Milwaukee Midget

[Milwaukee Midget]

Do you have a 4.22 and 4.55 diff's.?

4.22's are what's in the car at the moment, and I misspoke earlier - 3.90’s are in the garage.  I think I've also got a really rare 3.70 set around somewhere.  I thought about 4:55's and grafting an MGB OD unit, but I suspect I'd be chasing my tail.

There are also some Datsun and Ford 5 speeds that could be made to work, but I suspect I'd have a tough time pulling an OD.

Taller tires are possible, but I'm pretty close to the limit at 22" on 15" wheels.

Park, did you get my PM?

Chris

[Speed Limit 1000]

Is it too late to protest?  Did they make 500 of them A-barths?  Can you put double bumps on yer roofs?  Does that mean a Fiat ran two days in a row (I forgot about the four hours of fix-it time)?

Pete still has Ben Jordan's Zagato, Stainless and I hope to help him get that record back. Over 600 Zagatos were built.

[fordboy628]

Midget,

I need some info for the valve train analysis.   Average component weights (accurate to tenths of a gram or hundredths of an oz.) needed for:

Tappets
Pushrods
Rocker arms

I am using a USPS Digital Postal scale for the other components & can weigh the above if you want to send or bring them down to the Dungeon.  Have located local wide format roll copier for the chevy/bmc adaptor plate drawing.

Almost finished with the "Dutchboy" gig.............
 
F/B

[Interested Observer]

Midget:    Some while back you had inquired about finding the rocker arm properties.  It looks like Fordboy is about to launch into an analysis and may have use for that information.  To further elaborate on the method for determining the moment of inertia, the attached diagram and practical advice is as follows:

The CG of the rocker can be determined by hanging it in different orientations from a string or thread and projecting the vertical lines of the threads to an intersection point, which would be the CG.  The distance from the CG to the center of rotation, “r”, can then be measured.

The bifilar pendulum is then constructed, with the rocker on its side (the axis of the rocker shaft would be vertical) and the two looped connections of the pendulum approximately equidistant from the CG.  The suspending filaments should be as light and flexible as possible--sewing thread is a good candidate.  The filaments need to be the same length and parallel to each other as well.  Having a long filament, h = about 36”, will keep the rate of oscillation slow enough to count comfortably.

The rocker is then slightly displaced in a rotational sense in the horizontal plane so that it rotates back and forth on the pendulum in the same manner as it does in service.  The frequency of the oscillation is then determined by timing the duration of a number of cycles--probably 20 to 40.

The information thus gathered is plugged into the following expression to determine the moment of inertia about the pivot point.
   Io = (Wa^2)/(4h(pi)^2 (fn)^2)  +  Wr^2/g

Example:
   W = 0.359 lbf
   a = 1 in.
   h = 32.5 in.
   fn = 20 cycles/37.7 sec. = 0.53 cps = 0.53 Hz.
   r = 0.3 in.
   g = 386 in/sec^2

      Io = 0.00108  lbf-in-sec^2

[Milwaukee Midget]

Fordboy, I can get you to the nearest gram –

Pushrod – 69

Rocker w/ adjuster 92

Tappets –

 

So I'll pull the vibration damper, the Gilmer drive and the cam cover, remove the cam, wipe the assembly lube off of the tappets, clean them with solvent, risk infuriating Kate further by getting caught weighing them on her kitchen scale –and she was none too happy with me weighing the pushrods and rockers, by the way - order up a new cam cover gasket, and then put it all back together again.

Or we could just accept that the fat lady already sang, and I can drop an e-mail to Anton and see if he knows what they weigh.

Interested Observer, you’ve just been promoted at Active Participant!  Thanks for the physics and geometry lessons. 

I’ll see if I can collect the data and replace the letters with numbers.

[fordboy628]

Midget,

DO NOT DISASSEMBLE THE ENGINE!!!

There is no need for the additional work/expense, as I can use the weights of representative samples that I have here.   Those numbers will be close enough to utilize for your "brain surgery".   If Dave can supply you with the actual weight of an APT tappet, THAT would be helpful, otherwise I'll use the weight from a new "Kent" tappet.

Normally I would want to have the "actual" weight of the components being used because that creates the greatest precision to the calculations & analysis.   BUT, since I'm going to add a 10%/15% margin of safety factor to the calculated spring tension required, we can be within 1%/1.5% of the actual weight and not screw this up too badly.   Just for yucks, what does a stock pushrod weigh?

Interested observer,

Thanks for digging out the formula & posting it up.   As Midget can attest, the Dungeon has a massive amount of records to sort through to discover bits of info relevant to this exercise.   Unfortunately, most of the stuff down there (including "frankenputer") has "survived" a Katrina-esque basement flood.........

