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Author Topic: New Vintage Project, 250cc M-VG, Reconstruction of a 1933 French Jonghi 350  (Read 27699 times)

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Offline thefrenchowl

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Hi, Koncrete Kid,

Data was put in Excel file... 1st two rows for titles so it really starts at row 3, so data rows 3 to xxx

1st column A was degrees, B exhaust and C inlet

For some reason, it's open web excel..., I can't get the horizontal axis to read the 1st column A, it only wants to read the row number...

This is the timing for both race and street cams:

Race cams:
Lift: .334
came TT 2, exhaust:
opens 77 deg. before BDC
closes 38 deg. after TDC
Duration 295 deg.

came TT 6, inlet:
opens 46 deg. before TDC
closes 60 deg. after BDC
Duration 286 deg.

Overlap 38 + 46 = 84 deg.

Street cams:
Lift .321
came 114, exhaust:
opens 63 deg. before BDC
closes 22 deg. after TDC
Duration 265 deg.

came 114, inlet:
opens 20 deg. before TDC
closes 47 deg. after BDC
Duration 247 deg.

Overlap 20 + 22 = 42 deg.

Measured with following valve lash: 4 thou inlet,  6 thou exhaust.

Running clearances will be more like 6 and 10 thou.

Patrick

« Last Edit: April 06, 2019, 12:29:55 PM by thefrenchowl »
Flat Head Forever

...What exactly are we trying to do here?...

Offline Koncretekid

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I had similar problems using MS excel, but somehow got the x axis to post in degrees.  I'll try to post one here.  The Megacycle X4 cam that I use is 33 - 69 inlet and 69-33 exhaust, but measured at .040".  So when I degree my cams at every 10ยบ as you have done, I always make sure to get a degree reading at .040" opening and closing in order to compare with other cams.

The following example is a comparison of a Megacycle X4 cam with a Sifton HT.
« Last Edit: April 06, 2019, 06:54:34 PM by Koncretekid »
We get too soon oldt, and too late schmart!
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Offline thefrenchowl

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Hi Koncrete Kid, thanks for sharing your cam data.

I sort of agree with you about the 40 thou reading to compare with other cams, but...

Since for a given lift most cams have roughly the same rising ramp above the 40 thou lift, the interesting bit of each cam design is how much time/degrees it spend either getting to 40 thou or closing from 40 thou.

The Sifton on your graph shows much less time/degrees spent there.

So on paper, it might look like a softer cam than the other just looking at the degrees while in fact it's a fiercer and faster accelerating cam off the follower... which should be harder on the components as well...

On another forum, someone posted a compare graph of an alloy XR cam versus a KR cam... Well, the XR did use 50 degrees more on each side to get where the KR cam was at 40 thou lift.

Obviously, it allows faster revs than on the KR with softer openings/closing, but in me eyes, it's 100 degrees lost that cannot be recovered!!!

Patrick
Flat Head Forever

...What exactly are we trying to do here?...

Offline fordboy628

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Patrick, Tom,

JMHO, but I analyse a lot of valve train motion.   Depending on what you want to do, you might want to add more data to your testing regimen.   Obviously, accuracy of measurement, has a HUGE impact on the results, especially the derivatives.

Even if all you care about in your cam analysis is displacement, 10 degree interval increments at the crank is too "coarse" IMO.   As Patrick stated, the measurement interval is so great that "unintended smoothing" of the data occurs, giving a false impression of the actual motion.   And if you intend to make any assessment of derivatives, (velocity, acceleration and jerk), coarse data accumulation by hand will not give you anything but error filled data.    To make "good" data driven decisions, well, the data has to be "good" to start with.   :wink:

Things you can easily do, that will be helpful and give you better data:

1/   The best situation would be to have your cams "profiled" on a dedicated fixture such as a Cam Doctor, Cam Professional or Cam Analyst.   This can be inconvenient and expensive, but gets you the best data available at the "non-manufacturer" level.

      If you still want to accumulate data by hand, you can improve your accuracy by:

A/   Decrease the measurement "interval".    Every 5 crank degrees or better yet, 4 crank degrees is better than every 10 degrees.
2/   Increase the diameter of the degree wheel.    This lengthens the arc segment per degree, thereby adding accuracy.     A 16" diameter degree wheel is twice as accurate as an 8" wheel . . . . .
d/   Use an electronic indicator that reads in .0005" increments.      .0002" or .0001" is better still.    One with enough travel could be pricey.

