Connecting rod weighing

[belgiquebasterd]

Made my own jig to weigh little and big ends seperately using info I found in other threads on this site as a lead, problem is I can't get consistent repeat readings, the weight differs +/- 2gr.

Picture of the jig, made the chains about 3 foot long to prevent binding issues (same as the example I found in another thread here)



Used an old bearing to hold the big end, is a little bit smaller than the big end diameter as you can see



Used an old lifter body for the small end, there is a bit of play but not much as you can see in the picture



No matter how hard I try I can't get good readings, it's driving me crazy, what am I doing wrong?

Thanks, Christof.

[Nick Campagna]

Off hand, I would say stick-slip on the bearings. Use a knife edge to hold the conrod at each end and lose the bearing and pin arrangement. IMHO.

[donc]

Off hand, I would say stick-slip on the bearings. Use a knife edge to hold the conrod at each end and lose the bearing and pin arrangement. IMHO.

x2Try to keep ctr. of rod bore centered on pin, Id shorten the chain, keep the rod as straight as you can, make sure nothing like compressor or other machine is not vibrating bench,also make sure theres no magnatism in parts that will make it hang up. You can check scale with clean dollar or whatever currency each bill should 1 gram. and no a 10 dollar bill doesnt way 10 grams LOL.

[governor]

I built one a few years ago and used roller skate bearings as they were small in dia with very little rolling resistance. I used them on both ends, with the large end having 3 in a row in the big end aligned at the parting line and the other 2 above the rod as a pivot to allow for any mis-alignment.

I would get very repeatable numbers, using my old beam paint scale.

Gov

[belgiquebasterd]

Victory, well kind off , ended up using router bit bearings to hold the rod on and can now get readings wich only vary max 0.3gr. Is this acceptable, what is the usual tolerance used when balancing rods, or do they have to be spot on?



Router bit bearings are just a touch bigger than the bolts, you can barely see them.



Thanks for the help!

[donc]

Very nice, good job.