I'm balancing my TR7 750 engine, bought electronic scales 0 to 1000 grams .10 gram incriments. balanced rod bolts, pistons complete, no problems understand how to work out my 85% factor but now on to the rod ends. I have machined inserts for the conrod ends to support them horizontaly using a magnetic dial indicator stand on a steel bench with 1/4" rod passing through the centre of the inserts so the rod is horizontal and "plumb" The problem is every time I put the rod end on the middle of the scales (which I have marked with a spot) I get a different reading and or the weight reading creaps up or down in .10 of a gram to 5 grams. I lift off the rod end carefully replace it and yes another reading on the scales! O.K. the scales are stuffed, no I then put ANY object on the scales and the reading in constant. Even left the rod on the scales overnight and the reading stablised but when you lift it off and put it back on a different reading and or it creaps. Am I not seeing something at my wits end. HELP! Retired-fireman stressed and in need of help!
Retired, the fixtures I've seen also support the small end with a little gallos looking affair sitting on the scale plate with a small end filler with hole centered and horizontal pin much like I'm envisioning that you did on big end. With rod free to swing on both ends and horizontal you should be getting repeatable wts. I've tried your way with small end on scale and had same results as you, just haven't bothered to fabricate jig yet as balancing rods isn't as near to reality as I had hoped...Mark
Re: balancing conrods#91696 05/09/065:15 am05/09/065:15 am
Thanks Markster, I take it you mean to support one end of the rod on the gallows looking device which is sitting on the scales. The rod is suspended from the gallows by wire wrapped around each side of the shaft that projects either side out of the rod. The insert for the rod looks like a cotton reel with a 1/4" rod through it's centre. Meanwhile the other end of the rod would have a simular device in its eye and balance it's central rod between a support which is adjusted up or down so the rod is weighed when it's exactly horizontal? There is a book I've come across "Triumph Tuning by Stan Shenton" it has an illistration on page 32 but it does't completely show what they are up to with the weighing of the rod. I'm starting to relise how delicate the ends are to balance correctly and would appreiciate any more info from anyone who has done this or seen someone doing it or any links to illistrations. I have checked all the thread I could find on here and can't find references to balancing the rod ends. retired-fireman Thanks!