Aerovee Pistons

[thomasjones42]

When weighing the pistons and wristpins does anyone have any tips on what kind of scales to use.

Tom Jones
Onex #133
Aerovee turbo

[dirkverdonck]

Hello Tom,
I used an electronic kitchen scale and ended up with three pistons with exactly the same weight, one was 5 grammes off.
Installed the lightweight piston on the flywheel side to limit the impact of vibrations on the propeller bearing.
Ran my engine for the first time yesterday evening on a self made test stand, started on the second try.
Regards,
Dirk
OneX 117

[MichaelFarley56]

Hi Tom,

I used a cheap gram scale from Harbor Freight to weigh pistons, wrist pins, and rods. They were all very close and I simply matched everything up so each set was nearly identical in total weight. Worked great!

[thomasjones42]

Dirk, Mike,
Thanks for your responses. I weighed the rods before installation on a scale that weighed to one gram. They were the same weight and I went ahead and installed them and sealed the case halves. I bought a small electronic scale on Amazon that measures to .1 grams. Wrist pins appear to be identical in weight to a tenth of gram. I have two pairs of pistons in terms of weights. The heavier pair is about 5 grams heavier than the lighter pair. Weights within the respective pairs are only different by less than a gram. I'm thinking to put the pair with the least difference in respective weights on the prop end and the pair with the largest spread nearest the flywheel. I think that may mean the heavier but more closely matched pair winds up on the prop end. Do either of you (or anyone else) see anything wrong with that idea?

[MichaelFarley56]

Hi Tom,

I think your plan is a good one. With weight differences being so minor I think you'd be fine regardless but matching the two closest pairs and offsetting them such as you described should work well.

Best of luck on the engine build!

[HenryVoris]

Tom,

Perhaps I am exposing my ignorance here but, if your wrist pins, clips, con-rods, rings, etc. all match in weight... is there some reason why you would not file the heavy pistons down so they all matched too???

Aloha,

[tljones42]

I stacked up washers on the scales to equal the difference in weight of the two pairs (about 5 grams). It's a lot of metal and I did not see a way that I was comfortable with to remove that much material. After unsucessfully trying to take off less than a gram from one piston of the lighter pair I gave up. Like I said 5 grams is a lot of metal.

Tom Jones
Onex 133
AV turbo