The moment of inertia measuring set-up I created in the 80's used 6# monofilament fishing line for the filaments.   And I selected a "working" length of 36" for the filaments, go figure.......
 
Dutch/Fordboy

[Milwaukee Midget]

Fordboy -

According to Anton, the tappets are 43 grams.  Mine will be a smidgen lighter due to the re-radius Elgin put on them.

Stock pushrod - 53 grams

[Jack Gifford]

... I'm going to add a 10%/15% margin of safety factor to the calculated spring tension...

My [unpleasant] experience indicated that a true safety factor would add at least 40% to the calculated spring requirement. I'll wager that if you add 50% you'll be real close to what the cam lobe designer would recommend if you provide him with all the details. Just for chuckles, why not do that? The major cam companies are all more than happy to spend time discussing it with you.

[fordboy628]

... I'm going to add a 10%/15% margin of safety factor to the calculated spring tension...

My [unpleasant] experience indicated that a true safety factor would add at least 40% to the calculated spring requirement. I'll wager that if you add 50% you'll be real close to what the cam lobe designer would recommend if you provide him with all the details. Just for chuckles, why not do that? The major cam companies are all more than happy to spend time discussing it with you.

Jack,

I don't know what formula(s) you have been using to calcuate spring pressure requirements.   My experience is that I have never had to add 40%/50% to my calculated results to get an acceptable/workable consequence.   If I had to add as much margin as you suggest, I would conclude the formula(s) being used are less than useful........ OR, that the input values are corrupted.

I'll post up the formula(s) I've been using to Midget's build diary & you can do the same.   I suspect that there is a dramatic difference in the formula(s) being used.   Sorry you've had such a negative experience.

Cam designers/grinders can be a wealth of useful information.  Unfortunately, most major cam companies are uninterested in and/or have no experience with, the type of engines I'm usually working with.   And I'm the kind of guy who likes to double check things myself, especially if I'm writing the checks...............
 
Fordboy

[fordboy628]

Midget,

Full scale/size plan tracing of BMC engine plate to Chevy bellhousing adaptor on its' way to you via trusty USPS.   Copy also has some notes for other items required, such as water hose adaptors, etc.   Continueing to mine/dig for digital info for bolt hole location via "frankenputer".
 
'Doc' or maybe 'Sleepy', but probably 'Grumpy'.............

Quote from Obi Wan Lucas:  "These are not the dwarves we're looking for....................."

[fordboy628]

Midget,

Some useful information regarding gear ratios posted below.  Of particular interest are:

1/  RPM drops between shifts..........
2/  Max mph at redline (of 8500 rpm) in various gears...........



Once there is a torque curve/hpower curve to add to the equation, acceleration to various speeds can be plotted..................

Let me know if you want to propose any changes/explore any possibilities..............
 
F/B

[Milwaukee Midget]

Just for chuckles, why not do that? The major cam companies are all more than happy to spend time discussing it with you.

Jack, I’ve had my share of chuckles.  The chuckles start when you call a cam grinder to discuss something other than a small block Chevy.

We’re both dealing with orphaned engine designs.  What has your cam grinder been able to offer up, other than valve train generalities and off-the-shelf Mopar grinds for the 4 cylinder Poncho Hemi?

Yup, here come the chuckles again! 

Dema Elgin, on the other hand, has worked with Fordboy in the past, and he’s aware of what we’re up to.  An added bonus is that Elgin knows Spridgets pretty well – he’s built and raced them.  He's been extremely gracious with his time.
 
And as is often the case with engine development, pros often disagree.  We’re well above the spring recommendations that David Vizard puts forth in his book, “Tuning the A Series Engine” for an engine cammed similarly to mine.

Fordboy’s been in discussion with some folks who went higher than I have and have had problems with billet rockers breaking.  With the new radius on the tappets, and a better controlled break-in of the cam, I’m confident we’re about maximized.

[38flattie]

Just for chuckles, why not do that? The major cam companies are all more than happy to spend time discussing it with you.

  With the new radius on the tappets, and a better controlled break-in of the cam, I’m confident we’re about maximized.

Chris, I think the problem may be in your approach- You think you're about maximized. Do Like I do- take the point you think is maximum, add 10%, then proceeed as if you're still under max by 20%!

"Honey, I don't know why it broke!"  

[Dean Los Angeles]

Calculations, smalculations.

Tighten it until it strips, then back off a 1/4 turn.

Hey! I do use a calibrated torque wrench.


Run it till the valve floats, THEN you need a bigger spring.

On our Cyclops II, in consultation with Trebor Crunchog, we came up with the correct spring.
This is a photo of work in progress:

[Milwaukee Midget]

Well, I don't know if I could get 8 of them under the hood, but we could build something like this to overcome a slow launch -

http://www.youtube.com/watch?v=y0TDZlEeEqw