Apeiron

All you need is an old lathe bed, an old connecting rod hone, a degree wheel, a timing light, a couple of dial indicators, a variable speed electric motor and a speedometer from a 74 Mercury.

Sonix

iTrader: (1)

hey MacGyver, I think you left out that incredibly important roll of tape.

Apeiron

The tape is there for cosmetic purposes only.

Streetiron85

So, how's it done??
What do you use the connecting rod hone for?
Can I use pedal power instead of the VS electric motor?

Merlin

Someone has made an attempt at dynamic balancing, using displacement measurements at varying RPMs to determine the amount of imbalance. The trouble is that a dial indicator is a poor substitute for an active displacement transducer.

The Mercury speedo is a luxury/overkill - It could have been from a regular Ford.

Technically, it could be done. It's not very technical, though. Still, amusing.

Sonix

iTrader: (1)

I'm kinda wondering if this is serious or a joke...? Ape, is that your garage ? (then i'd ask if you seriously own like 200 connecting rods...)

Scheister

so no tooth picks or rubber bands are used?

kdrolt

I like it and actually it's very technical; it mimics the pre-computer method(s) used before electronic data aquistition (and mechano-electric transducers). "Poor substitute" really depends on how well he can measure the vibration modes, and how well he does at mitigating them with balance weights. Oil-filled (damped) gauges might help if you aren't already using them. You might also need to add at least one pair of transverse meters to measure vertical vibration, to add to the lateral ones I think I see in the attached jpeg. Adding a Strobotach from EG & G to the mix might also be useful.

Old school doesn't mean it can't work well.

It would be neat to measure compare measurements before/after balancing on this rig vs a modern one, just to see how well it works. You could also measure the rotating asm response to using different torsional dampers, and therefore add to the torsional damper threads here.

I agree on the speedo comment <g>.

How high in rpm can you (safely) go?

Apeiron

No, that's not my garage. My connecting rod collection consists of only something like 60 rods.

That's a balancer my cousin built for his shop. It works pretty much like the old school balancers did in the days before electronic balancers were available.

Using it is more involved than using a modern unit. There's no computer to tell you what's going on, so you need to interpret the displacement measurements yourself. If you don't know what you're doing, you can turn a crank to trash in a hurry.

Another relatively minor tedious part is that it doesn't have a drill head mounted on it, so you have to remove the crank to drill it.

I don't know how fast it will spin safely. You can see a couple of kill switches mounted below the dial indicators to shut the motor down if there's too much movement, but they've never actually gone off. If it's too badly balanced at the start, you'll know it before it hits 100 RPM.

Merlin

You'd have to be quick watching the indicators.

As for the vertical deflection comment, that would be a good idea, but the cradles don't appear to be designed to allow vertical movement (well, at least anything beyond the arc of the radius arms).

Just a curiosity, but what is he using to couple the drive to the crank/weight assembly? I'd hope it is a very flexible coupling, like one used for an encoder.

If you're not doing production level throughput, it should work just fine. It's no worse than the old electrodynamic dynamometers. They were just as accurate as anything "modern", in the right hands. That assembly is similar, in that it is only as good as the "computer" running it. The only difference is that the "computer" running that example is biological, which can actually be better.

Aircraft or instrument bearings for the wheels? I would think they would have to be reasonably small to minimize drag.

Care to lend the secret of the speedo? It's still worth a grin to see that on there.

Apeiron

The dial indicators are frozen with the timing light to read the displacement at a given angle of rotation.

I'm not sure what kind of bearings he's using, and I can't remember right now how the crank is coupled. I'll get more details the next time I talk to him.

The speedo is just used as a tach. It's easier to find a cable driven speedometer than a cable driven tach.

fin170703

I've got an empty washing up bottle and a piece of string could i make one with that. lol.

You lot amaze me everytime i come one this website , dont mean to blow smoke up your ***** but it makes me feel like an idiot when i see the knowlege you lot have. still good to know your there when a problem flares up