hour is gone, they flag me off.  A smooth running bike that does not vibrate stuff loose is a real asset for an FIM racer.  Although I do not have time to monkey with the crank, I would not fiddle with it if I did have the time.  It is sort of like a sprint tuned engine vs a motor set up for endurance.  A person needs to finish to win.         
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