Fun with weights and math

[My427stang]

I posted this in two separate posts in the FE Forum, but I thought you guys would get a kick out of it.

I am getting ready to put together a 445 and running through some numbers. I thought it would be neat to show the difference in weights of the different combos, especially compared to stock and spell out where they differ.

Reciprocating weight - Piston, pin, locks, small end, rings, a little oil

- 489 FE, Diamond Pistons, 6.70 H beam rods, 7/16 cap screw - 985 grams
- 445 FE, Probe Pistons, 6.70 I beam rods, 7/16 cap screw - 877 grams
- 418 FE, cast Badgers, 6.49 stock rods, 3/8 bolt - 1129 grams (HEAVY, thats over 1/2 lb difference for each piston/rod small end combo)

Rotating weight - Rod big end, rod bearing

- 489 FE - 621 grams
- 445 FE - 602 grams
- 418 FE - 592 grams

How that translated to bob weights, keep in mind everyone has a little different technique based on a lot of hunch and attempts to counter expected harmonics, so numbers can vary based on a guy's favorite math.

- 489 FE - 2232 grams
- 445 FE - 2082 grams
- 418 FE - 2313 grams

It's neat to see that the aftermarket stuff is only slightly heavier at the crank, but can be 100s of grams lighter in reciprocating weight. that's a good thing. Significantly stronger parts, marginally heavier at the crank, but lighter out where it is changing direction, and by a significant amount.

Add to it a smaller rod bearing to boot and save on rod bearing friction and oil requirements, and a lighter crank pin. All good stuff

But when you add it up is when it shows how much different

4.25 SCAT crank weight 64 lbs...3.78 stock 390 iron crank 68 lbs

SCAT I beam rod big end weight total...... .17 lbs less than stock Ford 3/8 rod

SCAT/Probe recip weight total....4.4 lbs less than stock Ford cast


Summary

SCAT 445 cast crank w/ I beam rods and Probe pistons

4.17 lbs less rotating weight than a stock 390
4.44 lbs less reciprocating weight than a stock 390

Thats POUNDS, pretty big difference!

[65er]

got any pics? I've only seen the stock photos of those stroker kits, would love to see the actual stuff in some detail.

[My427stang]

I buy individual pieces, not a kit, but here are some old pics of the 489, its a Diamond piston / H-beam combo.   I'll snap some of the current build soon, its a Probe / I beam combo.  The crank is the same in both, but I have pics of neither, more to come

Here are a set of .047 over Diamonds as delivered




I do a little shaping to all of mine, especially if its going to be a pump gas motor, knocked the edges off, cleaned up some areas I think will get hot, I also don't particularly like a polished surface.  The first pic is partially done, compared to as delivered, the second is complete.  minor changes, peace of mind more than anything




SCAT H-beams, out of the box, then deburred, balanced and paired up by width (again a little anal they were at most .001 difference after deburring and equal in weight, but no harm to pair them up to keep clearances the same)




Short block - Used a Damper Dudes rebuilt balancer.  Balanced nicely and smack on at zero


Next day with the God-forsaken Crane rockers.....long gone and good riddance. 

[jayb]

I plugged your numbers into my inertia calculation spreadsheet to see how the variation in weight affects the torque required to accelerate the reciprocating assembly at various acceleration rates.  I made a few guesses because the inputs to my spreadsheet are total weight of the connecting rod, total weight of the piston, etc., so I had to make a guess on that using your bobweight numbers.  The calculations include the harmonic balancer and a 16 pound aluminum flywheel.  But anyway, here are the results:

418 FE:

1000 RPM/sec:  33.88 lb-ft
600 RPM/sec:  20.32 lb-ft
300 RPM/sec:  10.16 lb-ft


445 FE:

1000 RPM/sec:  30.9 lb-ft
600 RPM/sec:  18.54 lb-ft
300 RPM/sec:  9.27 lb-ft


482 FE:

1000 RPM/sec: 33.37  lb-ft
600 RPM/sec: 20.02  lb-ft
300 RPM/sec: 10.01  lb-ft

The lighter weights of the aftermarket components are partially offset by the longer stroke of the crank, which adds to the moment of inertia.  However, both stroker combinations still require less torque to accelerate than the stockish 390 setup.  Cool...

[My427stang]

Neat stuff!

[65er]

Very nice!  Took me a minute to figure out that the dots on the piston in the second pic were from the pegboard reflection. lol.

Do you know the actual weights of the pistons and rods?  Got me curious of how mine compare as far as just throwin' parts on the gram scale.

[My427stang]

489
Piston 518
Pin 157
Locks 4
Small end 246
Oil 7
Rings 53

Big end Rod 568
Rod bearing 53

418
Piston 655
Pin 140
Locks 3
Small end 260
Oil 7
Rings 65

Rod big end 540
Bearing 52

445
Piston 433
Pin 145
Locks 4
Small end 240
Oil 7
Rings 52

Rod big end 550
Bearing 51

All in grams, everything measured except 445 piston and pin, waiting for delivery.  I used advertised numbers, I will verify Friday when they show up

[e philpott]

Ross , did you see the titanium rods for sale on FE ?? .... I wonder how much the titanium would change the math

[My427stang]

I bet its 200 grams per rod, which would drop the bobweight by at least that much depending which end of the rod was lighter

Cool stuff