Connecting rod balancing

[1crosscut]

A few days ago old31 started a thread on balancing pistons and rods. The post sort of veered off track but still had lots of interesting information.
https://www.fordbarn.com/forum/showthread.php?t=321699

So sort of circling back to the original question I'd be interested in seeing pictures of the set ups that folks are using to balance
their rods.
Are you making your own or using a commercial set up?

[johnneilson]

Pete posted up a video link that shows pretty good balancing a full rotating assembly
The rods are done with a stand to weigh each end individually

Since you are interested in balancing I would recommend reading the ISO balancing standards and theory for a better understanding of the subject

Have a Happy New Year
J

[1crosscut]

I understand the concept and how to go about it. I was just wanting to see what others have set up to do theirs.
In his video he sands and grinds the rods and pistons to take the excess weight off. Would make me nervous to have that around the babbit.

[Richard Knight]

I am interested in this thread also. I have an unrestored 29 Briggs with 47k. Leaked so much oil I had to take it out even though it ran great. The leak was the failed gasket between the block and flywheel housing. Not the rear main bearing. So back to the rods. I have been thinking about balancing the rods using my digital scale. What I found out very quickly is when trying to repeat weights placement location on the scale changed the weight immensely. So I machined up some pins to locate the rod on scale. Well that didn't work. So on to u tube for balancing videos. I found a short video of simple set up which I could copy. Video explained the key points. So I made a fixture, super glued it to my gram scale. Set up a support for the non weighing end of the rod. The bottom line is if you carefully place the rod on the scale carefully in the same exact location the weights are repeatable. What I found is that all the small ends of the rods are within 3 grams. Same for the big ends. 3 grams. Which truly amazes me. I have been looking on Vince garage for specs on rods but have not found any yet. I would be glad to post pictures but haven't figured that out yet!

[ursus]

Originally Posted by 1crosscut

I understand the concept and how to go about it. I was just wanting to see what others have set up to do theirs.
In his video he sands and grinds the rods and pistons to take the excess weight off. Would make me nervous to have that around the babbit.

Excellent point! I have had exactly that experience where very hot bits of sanding grit and removed metal become embedded into the surface of exposed babbit and this is detrimental to the life of both babbit and the associated bearing journal. I have since protected the babbit with a combination of masking tape and heavy grease in order to eliminate this kind of insult to the bearing surfaces.

[Bob Johnson]

Sponsored Links (Register now to hide all advertisements)

My method.

http://www.modelahouse.com/images/rod-balance.pdf


Bob

[BRENT in 10-uh-C]

Originally Posted by 1crosscut

I understand the concept and how to go about it. I was just wanting to see what others have set up to do theirs.
In his video he sands and grinds the rods and pistons to take the excess weight off. Would make me nervous to have that around the babbit.

Originally Posted by ursus

Excellent point! I have had exactly that experience where very hot bits of sanding grit and removed metal become embedded into the surface of exposed babbit and this is detrimental to the life of both babbit and the associated bearing journal. I have since protected the babbit with a combination of masking tape and heavy grease in order to eliminate this kind of insult to the bearing surfaces.

To begin with, balancing rods or pistons is something that can be frustrating as you are removing very small amounts of weights and you often overshoot your target where that item now becomes your new lightest piece that you must match the other 3 to. Also, if someone were to put tape or grease on the piece you are balancing, it would alter the weight matching process where it would be fruitless.

From my vantage point, if you guys are experiencing heat that is hot enough to imbed media and metal into the cast bearing metal, then I believe you are being WAY more aggressive than need be to remove the amount needed. When I/we pour rods, the poured rods weight differences can be huge but we weight-match them and group them into sets where I am less than 5 grams or so between my heaviest and my lightest rod. Think about the size of the pile of metal filings you have that weighs 5 grams!! That pile of metal filings is probably only a tad more than the amount of salt that people put onto their evening meal is!! No need to use excessive force or prolonged periods with a grinder trying to remove metal.

