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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 521233 times)
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wobblywalrus
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« Reply #2910 on: October 29, 2017, 11:37:54 AM »

A cam was put in the lathe and I attempted to remove the welds.  Three different types of too bits could not cut the weld.  Then I got smart and deployed Mister Angle Grinder.  The weld was ground down quite a bit.  Then, I tapped the gear and the weld broke.  Heck, these welds might be brittle.  The cam was turned 180 degrees and the gear tapped without any grinding.  The weld broke.


* 2018 Build 004.JPG (126.08 KB, 762x600 - viewed 29 times.)

* 2018 Build 005.JPG (129.48 KB, 800x600 - viewed 36 times.)
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wobblywalrus
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« Reply #2911 on: October 29, 2017, 11:39:09 AM »

The gear was gently tapped down off of the cam.


* 2018 Build 006.JPG (110.37 KB, 750x600 - viewed 31 times.)
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wobblywalrus
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« Reply #2912 on: October 29, 2017, 01:24:05 PM »

There are two race cams I use.  One set is the older all purpose cams.  The other is the Bonneville race cams.  Adjustable cam gears were ordered for both.  The obvious measurements are checked.  The original gear inside diameter is measured.  The ID is 1.517.
A gear from a set of adjustables is checked.  The ID is in the 1.490's.  The fit is too tight.  They will be sent back to the supplier for a refund.  The IDs of the gears in the other set is checked.  They are 1.517.  This set will be used.  The old gear is used as a reference.  Otherwise, the tolerances would be checked using guidance in the Machinist Handbook.

The hot setup for these engines is to port and polish the head, use late model T-100 high compression pistons, put in early model 790 cams, and leave the rest alone, with standard air box, filter, and intake snorkel.  This makes a fast engine and avoids all of the funkiness of using non OEM parts.


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wobblywalrus
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« Reply #2913 on: October 29, 2017, 01:29:38 PM »

Heat is used for the gear reinstall.  The gear is heated with propane.  It is not hot enough to lose its temper.  The cam is slid into the gear.  The gear and cam are clamped in the arbor press until cool.  This is important to get a tight fit between the gear and the shoulder of the cam.


* 2018 Build 010.JPG (185.55 KB, 964x768 - viewed 20 times.)

* 2018 Build 011.JPG (172.76 KB, 860x768 - viewed 25 times.)
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wobblywalrus
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« Reply #2914 on: October 29, 2017, 03:41:10 PM »

There is a slight radius at this location on the gear holder.  The inner edge of the gear is sharp.  There is interference and the gear is held .010 off of the holder.  Should I put a small radius on the inside face of the gear so it fits up against the holder flange with no clearance?


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* 2018 build 014.JPG (130.37 KB, 700x600 - viewed 17 times.)
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fordboy628
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« Reply #2915 on: October 29, 2017, 05:02:26 PM »

There is a slight radius at this location on the gear holder.  The inner edge of the gear is sharp.  There is interference and the gear is held .010 off of the holder.  Should I put a small radius on the inside face of the gear so it fits up against the holder flange with no clearance?

Definitely

 cheers
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« Reply #2916 on: October 29, 2017, 06:54:09 PM »

Thanks.  Will do.

One experience type lesson I learned we as about welding rings onto shafts.  The weld can heat the ring so there is a clearance fit.  The ring hardly ever settles back down to where it should be when it contracts during cooling.  Now the rings are restrained so they move back into place where they should be.  This should not be a problem with these small tacks.  I am not taking any chances.
 
The old all-purpose cams were checked for valve opening degree settings when they were installed.  They were OK.  It was almost impossible to get decent power from that engine during the next six or seven years.  No matter what I did, power was never over 87 at the back wheel.  The cam gears were slipping on their shafts and the valve timing saw goofus.  Now, the gears are tacked to the cams now so they will not move.


* 2018 Build 015.JPG (105.3 KB, 800x597 - viewed 22 times.)

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wobblywalrus
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« Reply #2917 on: October 29, 2017, 06:59:40 PM »

The squirrels are bringing in nuts and leaving them all over the machine tools and welding bench.  Winter is coming.

The cams are checked to make sure they are still straight.  I do this with new cams and old ones that have been worked on.  Another experience taught lesson.  My typing finger is out of breath.  It is time for Sunday steak dinner at the local pub.


* 2018 Build 017.JPG (118.56 KB, 800x600 - viewed 26 times.)

* 2018 Build 018.JPG (131.91 KB, 800x600 - viewed 33 times.)
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wobblywalrus
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« Reply #2918 on: October 31, 2017, 09:02:11 AM »

The cams are symmetrical with lobe centers halfway between the ramps and the same profiles on either side.  The digitized profiles are in the "D" program along with measured flow data.

Cam chains wear and cam timing retards with use.  An estimated four degrees retard in crank degrees is anticipated.  Lobe separation angles of 108, 110, and 112 were looked at in the program with 4 degrees advance when the new cam chain is installed, two degrees advance at midpoint in the wear cycle, and no advance at chain replacement.

The combos with 108 LSA are 104-112 initially, 106-110 at midlife, and 108-108 at replacement.  This gives good torque and power throughout the chain life.

The settings using 110 LSA are 106-114, 108-112, and 110-110.  These also give good performance and it is identical to the 108 LSA.

The 112 LSA uses 108-116, 110-114, and 112-112.  Power and torque are not as high as with the other two LSA.

