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Author Topic: Twin Engine Panther from England  (Read 57483 times)
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SUMO
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« Reply #195 on: March 28, 2012, 07:58:06 AM »

yea there are 2 cam followers in there, they are just sitting on the shaft so level with each other

theres not an awful lot of spare material on there to remove really that doesnt add strength to them

as for doing everything at once - not by far, theres a ton of stuff i want to do if this works. done the big things. but if i didnt do a chunk at once it would take years and years to get through all the mods. panther tuning isnt a documented practice, very few idiots start with a panther motor to go fast, i havent done anything too radical yet so with a little luck and a fair breeze i'll be fine. if not it goes bang and i see what failed and dont do that again

yes they are ali rods but im pretty confident they will be are ok they are pretty big dia and very heavy wall [but who knows] if need be i can make some steel ones if i have issues

as a point of interest / amusement i set up my digital tach on my standard solo panther last weekend - it idles at 450 rpm, tops at about 5000 ish  grin - im looking at maybe 6000 rev limit i think on my tuned motor. i'll see when it feels to be shaking itself it bits and back off a bit
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panic
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« Reply #196 on: March 28, 2012, 10:43:04 AM »

Alum pushrods only about 1/3 as stiff as steel, no weight is saved. When they're really long, a press-fit sleeve over the middle 25% helps.
The rockers can definitely stand some weight loss. Keep the depth (top to bottom) but narrowing the tip helps.
A flat tip increases the rate. A larger convex radius will as well, but hard to be accurate with such a small surface. Strictly speaking, a concave radius is even faster but risks destruction due to side thrust.
You can also change the intake to exhaust bias somewhat by changing the radius on only 1 tip (like Triumph did) rather than change the cam, best info on whether this will help is by flowing the heads. As a guess: if the exhaust percentage is above 80% of intake, flatten the intake tip. If below 70% flatten the exhaust
The easiest safety margin to prevent catching an edge is to make the contact longer, although there is obviously a weight penalty.
« Last Edit: March 28, 2012, 10:44:57 AM by panic » Logged
panic
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« Reply #197 on: March 28, 2012, 10:45:37 AM »

What do the rockers in the head look like? What ratio?
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SUMO
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« Reply #198 on: March 28, 2012, 11:00:50 AM »

What do the rockers in the head look like? What ratio?
they look like this - no idea on ratio though


* Picture 1.png (116.55 KB, 630x539 - viewed 127 times.)
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panic
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« Reply #199 on: March 28, 2012, 11:31:42 AM »

Ratio looks small, if it's even positive (older designs frequently used 1:1 so as not to flatten the lobe).
I see oil grooves on the shafts - is there oil pressure to the rockers?
I suggest once you have the head ready to go that you assemble the rocker gear and do the usual mid-lift test. Since wear, lobe height etc. affect rocker geo, you'll need to know how close it is.
The combination of seat recession and increased lift require corrections in opposite directions, and tend to cancel each other out, or at least make the end result better than either individually.
The shaft height is fixed by the hole position in the stands, unless you make eccentric plugs to re-clock the shaft holes, or cut them off and make new ones. The stem height of course can easily be increased by lash caps.
Do you have any stem height above the collar area which can be trimmed if needed?
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wobblywalrus
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« Reply #200 on: March 29, 2012, 12:35:42 AM »

Sumo, one thing to do is put in your standard cam and followers.  Put a dial indicator on top of your valve spring keeper.  Measure valve travel vs degree of cam or crankshaft rotation.  Plot the data with the degrees on the x-axis and travel on the y-axis.  The valve travel curve rises and falls when the valve opens and closes.  You will be surprised sometimes.  The curve often will not be a smooth sine wave shape.

The curve shows valve position vs degrees,  The steepness of the line represents velocity.  The steeper the line, the faster the valve travels.  The rate of change in the curve steepness is valve acceleration.

Put in your modified cam with standard lifters and measure everything again.  Then try your standard cam with the modified lifters.  Then try the modified cams and lifters.  You want the setup that gets the job done with the smoothest increases and decreases in velocity and acceleration.

Force is related to mass and acceleration.  Pay the most attention to acceleration.  Anything significantly beyond the acceleration of the stock setup means racing springs are a good idea. 

