OS .25fx RPM
05-16-2010, 11:21 AM
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OS .25fx RPM
I have an OS .25fx with an 8x6 APC prop. engine is one season old with 3 quarts run through it.
My question is: what kind of RPM can one expect from this engine and prop combination?
After a debacle with poor storage techniques and rusty bearings, A friend of mine in the "technology" field offered to coat my new bearings with an extremely low friction, chemically impervious dry lubricant.
I was doing some bench testing after putting in the new coated bearings and wanted to compare the new readings with my old ones....I can't find my old readings.
Here is what I have for data with the new bearings on a stock engine, SIG 2-stroke 15% nitro - 20% oil:
(Not running lean)
16,000 max RPM and 2200 idle. (8x6 prop), Static thrust: 3lb 4oz, and a wind speed of 59 MPH (measured 6" behind engine)
My question is: what kind of RPM can one expect from this engine and prop combination?
After a debacle with poor storage techniques and rusty bearings, A friend of mine in the "technology" field offered to coat my new bearings with an extremely low friction, chemically impervious dry lubricant.
I was doing some bench testing after putting in the new coated bearings and wanted to compare the new readings with my old ones....I can't find my old readings.
Here is what I have for data with the new bearings on a stock engine, SIG 2-stroke 15% nitro - 20% oil:
(Not running lean)
16,000 max RPM and 2200 idle. (8x6 prop), Static thrust: 3lb 4oz, and a wind speed of 59 MPH (measured 6" behind engine)
05-16-2010, 01:37 PM
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RE: OS .25fx RPM
Aaaaaaaaaaaaaaaaaaah Grasshopper:
You may get a little beat up here with this crowd, but its the best place in the world to go. Right off, quit the test cause regardless you can not compare apples to apples. For a reasonable test, you would have to start with the old bearings, or new and get a reading using them. Then test with the new treated bearings on the same day, same fuel, same carb setting if possible, and as close to the same time as possible. That will get you in the ball park to a reasonable bench test. The piston and crank pin will have moved a tiny bit with the bearing change, so it could be argued the test is not valid for this reason, atmosphere differences, etc. and be correct.
The best test would be a new bearing by the same manufacturer stock, and then compare it with a treated new bearing. How, you'r gonna have to be creative here. One way, fix the bearing in place, run a shaft through it, spin with a electric motor and compare the rpm's. Maby drive the shaft with a electric motor and check the difference with a watt meeter. The better bearing will run on less watts. I'm sure the bro's will offer up as good or better alternatives once someone puts their foot in their mouth. Oh well, ENJOY, bro 117
You may get a little beat up here with this crowd, but its the best place in the world to go. Right off, quit the test cause regardless you can not compare apples to apples. For a reasonable test, you would have to start with the old bearings, or new and get a reading using them. Then test with the new treated bearings on the same day, same fuel, same carb setting if possible, and as close to the same time as possible. That will get you in the ball park to a reasonable bench test. The piston and crank pin will have moved a tiny bit with the bearing change, so it could be argued the test is not valid for this reason, atmosphere differences, etc. and be correct.
The best test would be a new bearing by the same manufacturer stock, and then compare it with a treated new bearing. How, you'r gonna have to be creative here. One way, fix the bearing in place, run a shaft through it, spin with a electric motor and compare the rpm's. Maby drive the shaft with a electric motor and check the difference with a watt meeter. The better bearing will run on less watts. I'm sure the bro's will offer up as good or better alternatives once someone puts their foot in their mouth. Oh well, ENJOY, bro 117
05-16-2010, 03:00 PM
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RE: OS .25fx RPM
I'm not even sure the coating made any difference. I am really just looking for others' knowledge as far as the max rpm (for that prop) on that engine.
If the difference between numbers is only a few hundred, then I'm not concerned, but if the average max RPM for that engine, fuel and prop is only something like 14,500 and I'm getting 16,000 then further testing will be needed to be sure that the product will be beneficial.
If the difference between numbers is only a few hundred, then I'm not concerned, but if the average max RPM for that engine, fuel and prop is only something like 14,500 and I'm getting 16,000 then further testing will be needed to be sure that the product will be beneficial.