Some new high compression pistons will be made.  It seems the 110 LSA will keep the valve heads further from the crowns than the 108 LSA and this will allow shallower valve pockets and more compression.  Does this make sense?  It was figured out at midnight and hopefully the logic is sane.
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« Reply #2919 on: October 31, 2017, 10:26:24 AM »

Makes perfect sense.

I don't know what static compression you are aiming for but, with the size of valves you are using, along with the race cams;  I would suspect that 106 on the intake maybe a tad too close with the PTV clearance.  Likewise, you may run into issues on the exhaust PTV about the 109 mark.  108/112 maybe the winner.
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« Reply #2920 on: October 31, 2017, 11:32:32 AM »


It seems the 110 LSA will keep the valve heads further from the crowns than the 108 LSA and this will allow shallower valve pockets and more compression.  Does this make sense?  It was figured out at midnight and hopefully the logic is sane.


Yes.   You are doing fine, but I DO NOT recommend doing critical analysis when you are sleep deprived.    Sleep deprivation does nothing positive for anyone.

How it works is:  With equal timing and the center at TDC, the "tighter" the LCA, the LESS valve to piston clearance that you have.  "Opening up" the LCA retards the intake for more clearance, AND, advances the exhaust for more clearance.   As you can see, it can get "tricky" quickly, when the timing is not equal to TDC.

2 degrees of cam change gains or loses valve to piston clearance depending on which direction you go.  The rate per degree is equal to the net valve lift (or loss) per degree at that point on the flank lift curve.   The maximum flank lift per degree is fixed by tappet diameter for "flat" tappet cams.   This can be a significant amount, so you need to do a check at the mock up stage, OR, do a VERY accurate simulation.

On some engines, you also need to check on valve to valve clearance.   On big valve Cosworth 4v engines, advancing the inlet cam REQUIRES advancing the exhaust cam just to maintain valve to valve clearance.   It's not the best for power, but it is necessary to keep from "clashing the valves".

Most engines may run better with the cam(s) 2 to 4 degrees advanced.    Larger trapped volume from the early intake closing helps provide more torque, with little to no top end bhp penalty.    BUT, when you get closer to the "optimum cam profile for the application", cam timing becomes "very fussy".    "Long duration" cam grinds seem to benefit from this strategy more than "high intensity" cam grinds.   Again, it is about the "trapping volume".

Where the closest point of valve to piston clearance is located, depends primarily on cam positioning (timing), BUT, Build Geometry (tm) does have influence on this critical performance parameter.   Build Geometries which feature long piston dwell times at TDC can create fitment difficulties.    It's the old: "Five pounds of crap in a three pound bag" problem.

And, achieving a suitably high compression ratio is ALWAYS a "dogfight" with small displacement engines, regardless of whether they are big valve or small valve.   It's never a problem on a 632 cubic inch BBC, but it's always difficult below 122 cubic inches . . . . .   undecided

BTW, IMHO, if your engine runs better with the cam(s) more than 4 degrees from what is recommended, you need a different cam or cams, or possibly: "more development".

Hope this helped . . . . . .
 cheers
« Last Edit: October 31, 2017, 11:39:54 AM by fordboy628 » Logged

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« Reply #2921 on: October 31, 2017, 09:38:06 PM »

The most advanced setting is when the cam chain is new.  That is 106-114.  The intake valve to piston clearance will be checked with the intake cam at 106.  Clearance is smallest then and it gets greater when the cam chain wears and the cams retard.

The 108-112 setting is midway in the wear cycle.

The most retarded setting is when the chain is worn and the cams retard to 110-110.  The crown to exhaust valve head clearance will be checked at that setting.

Arias made the pistons in the bike.  The plan is to measure the clearances with those pistons and send them to Arias with the piston order.  It will be best to raise compression by reducing valve pocket size is my best guess.  Raising the dome might screw up the turbulence patterns.  The pockets are way too big now.

Hopefully my logic is OK and I do not have any concepts backwards.  Thanks for all of the advice.  It helps. 

 
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« Reply #2922 on: November 01, 2017, 07:56:57 AM »

Last night I did some book learning and computer modeling.  Vizard has a graph that uses valve diameter to displacement ratio to get LSA.  It gives an LSA of 107 when his compression ratio correction is applied.  The "D" program has a cam timing optimization feature.  It recommended ten combinations in the 107 to 108 range.  The concept of lost and non-recoverable compression on good breathing four valve engines, rod stroke ratio, and compression ratio is also explained.

It looks like it is more critical to not have too wide of an LSA in these engines as compared to two valvers.  Tonight I am going to model LSA's of 107, 108, 109, and 110 with advance leads of 4, 2, and 0 degrees.  The "D" program gives me trapped mass numbers.  The LSA combo that maximizes those will be noted.

Is there something else I need to look for in addition to trapped mass and checking the valve to piston clearances?   
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wobblywalrus
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« Reply #2923 on: November 02, 2017, 08:45:52 AM »

Trapped mass is at crank position TDC is tabulated for 500 rpm increments from 5000 rpm to 9000 rpm.  LSA angles of 107, 108, 109 and 110 are tabulated a 4 degrees advanced, 2 degrees advanced, and no advance.

The 7,000 to 8,000 rpm trapped mass is almost unaffected by LSA angle or advance changes.  Trapped mass below 7,000 rpm benefits from tighter LSA angles and more advance.  The opposite occurs above 8,000 rpm.

This was done at SAE atmosphere.  Tonight it will be redone using Bonneville air.   
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« Reply #2924 on: November 02, 2017, 09:11:21 PM »

The worksheet from last night


* 2018 Build 019.png (453.78 KB, 741x1024 - viewed 33 times.)
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