In the past I have shown these curves to a spring specialist and brought my head and valve components with me.  They look at the curves, the rpm I want to use and they weigh the parts.  Then they match me up with some springs or make them.

This is a lesson I learned the hard way.  I did not pay attention to valve springs.  Valve float led to the head cracking off of the valve, dropping onto the piston, then the engine ate itself.  It was an engine I built for a customer.  That was worse than losing one of mine.   
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Tman
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« Reply #201 on: March 29, 2012, 02:51:27 PM »

Sumo, one thing to do is put in your standard cam and followers.  Put a dial indicator on top of your valve spring keeper.  Measure valve travel vs degree of cam or crankshaft rotation.  Plot the data with the degrees on the x-axis and travel on the y-axis.  The valve travel curve rises and falls when the valve opens and closes.  You will be surprised sometimes.  The curve often will not be a smooth sine wave shape.

The curve shows valve position vs degrees,  The steepness of the line represents velocity.  The steeper the line, the faster the valve travels.  The rate of change in the curve steepness is valve acceleration.

Put in your modified cam with standard lifters and measure everything again.  Then try your standard cam with the modified lifters.  Then try the modified cams and lifters.  You want the setup that gets the job done with the smoothest increases and decreases in velocity and acceleration.

Force is related to mass and acceleration.  Pay the most attention to acceleration.  Anything significantly beyond the acceleration of the stock setup means racing springs are a good idea. 

In the past I have shown these curves to a spring specialist and brought my head and valve components with me.  They look at the curves, the rpm I want to use and they weigh the parts.  Then they match me up with some springs or make them.

This is a lesson I learned the hard way.  I did not pay attention to valve springs.  Valve float led to the head cracking off of the valve, dropping onto the piston, then the engine ate itself.  It was an engine I built for a customer.  That was worse than losing one of mine.   

 I just learned more in your post than I have all week on the entire site! Thanks! cheers
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« Reply #202 on: March 29, 2012, 11:42:49 PM »

I think a plot of valve motion vs. crank rotation is going to have some weirdness in it due to follower arc travel, so don't expect a clean shape like the cam mfg. pretend to offer.
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wobblywalrus
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« Reply #203 on: April 01, 2012, 10:03:03 AM »

The magazine is Classic Bike Guide published in Horncastle, England, not far from Panther Territory.  www.classicbikeguide.com  My issue with the valve spring article was tossed out.  I cannot find it anywhere.  The Flintoft articles were published in the last 6 months.  They have a phone # to call for help with finding old articles.  All of them give good info to the home builder.   
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wobblywalrus
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« Reply #204 on: April 01, 2012, 01:08:37 PM »

While I was rooting around in a lifetime of hoarded junk for the spring article I found one of my old engineering textbooks "Graphics in Engineering Design" Third Edition, by Alexander Levens and William Chalk ISBN 0-471-01478-8

This is where I learned about the valve displacement-velocity-acceleration curves.  There is an example problem and the book discusses oscillating cam followers like yours, roller followers, flat tappets, and point followers.  The pole and ray graphical integration and differentiation methods are what I use.

This is a very good book and the methods learned from it have helped me throughout my career.  A lot of this stuff is a lost art.  A used copy would be well worth its purchase price.
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Old Scrambler
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« Reply #205 on: April 02, 2012, 12:17:38 PM »

Just bought a copy for $12.99 delivered.........thanks Wobbly
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SUMO
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« Reply #206 on: April 02, 2012, 02:33:28 PM »

SHE LIVES

started 4th kick from rebuild. this is after a spin round the block. but started first kick warm Smiley



first stage test motor done. need to test for a bit but so far so good.
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Geo
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« Reply #207 on: April 02, 2012, 02:52:51 PM »

Yahooo!  I don't think I ever had a bike that started that easily!  cheers

Probably what kicked me off the fence to the car side  grin

I'm ready for the next phase.  Looks good.  Don't just stand there get riding!

Geo
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SUMO
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« Reply #208 on: April 02, 2012, 03:01:44 PM »

cheers

get the timing right and a good strong leg works wonders on most bikes  grin
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« Reply #209 on: April 02, 2012, 03:12:18 PM »

Killer news!

Nothing like the first start-up - and even more so with British antiques - there's alway that niggling doubt . . .

I'll lift an Old Speckled Hen to you when I get home.  cheers  cheers  cheers
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