GO-300-D free play

Tom-D

Tom-D

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Tom-D
what is the amount of free play allowed for the GO-300.

how to measure ?
 
Snowmass said:
Free play of what? I owned two. Breaking compression rings and fixing was usual maintenance.
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Free play of the gear box.

show us where the measurement is taken.

MM doesn't tell us.
 
I would not be surprised if people just fly the GO-300 and ignore backlash if the gears look good and no cracks. Are new gears even available?.
 
Snowmass said:
I would not be surprised if people just fly the GO-300 and ignore backlash if the gears look good and no cracks. Are new gears even available?.
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I do not know of any.
ignorance is bliss, ?
 
Snowmass said:
Well if C-175s are flying I bet those gears are quite worn. How could they not be.
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Problem is, lack of data. I once did a phone conversation that TCM said 1/4"

I was hoping we could find source for the measurement
 
I suspect I would keep flying a C-175 regardless of gear play if teeth looked good and passed Magnaflux. But I put the laws of physics above the laws of men. And if TCM (and all the rest) were all that smart why would we have ADs? In fact what would happen if larger than approved tooth gap?
 
Snowmass said:
And if TCM (and all the rest) were all that smart why would we have ADs? In fact what would happen if larger than approved tooth gap?
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There is something called torsional vibration, or TV, and it destroys reduction gearing in aircraft engines. That crankshaft turns jerkily as the compression and combustion cycles slow and accelerate it, while the propeller wants to turn at a steady rate due to its mass. On a car's engine the flywheel is bolted solidly to the crankshaft to dampen those pulses, and the rest of its drivetrain is flexible enough to absorb what's left of the TV. The geared aircraft engine has no flywheel other than the prop, and so the prop has to fight the TV through the gears, and if the lash is excessive those gears can fail suddenly and catastrophically. How hard can you drive a nail if you can only move the hammer one inch? How hard can you hit that nail if you swing it two feet? Those gear teeth feel the wham when the lash gets too big. The only rigid flywheel a geared engine has it its crankshaft, and it's not effective enough due to a low momentof inertia.
TV is a big deal in homebuilts. It's always coming up over at homebuiltaircraft.com. There have been hundreds of auto engine conversions using various reduction methods to allow the auto engine to spin up to rated RPM and generate rated HP while keeping prop RPM in a usable range. Some of them have failed spectactulary and caused accidents that killed people. Gears, chains, timing belts, V-belts have all been used. Even with belts TV is a problem. I installed a Subaru conversion in a Glastar, using a wide timing belt, and that engine would resonate badly at 1400 RPM or any multiple thereof, as the propeller's mass would fight the engine's firing pulses. That belt had to be kept quite tight, even with an aluminum flywheel on the crankshaft and using a light composite prop. V-belts have been more successful because they'll slip if the TV is too bad, but their efficiency is lower. Decades ago Geschwender sold Ford V-8 conversion kits using a Morris Hy-Vo chain, and it was fairly successful. Several were used in cropsprayers. That chain had a self-wedging function as it curved around the sprockets, removing all play.

If GM and Ford and Chrysler were building aircraft engines, they would have ADs, too.
 
But how many GO-300 engines are still in use? How long since new gears available. I suspect many have out of spec lash so maybe tolerance is too tight. I suspect most (almost all) engines have out of spec lash as these are very old engines.
 
Snowmass said:
But how many GO-300 engines are still in use? How long since new gears available. I suspect many have out of spec lash so maybe tolerance is too tight. I suspect most (almost all) engines have out of spec lash as these are very old engines.
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Well, your vast experience would let it go, I suppose, and then when it finally grenaded you'd answer to the judge and jury. Tom has no desire to do that, and he's not going to risk everything he owns just to keep an ancient engine flying.

First you criticize the manufacturers for having ADs, then criticize them for being too fussy with their specs.
 
Snowmass said:
But how many GO-300 engines are still in use? How long since new gears available. I suspect many have out of spec lash so maybe tolerance is too tight. I suspect most (almost all) engines have out of spec lash as these are very old engines.
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How would we know without a measurement?

