Ultra-light pistons

Hey,

I finally have a decent mass balance... so going to balance rods and pistons.

The high performance pistons I got for the Justy (in a cardboard box under the workbench marked "pistons from junked motors" do not have any balancing bosses.

I assume I can resort to my days of balancing outboard motor pistons and just drill the backs lightly near the centers?

Thanks!

What's the weight difference?

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

I would recomend cutting down the bottom of the skirts. I bet they are soooooper long. It's also a safer area then the backside of the dome, since, well, it get's really hot and a lot of pressure right above it.

But like John asks, what's the weight difference and/or how much do you have to remove?

What, real data? ?? are you kidding?

1. 235.85 g
2. 233.51
3. 233.71

wrist pins

1. 83.57
2. 83.49
3. 83.62

so even tweaking with the wrist pins I still need to lose 3 g from the one. I have another that is closer but has a bit slap damage. ..

oh yeah and edit. .. right skirts! I could lose friction area and gain massive HP right there!



Edited 1 time(s). Last edit at 06/18/2013 08:27PM by Mad Matt F.

Are you going to have your entire rotating assembly balanced?

Quote
Mad Matt F
What, real data? ?? are you kidding?

1. 235.85 g
2. 233.51
3. 233.71

wrist pins

1. 83.57
2. 83.49
3. 83.62

so even tweaking with the wrist pins I still need to lose 3 g from the one. I have another that is closer but has a bit slap damage. ..

oh yeah and edit. .. right skirts! I could lose friction area and gain massive HP right there!

I'm sorry, don't know what got into me asking for data, what a fool.

You know that to loose 3 full grams you gotta carve away about 1 cubic centimeter of aluminum, dontcha.. Where you gonna carve away that much material?

What do you 3 rods weigh?
SHIT I did it again! Sorry!
Don't put your rod weights up! DON'T!

I'm likely to slip up and suggest something like mix an match the pistons and rods a little and then say DONE cause you ain't revving this thing to 9000! What do you think will happen if you're out by 1-2 g?

So don't say what the rods --with bolts and nuts and bearings weigh!

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

1cc of aluminum is probably 0.050 from the bottom of the skirt. That's not much at all.

The whole story?

What? I don't understand the need to know what each piece of the puzzle weighs...

Pistons

1. 235.85 g
2. 233.51
3. 233.71

wrist pins

1. 83.57
2. 83.49
3. 83.62

Rods

1. 460.27
2. 463.91
3. 461.39


lightest rod with heavist piston/ pin combo

1. 779.61
2. 778.67
3. 781.03

So my rods are throwing it more then pistons... I could grind some rod and call it done?

Piccies of the offending performance parts. Hope the bling bling bespoke bits don't make you guys jealous (I just used bespoke in a sentence!)









As for fancy shmancy rotating balancing, whole assembly stuff... if it can't be done in my basement while drinking a beer, it ain't getting done! Truthfully the crank is a stock crank that was ground .20 over. I figure at the very least removing variance in the bits stuck to it will at least help somewhat. If not, meh.



Edited 1 time(s). Last edit at 06/19/2013 12:04AM by Mad Matt F.

Oh damn...

Forgot about bearings...

Tomorrow.

Fancy scale.

I bet the whole thing would work even better if you had a fourth piston!

---

Grant Hughes

It IS the total weight that counts. The way I see it getting it within 2 grams is fine.. Yeah sand on that nice pad on the end of the small end, 2g off the "heaviest" rod and mix and match you'll be within 2g,,
Call it good and assemble that beast

Note that your piston/pin/rod combo is less by around 100g of a Volvo B23 turbo piston..or rod---alone..

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

All I see now is death valley...

---

Grant Hughes

Grant, I have a fourth piston, but a can't seem to find where it goes!?

mmm the death valley is a local over hopped thing that I just picked up as part of my "father's day special" (my daughter is just a few months older then yours...)

John, see I told you the justy had potential!

778.66
778.67
778.67

man that's s nice scale. .. borrowed from the lab.

on the heaviest rod I removed the upper boss and still had to take some off the big end.

John as for what I'm worried about, think of the children! imagine the justy cresting the hil at the tall pines spectator stage, and I miss a shift into 3rd. intending to wow the fans I don't lift and the justy roars to 120000000 rpm, the heavy piston breaks free of the rod, removes the head (held on with zip ties) and rockets off into the crowd. just think of the horror!

Quote
Mad Matt F
778.66
778.67
778.67

man that's s nice scale. .. borrowed from the lab.

on the heaviest rod I removed the upper boss and still had to take some off the big end.

John as for what I'm worried about, think of the children! imagine the justy cresting the hil at the tall pines spectator stage, and I miss a shift into 3rd. intending to wow the fans I don't lift and the justy roars to 120000000 rpm, the heavy piston breaks free of the rod, removes the head (held on with zip ties) and rockets off into the crowd. just think of the horror!

the horror!




the horror....


_{the horror}

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.



Edited 1 time(s). Last edit at 06/19/2013 07:00PM by john vanlandingham.