These changes would give you "useable" data for velocity, probably for acceleration, probably not for jerk.



I no longer try to graph or analyse cam data in Excel.    It is just too difficult to finesse the software to do what I want, as you both mentioned.    I use cam specific software which is excellent and expensive, BUT, you can use a freeware program called  DatPlot by Michael Vogt.   It allows a second y axis, labeling freedom, and other controls that are tedious in Excel.    Here is a link to some sample graphs.

https://vintageracing.online/threads/racing-engines-a-technical-examination.1092/post-11154

Data entry in DatPlot can be more time consuming, there is no manual, etc.    But, WTH, FREE!

Also, you want to take a hard look at things like lash ramps, transitional velocities, and seating velocity.    These items can all vary based on the ACTUAL lash.

Most cams have the same "rising ramp" because for a given tappet diameter there is a maximum velocity per degree that can be used before the cam runs off the edge of the tappet.

Sent you both a PM

 :cheers:  :dhorse:  :cheers:
Fordboy
« Last Edit: April 07, 2019, 08:01:23 AM by fordboy628 »
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Offline thefrenchowl

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Thanks for your advice, Fordboy,

I do not have the money to develop new cams for this 1933 engine, so basically I am stuck with what I have in hand, ie race cams with some wear, flat shoe type tappets with some wear and drive gears with more lash than I expected!!!

I can't do much with the cams or the gears...

I did smooth a touch with a stone the worst of the flat shoes wear, but these are all hardened by carburizing, about 20 thou deep, so I can't dig too much in!!!

The recording of the timing was mostly to quench my curiosity and compare the race cam with the street cam since I have both variants of this bike.

My degree wheel is 9"1/2 (not too shabby then!) but any bigger wheel means I'll have to fit the pointer on the head!!!

See you around,

Patrick
Flat Head Forever

...What exactly are we trying to do here?...

Offline thefrenchowl

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Hi,

Engine finished today!!!!!!!!!!!

PO had put a 1943 one franc coin on the primary check plug opening, I left it...



Cam timing:



Engine in frame plus some safety wiring...



Piston:





No head gasket, high temp paint in place:





Compressing the magneto felt gasket!!!!!!!!!!!!!



Spark timing, 36 degrees before TDC:



Finished product...



So long,

Patrick
Flat Head Forever

...What exactly are we trying to do here?...

Offline thefrenchowl

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 :-D

Exhaust pipe and kicker...



Patrick
Flat Head Forever

...What exactly are we trying to do here?...

Offline Koncretekid

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If possible, I would try to get a machine shop to broach several extra keyways in your crank pinion (assuming you have a keyed pinion) so that you could try retarding the valve timing, unless that would upset your ignition timing.  Of course, you won't really know if it would help without some dyno time, but it has worked for me.
Tom

P.S. And yes, Fordboy, having more accurate data could lead to more knowledge, but do I really know what to do with that knowledge?  I'm quite happy to know what the terms mean, how they affect the performance of my motor, and allow me to make some minor changes to go faster!
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!

Offline thefrenchowl

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Hi,

Just poped at the painter to check progress or lack of it... Well, it was all done!

So, well filled afternoon!!!











 :-D Patrick
Flat Head Forever

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Offline salt27

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She's Gorgeous! 
Well done Patrick.   :cheers:

Online Peter Jack

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Good job Patrick!!!  :cheers: :cheers: :cheers:

Pete

Offline Doc B.

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Beautiful! Thanks so much for sharing the build.

Offline sabat

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Beautiful job!    :cheers: :cheers:

Offline Harold Bettes

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Patrick,

You've done well. Hope it runs as well as a package as you have done your part.

Regards,
HB2 :-)
If it was easy, everybody would be doing it.

As iron sharpens iron, one man sharpens another.

Offline Koncretekid

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Beautiful job, Patrick,

Are you sure you want to put that on the Salt? 

Tom
We get too soon oldt, and too late schmart!
Life's uncertain - eat dessert first!