I think the measure isn't a inch of travel measurement. It will be a amount of backlash between the two gears.
 
Dan Thomas said:
There is something called torsional vibration.
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This will not occur when the gears are loaded. The chatter occurs when the gears have a space between them.
I maintained and flew a C-175 for many years, the owner would not allow the engine to idle, he would have the engine to have some power or negative torque at all times.
 
Dan Thomas said:
There is something called torsional vibration, or TV, and it destroys reduction gearing in aircraft engines. That crankshaft turns jerkily as the compression and combustion cycles slow and accelerate it, while the propeller wants to turn at a steady rate due to its mass. On a car's engine the flywheel is bolted solidly to the crankshaft to dampen those pulses, and the rest of its drivetrain is flexible enough to absorb what's left of the TV. The geared aircraft engine has no flywheel other than the prop, and so the prop has to fight the TV through the gears, and if the lash is excessive those gears can fail suddenly and catastrophically. How hard can you drive a nail if you can only move the hammer one inch? How hard can you hit that nail if you swing it two feet? Those gear teeth feel the wham when the lash gets too big. The only rigid flywheel a geared engine has it its crankshaft, and it's not effective enough due to a low momentof inertia.
TV is a big deal in homebuilts. It's always coming up over at homebuiltaircraft.com. There have been hundreds of auto engine conversions using various reduction methods to allow the auto engine to spin up to rated RPM and generate rated HP while keeping prop RPM in a usable range. Some of them have failed spectactulary and caused accidents that killed people. Gears, chains, timing belts, V-belts have all been used. Even with belts TV is a problem. I installed a Subaru conversion in a Glastar, using a wide timing belt, and that engine would resonate badly at 1400 RPM or any multiple thereof, as the propeller's mass would fight the engine's firing pulses. That belt had to be kept quite tight, even with an aluminum flywheel on the crankshaft and using a light composite prop. V-belts have been more successful because they'll slip if the TV is too bad, but their efficiency is lower. Decades ago Geschwender sold Ford V-8 conversion kits using a Morris Hy-Vo chain, and it was fairly successful. Several were used in cropsprayers. That chain had a self-wedging function as it curved around the sprockets, removing all play.

If GM and Ford and Chrysler were building aircraft engines, they would have ADs, too.
Click to expand...
The more recent (and successful) auto conversion do take into account 'rotational hammer' and don't have the issues of the past. One interesting thing is that one should use 'odd' ratios to prevent a recurring lineup of vibration.
 
Tom-D said:
This will not occur when the gears are loaded. The chatter occurs when the gears have a space between them.
I maintained and flew a C-175 for many years, the owner would not allow the engine to idle, he would have the engine to have some power or negative torque at all times.
Click to expand...
It will indeed occur if the gears are steadily loaded; their load will vary with the crank speed (which is horribly uneven), and the peaks will likely exceed what a designer, ignorant of TV, would have allowed for. That's why some systems that were engineered by fixing what failed end up with gears two or three times stronger than what would be calculated.
I have a friend whom I will call a 'digital driver'. She's on the gas, or off the gas. It's sickening to be in a car with her. She's gone through more transmissions in the last 20 years than all of my other friends combined. The constant hammering will destroy anything not designed for it.
 
Kenny Phillips said:
It will indeed occur if the gears are steadily loaded; their load will vary with the crank speed (which is horribly uneven), and the peaks will likely exceed what a designer, ignorant of TV, would have allowed for. That's why some systems that were engineered by fixing what failed end up with gears two or three times stronger than what would be calculated.
I have a friend whom I will call a 'digital driver'. She's on the gas, or off the gas. It's sickening to be in a car with her. She's gone through more transmissions in the last 20 years than all of my other friends combined. The constant hammering will destroy anything not designed for it.
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The GO-300 does not constantly hammer, It is constant torque. The changing of the torque occurred while changing direction
 
Dan Thomas said:
Well, your vast experience would let it go, I suppose, and then when it finally grenaded you'd answer to the judge and jury. Tom has no desire to do that, and he's not going to risk everything he owns just to keep an ancient engine flying.

