Engine builders' advice req'd - removable piston weights? - Page 7 - PeachParts Mercedes-Benz Forum

Adriel · #91 11-12-2013, 12:03 PM

Quote:

Originally Posted by Stretch

I think I'll swap the combined set in cylinder 3 with cylinder 4 so that the heaviest is next to the flywheel.

Looks good!

Think I would have gone to the same O.C.D. behavior as you, as got to be close to perfect as possible!

Why put the heaviest to the flywheel?

vstech · #92 11-12-2013, 12:17 PM

Quote:

Originally Posted by Stretch

Thanks for the vote of confidence - I hope I haven't cocked it all up and taken out too much strength. Still this is the only way to learn!

Here's my final configuration

I think I'll swap the combined set in cylinder 3 with cylinder 4 so that the heaviest is next to the flywheel.

I'd whittle down the con rod's weight a gram... shouldn't take much.
which end is heaviest?

Simpler=Better · #93 11-12-2013, 12:29 PM

Quote:

Originally Posted by Stretch

Have you got a link for your project?

(I guess you're on STD?)

I spent a good half hour grinding the plate, then taking it the shop, machine setup, turning so it would be pretty, and if you wanted to count it milling down the vac cover and brazing it up pretty

I probably gained like 0.75HP there

Stretch · #94 11-12-2013, 04:01 PM

Quote:

Originally Posted by Adriel

Why put the heaviest to the flywheel?

In the simple - over simple case - the crank is like a long beam with a big weight on the end (flywheel). Although the beam is supported at several points (main bearings) it will have a tendency to bend like a banana along its whole length. This is an exaggerated example of behaviour but there is usually a detectable vibration that is closely related to the length of the crank.

If you're adding four "bouncing" weights (pistons going up and down) at four different points along the beam you are better off putting the heaviest of these bouncing weights at the closest position to the big weight at the end of the beam (flywheel). This is because the effect of the heaviest piston is the least on the whole banana bending effect (that you might be able to imagine) of the beam when it is closest to the big dominating weight at the end (flywheel).

If you do the opposite and stick the heaviest piston furthest away from the flywheel then you might find that you exaggerate the banana bending effect and excite this vibration that is proportional to the length of the crank.

Generally speaking for most "normal" situation vibrations related to large parts of a machine are more of a problem because they often happen within "normal" operating speeds. So you want to avoid exciting / influencing / provoking the big stuff!

This whole model / approximation of bouncing weights on a beam with a big weight attached to the end of it supported at various points along its length, however, gets really complicated when you include the effects of combustion and sudden changes in engine speed...

Stretch · #95 11-12-2013, 04:06 PM

Quote:

Originally Posted by vstech

I'd whittle down the con rod's weight a gram... shouldn't take much.
which end is heaviest?

The conrod in the set up for cylinder 3? I could do - it would be nice. I'll have a look at it tomorrow

Do you mean which end of the conrod is heaviest? If so I feel a smart arse response coming on - the big end!

Stretch · #96 11-12-2013, 04:08 PM

Quote:

Originally Posted by Simpler=Better

...
I probably gained like 0.75HP there

With out a doubt - you'll be flying along.

Did you do any porting work and unswept volume balancing acts on the head?

Simpler=Better · #97 11-12-2013, 08:15 PM

Quote:

Originally Posted by Stretch

With out a doubt - you'll be flying along.

Did you do any porting work and unswept volume balancing acts on the head?

What do you think I am, a ham shanker?

My OM617 Build

When it goes from storage to wrenching I'll probably post up a duplicate build thread here

vstech · #98 11-12-2013, 08:22 PM

Quote:

Originally Posted by Stretch

The conrod in the set up for cylinder 3? I could do - it would be nice. I'll have a look at it tomorrow

Do you mean which end of the conrod is heaviest? If so I feel a smart arse response coming on - the big end!

no arse... I mean which end compared to all the others is heaviest? is it the big end that's 2 grams heavier than the rest, or the small end or is it equal?

cause like I said early in this thread, the big end is counted differently from the small end on the balance of the whole....

Stretch · #99 11-13-2013, 03:26 AM

Quote:

Originally Posted by vstech

no arse... I mean which end compared to all the others is heaviest? is it the big end that's 2 grams heavier than the rest, or the small end or is it equal?

cause like I said early in this thread, the big end is counted differently from the small end on the balance of the whole....

I thought you meant something like that - I've been avoiding that making that comparison because (and you may have noticed this with me) I tend to get sucked into things a bit and I end up wasting my limited time...

...I'm kind of hoping that making an over all weight comparison I'm gonna be more or less good.

Stretch · #**100** 11-13-2013, 03:29 AM

Quote:

Originally Posted by Simpler=Better

What do you think I am, a ham shanker?

My OM617 Build

When it goes from storage to wrenching I'll probably post up a duplicate build thread here

Ah ha there it is!

(I don't really think you'd be calling yourself that if you knew what I meant when I say it! It is a reference to masturbation {don't you know})

Simpler=Better · #**101** 11-13-2013, 10:28 AM

Quote:

Originally Posted by Stretch

Ah ha there it is!

(I don't really think you'd be calling yourself that if you knew what I meant when I say it! It is a reference to masturbation {don't you know})

I spend time and money working on 30 year old 100hp cars, when I could have built a hotrod turbo 4.6L V8 gasser for about the same investment. Technically, all I ever do is shank around in the shop...just with diesels and money

But yeah, I think Ham Shanker is the funniest way I've heard it put and it makes me snort so we're good

Stretch · #**102** 11-13-2013, 01:34 PM

Quote:

Originally Posted by Simpler=Better

I spend time and money working on 30 year old 100hp cars, when I could have built a hotrod turbo 4.6L V8 gasser for about the same investment. Technically, all I ever do is shank around in the shop...just with diesels and money

But yeah, I think Ham Shanker is the funniest way I've heard it put and it makes me snort so we're good

Cool - I didn't want you to have a nasty shock...

...so I guess you're the man to take on my direct injection OM617 project? (that's all in my head at the moment - a bit like mega squirt for your diesel)

Simpler=Better · #**103** 11-13-2013, 03:04 PM

Quote:

Originally Posted by Stretch

Cool - I didn't want you to have a nasty shock...

...so I guess you're the man to take on my direct injection OM617 project? (that's all in my head at the moment - a bit like mega squirt for your diesel)

When the time comes I can turn injector holders to replace the prechambers.

Fair warning, I'm beyond slow when it comes to making parts

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