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Posted:
Thu Jul 06, 2006 1:29 amby jsa
I'm wondering where to locate a tumble meter, which I imagine to be like a paddle wheel parrallel to the cylinder head ?
Posted:
Thu Jul 06, 2006 6:43 amby Tony
I doubt if you can buy such a thing. The problem is that there is no standard official unit of tumble to measure. So it is not really possible to build a measurement instrument with any meaningful readout.
Sure you can build a paddle wheel, and say it spins at 438 Rpm, what does that tell you exactly ?
Posted:
Thu Jul 06, 2006 7:51 amby jsa
Tony,
I planned on making something. Either a round magnet and a nearby coil to read frequency, or a little dc motor to generate a volt output. Driven by a paddle wheel or some other means.
I think frequency will be more stable long term as armature and brush wear would decay a voltage output over time.
In isolation the number is useless, however as a head is developed, tracking the measurement may reveal steps in the right or wrong direction. I would think if flow increased by 50% and tumble fell by 50% then that would be bad. Charting rpm per cfm might be educational
Just need to work out some way of fitting it to get a repeating measurement ?
Posted:
Thu Jul 06, 2006 7:45 pmby Tony
It is a really tough problem. Trying to define swirling and tumbling uneven airflows into some sort of repeatable numbers. I really don't know what the solution to the problem is.
Posted:
Fri Aug 04, 2006 10:58 amby DaveMcLain
You might want to talk to Kevin at Perf Trends because they do offer a fixture to measure tumble using their swirl meter. I don't think that there is any real standard for swirl or tumble measurments but I would say that as long as you have a quantity you'll be able to tell if you're gaining or losing swirl or tumble with your porting.
Posted:
Fri Aug 04, 2006 7:58 pmby jsa
Dave,
I've seen a picture of the performance trends fixture. They appear to take flow from the side of the bore fixture and then down into the bench ? I wonder if that would induce tumble all by itself.
Posted:
Sat Aug 05, 2006 9:40 amby DaveMcLain
That's tough to say, I have not seen that fixture in action. I guess the thing to do would be to try an experiment on your own bench using a clear cylinder. I think I would experiment with a small hole drilled through the side of the cylinder with piece of string inserted through the whole to show what the air is doing in there, might tell you something.