The way we do it is by using a vertical belt sander on a stand to remove the bulk on the beams of the rod. As I said above, generally speaking we are removing less than 5 grams (...again think about what weighs 5 grams and how much that really is!!) and so all you are really doing is deburring the beam and removing potential stress riser areas however nothing structural is compromised. After the initial weighing, the lightest rod becomes our tare weight and we zero out our scale and individually weigh and grind just enough to match the other three weights to the lightest one. We will typically stop when we are within 1 gram of each other. While this isn't as critical on an in-line engine, we have a little shop-built stand that we support the little end of the rod and just weigh the big end of each rod on a digital scale and compare all four rod weights. Then we remove just a small amount from the rib on the cap alternating between the two until we get the weights to be as near to 0.00 as possible. Removing this last amount of material will generally be about a paper thickness for about ¼" in length which does not compromise any structural integrity for 99% of the usage most Model-A engines see. As a final check, we will flip to the small end weights and just check them and most will come-in at under a half gram differential. We rarely bother with correcting that difference between them on that end simply because Ford allowed 1 gram differential between the rods on either end.

FWIW, at no time is any portion of the rod getting too hot where you cannot hold it in your hand. These will be see temps hotter than that in a running engine. Secondly, we always do a final rinse before assembly which will remove any media debris or removed metal however just a shot of compressed air over all areas of the rod will do the same.

[goodcar]

[I]To begin with, balancing rods or pistons is something that can be frustrating as you are removing very small amounts of weights and you often overshoot your target where that item now becomes your new lightest piece that you must match the other 3 to.

This reminds me of a kid in Ag class who built a feed bunk with one leg too short, so he cut the other three off. He didn't get it right, so he kept cutting until the bunk turned into a trough.

[Ramman]

xacally why there's 3 legs on a milking stool.

[1crosscut]

Bob,
Thanks for posting pictures of your set up.

[Dan McEachern]

Here is a terrible picture of my rod balancing setup. Stewart Warner balance scale with the fixture for supporting the rod from the pin end and the big end resting on the scale platform. As Brent mentioned, for poured rods, I assemble them, rough bore and face the thrusts, and then play the sorting game, matching big end and total weight into sets that I feel can be balanced. It is a give and take process, as you need to keep in mind that a big end 5-10 grams heavy will also reduce the total weight by that amount when corrected. How you support the rod on the scale will make a BIG difference in the repeatability of your measurements. A string from the ceiling with a hook is a good way to hang the small end for starters. Apologies for the poor picture, but its all I could find.

[J and M Machine]

Originally Posted by 1crosscut

A few days ago old31 started a thread on balancing pistons and rods. The post sort of veered off track but still had lots of interesting information.
https://www.fordbarn.com/forum/showthread.php?t=321699

So sort of circling back to the original question I'd be interested in seeing pictures of the set ups that folks are using to balance
their rods.
Are you making your own or using a commercial set up?

This is a "Commercial set up" We use
https://www.jandm-machine.com/balancing.html
https://www.cwtindustries.com/multi-bal%205500.htm

[Pete]

Originally Posted by Dan McEachern

Here is a terrible picture of my rod balancing setup. Stewart Warner balance scale with the fixture for supporting the rod from the pin end and the big end resting on the scale platform. As Brent mentioned, for poured rods, I assemble them, rough bore and face the thrusts, and then play the sorting game, matching big end and total weight into sets that I feel can be balanced. It is a give and take process, as you need to keep in mind that a big end 5-10 grams heavy will also reduce the total weight by that amount when corrected. How you support the rod on the scale will make a BIG difference in the repeatability of your measurements. A string from the ceiling with a hook is a good way to hang the small end for starters. Apologies for the poor picture, but its all I could find.

We use the exact same setup as Dan McEachern. The whole works came with the balancer back in the 50's.
We weigh bob weights on the same scale.
We have the scale calibration checked periodically by a metrology company.