HarleyTechTalk

How much of an effect would 5.2 Grams have on a flywheel balance factor? The flywheels are balanced for 1302 and I have potentially 1297. I've been trying to achieve perfect balance for pistons AND flywheels. The wristpin I have was advertised incorrectly. When I recieved it it was 2.751 instead of 2.810 which is close to the original size of 2.818. So the 144gr wristpin that I ordered would be .065 shorter than the original  but at 144Gr it would balance out the front and rear pistons to less than .2 of a Gram. How important is that .065 of additional space for the Wrist pin? That would be .030 or so per side gap to the Circlip of retained by the Circlip. If it's super important then how important would the 5Gr be to balance of the flywheels? Was hoping to have perfect balance on both but I ordered based on what I thought I knew . So should I use the shorter wristpin for perfect balance or be off 5 grams on the flywheel balance? I hope that all makes sense. I'm terrible at conveyed communication in writing. Is using a slightly shorter Wristpin a issue? I had diamond cut me one thats 2.818 exactly like the original but it came out to 139GR leaving me unbalanced on the pistons by 2.2GR and 5gr on the flywheels.

I'd rather not have excessive side clearance.
Can the correct length wristpin be honed on the inside to remove the extra 2.2 grams? Get the weight you want, and the length you need?

All of this assumes the crankshaft has already been balanced to the weight of the piston assemblies used in the discussion.

If the crankshaft was built by Harley the odds are that it is not within whatever balance spec you think it is.

Instead of lightening the wrist pin, have you considered lightening the underside of the pistons?

That's going to have to be my next move. I didn't know how hard it would be to machine off the required material because of the hardness of the wristpin. I'll order 3 and see what works. That basically answered my biggest concern as I didn't feel like there should be any movement in the bore of the wristpin beyond the stretch from heat. Ive found 2.850 and 2.900 writpins that I'll snag up and see where it leads. Anyone know what or cutter or bit I will need for H13 on a lathe?

It's a brand new Darkhorse Mano-O-war.  I have but never have done it and didn't want to screw it up. The DH I ordered was balanced to 1302gr so I'm under by 7.7Gr with the S&S piston Set. I ordered a 144Gr wristpin that wasn't the correct length. The 144gr put my in the perfect balance perfect piston balance. So when I got the wristpin and seen it was 2.750 I've been trying to find a 2.818 wristpin that weighs 144Gr

Quote from: Wookie3011 on Today at 07:23:27 AMIt's a brand new Darkhorse Mano-O-war

This makes it even easier. You should have received a balance sheet with all of the weights on it. You can reverse the math with the new piston assembly weights and determine the new balance factor. I DH balanced it at 60% and the new piston assembly weights change it by x% then you have your answer. I suggest you get out your calculator and figure out the new balance factor.

This is a link to a post awhile back where we discussed balance and balance factor that turboprop is speaking of.

One thing that MAX says in the post is that a bagger or Dyna with isolation mounts would likely be 52% balance factor. And that solid mount is 60%. I assume that may not be ok for your 'Beta' motor. But I would research that to be sure.


https://harleytechtalk.com/htt/index.php/topic,117218.0.html

Thanks I've been reading thought it for a while. The perfect solution would be finding a 2.818 Wristpin that weighs 144Gr. That gives me perfect balance on the wheels and the pistons. This wrist pin would go on the front piston. I'll have diamond try again with a heavier material. If it's over that would even be fine as I could hone the inside.

Thanks

Does anyone know a formula to use that would identify how much material A certain wristpin could weigh if material was removed? Say I got a .927x2.950 .185 wall wristpin that weighs 163Gr. If i cut off X amount how much would it weigh in Grams?

Below is how I get the area of the pin less the bored area, and give the cubic inch per gram.

I'm also not 100% sure about how much you wanted to remove, you kind of jumped around a little. I believe what you said was a total of 5.2gr needs to come off.

Your Data
OD of pin .927 / 2 = .4635 radius
ID of pin .557 / 2 = .2785 radius
length = 2.950
weight = 163gr

outside area including the center area of the pin
PI*.4635^2*2.95=1.9910004841447892824384628459838  (use 1.9910)

inside area (already removed)
PI*.2785^2*2.95=.71882353464789007479935002717657  (use .7188)

pin area less the bore = 1.9910 - .7188 = 1.2722 cu in

1.2722 cu in / 163gr = .0078 cu in

.0078 cu in = 1gr

.0078 cu in x 5.2gr = .04056 cu in of material


inside area to bore
PI*.286250^2*2.95=.759386035 (use .7593)

.7593 cu in - .7188 cu in = .04050 cu in to remove


current ID = .557
new ID = .5725
.5725 - .557 = 0.0155
amount to bore 0.0155


And get a nice electric scale that measures in grams to check your work as you go. Start with something like 0.005 x length.


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I also would consider what turboprop said, look into removing some material from the underside of the piston. It would be easier since they're aluminum.

"The DH I ordered was balanced to 1302gr so I'm under by 7.7Gr with the S&S piston"

Why didn't you send the pistons, rings, wrist pins etc., to Darkhorse with your flywheel assembly? 

The original wrist pin was 133.2Gr I ordered a 144gr wrist pin which I was going to hone to the desired weight  the listing had a "Typo" on the length. So I ordered the flywheels with this equation in the false hope that I had secured the wristpin I needed. It was a bad choice on my end. I should have waited to recieve it. I'm using a OHAUS Dial-O-Gram 2610g that is accurate to the tenth of a gram. Ill get there but im going to need some ductape for my brain after crunching the provided equation. Time to go brush up my math skills. I didn't know you could send them your pistons and they would match them.  Thanks Brian

What symbol or calc is this Brian^

Quote from: Wookie3011 on Today at 08:42:17 PMWhat symbol or calc is this Brian^

raised to the power of
in this case it's 2
or said another way ... squared

Thank you