First you criticize the manufacturers for having ADs, then criticize them for being too fussy with their specs.
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Sorry but my statements are not logically inconsistent but you are.

How many flying GO-300s do YOU think meet gear spec?

All this has no effect on me since the last one I flew was around 1970. My point on ADs is to point out that manufacturers, like you are not perfect, and can give incorrect advice. (Can you say Boeing?). FYI the early C-175s had seriously high CHTs but no cowl flaps. I (illegally) put cowl flaps on my plane and then got STC and sold kits for a number of years.
 
Snowmass said:
Sorry but my statements are not logically inconsistent but you are.

How many flying GO-300s do YOU think meet gear spec?

All this has no effect on me since the last one I flew was around 1970. My point on ADs is to point out that manufacturers, like you are not perfect, and can give incorrect advice. (Can you say Boeing?). FYI the early C-175s had seriously high CHTs but no cowl flaps. I (illegally) put cowl flaps on my plane and then got STC and sold kits for a number of years.
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What’s the STC number?
 
Do not have it here near your grave site where I am at moment (Glenwood Springs) but you can look it up with the FAA I think it was issued in 1960.

If you want to know how much the FAA has gone down hill all I needed to do was fly to Hawthorne CA and the FAA engineers put thermocouples on my plane loaded it to gross and the did a steep climb. They said that with the flap closed my plane exceeded CHT redline (stock configuration )but passed after flap opened. Total time two hours. Total cost zero. Also they said send in engineering drawings and we will give you a mult-plane STC. I did and they did. Try this today with the wimp FAA engineers.
 
Snowmass said:
Do not have it here near your grave site where I am at moment (Glenwood Springs) but you can look it up with the FAA I think it was issued in 1960.

If you want to know how much the FAA has gone down hill all I needed to do was fly to Hawthorne CA and the FAA engineers put thermocouples on my plane loaded it to gross and the did a steep climb. They said that with the flap closed my plane exceeded CHT redline (stock configuration )but passed after flap opened. Total time two hours. Total cost zero. Also they said send in engineering drawings and we will give you a mult-plane STC. I did and they did. Try this today with the wimp FAA engineers.
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Didn’t find it. Not on the FAA data base.

Some people modified the cowlings with louvers, and I believe the 175C came from the factory with cowl flaps. Another popular mod was increasing the lip of the lower cowling.
 
My second C-175 had the factory cowl flaps. STC is somewhere. About 2 years ago I had an inquiry from some one who found it. Not making anymore.
 
Tom-D said:
Problem is, lack of data. I once did a phone conversation that TCM said 1/4"

I was hoping we could find source for the measurement
Click to expand...

Why not call TCM?
 
The GO-300 is not the only geared engine out there. Perhaps there is a comparable unit (six cylinder, spur gears) that has a published backlash spec and could be used as guidance for the GO-300. Not as good as the real thing of course, but perhaps better than nothing?

Also, what about the modern diesels that have a reduction gear drive? Do they have published backlash specs?
 
flyingbrit said:
The GO-300 is not the only geared engine out there. Perhaps there is a comparable unit (six cylinder, spur gears) that has a published backlash spec and could be used as guidance for the GO-300. Not as good as the real thing of course, but perhaps better than nothing?

Also, what about the modern diesels that have a reduction gear drive? Do they have published backlash specs?
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Can't use the specs for one engine in another. Geared engines typically have some sort of damping, but it's specific to that engine and rpm range, and lash specs won't necessarily be the same. The GO-300 used a short quill shaft that fit inside the crank and gear to act as a bit of a spring, tuned to a six-banger of that rpm and displacement and a metal prop of specific weight and moment of inertia. Other engines will be different in many ways.
Torsional vibration is a complex, not easily understood subject. It has torn apart many homebuilders' attempts at PSRUs (propeller speed reduction units). Even the early RR Merlins had short gear life until the engineers figured it out. Gear lash is a critical item in the system.
 
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