Cedge
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- Jul 12, 2007
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I've been working toward getting the little Victorian engine ready for an upcoming show. While I am working on it, I decided to do some upgrading to the engine such as a new fuel system and the 3 ball governor I shared in another thread. I also modified the linkage that locks out the push rod when the governor hits a limiting point. This meant I'd have to disassemble the front end of the engine several times to check and adjust as the new pieces were fitted.
I'll admit to a mistake at this point in things. I chose to use brass rod in the expansion arms of the governor. This proved to be a lousy idea since I'd underestimated the forces the 3 swinging balls would generate. Yup.... you guessed it. The rods failed, allowing the balls to swing, which generated some rather disturbing action as they beat against the engine. No damage to anything, but it sounded like it was going to dismantle the poor thing before it stopped.
Now I definitely had to disassemble the front end, which included the front bearing stand and points, the flywheel and the governor. No big deal, 3 minutes and it's stripped. Re-solder the arms on the governor, reassemble the components and we're ready to run again. WROOOOOONNNNGGGG!!!
At this point nothing but the point timing has been disturbed, yet when I tried to start the engine, it would fire, jump and them fire again with a HUGE backfire. This is an engine that 10 minutes ago was in fine tuning for running in hit and miss mode. Now it's TDC indicator is dead on with a huge load of compression, the cam setting is perfect and the secondary ignition spark is firing well within the exhaust cycle. The points and the plug are sparking right on schedule... at 5° before TDC. In short.... everything obvious is as it should be but, I'm getting one clean hit and then a loud backfire before everything comes to a dead stop. I fought this problem all last evening before cutting the shop lights and going to bed.
Keep in mind, no settings had been changed from when the motor was running like a top. I was beginning to think thoughts like bent connecting rod or perhaps a broken wrist pin, meaning serious surgery and some difficult machining, all in a very short time before the upcoming show. Not a pretty thought.
Anyone guessed the solution yet?
The flywheel on this engine uses 6 tiny 2-56 hex head capscrews to secure a wedge lock to hub. These 6 screws have been in use since the first install of the flywheel. The repeated action of taking the flywheel on and off the machine had worn the faces of the heads, allowing them to slip a little when the nut driver tightens them down. You really couldn't feel it, but the problem was preventing them from locking down tightly.
Anyone catching where this is going?
I normally start the engine with a battery powered drill motor, but for troubleshooting I began turning the flywheel by hand. All of a sudden the spark ignited the fuel and the crank spun hard while the flywheel stayed stationary in my hand..... one hit.... one backfire...dead stop..... HUH? Repeated these steps 3 more times with the same results, so that I knew I wasn't just seeing things.
Turns out the flywheel was just snug enough to overcome normal compression but was too loose to hold its grip when the firing cycle began. The engine would fire, the crank would spin within the hub of the flywheel and then it would try to fire into the the next 4 stroke sequence. Since the flywheel was no longer contributing momentum to carry on the cycle, the moment it tried to fire the second time, the explosion forced the crank to spin backwards, opening the exhaust valve without benefit of the normal expansion stroke, thus the loud backfire.
Solution.... replace 6 small 2-56 cap screws and tighten up the flywheel. Once that was completed, the engine one again ran like a small well tuned sewing machine.
Notes to self....
Sometimes an obvious component failure is only coincidental to the actual mechanical problem.
Brass is not a very good choice of metal if you've underestimated the stresses it will have to handle.
These little machines know many more ways to make you feel foolish than you can ever possibly anticipate.
Steve
I'll admit to a mistake at this point in things. I chose to use brass rod in the expansion arms of the governor. This proved to be a lousy idea since I'd underestimated the forces the 3 swinging balls would generate. Yup.... you guessed it. The rods failed, allowing the balls to swing, which generated some rather disturbing action as they beat against the engine. No damage to anything, but it sounded like it was going to dismantle the poor thing before it stopped.
Now I definitely had to disassemble the front end, which included the front bearing stand and points, the flywheel and the governor. No big deal, 3 minutes and it's stripped. Re-solder the arms on the governor, reassemble the components and we're ready to run again. WROOOOOONNNNGGGG!!!
At this point nothing but the point timing has been disturbed, yet when I tried to start the engine, it would fire, jump and them fire again with a HUGE backfire. This is an engine that 10 minutes ago was in fine tuning for running in hit and miss mode. Now it's TDC indicator is dead on with a huge load of compression, the cam setting is perfect and the secondary ignition spark is firing well within the exhaust cycle. The points and the plug are sparking right on schedule... at 5° before TDC. In short.... everything obvious is as it should be but, I'm getting one clean hit and then a loud backfire before everything comes to a dead stop. I fought this problem all last evening before cutting the shop lights and going to bed.
Keep in mind, no settings had been changed from when the motor was running like a top. I was beginning to think thoughts like bent connecting rod or perhaps a broken wrist pin, meaning serious surgery and some difficult machining, all in a very short time before the upcoming show. Not a pretty thought.
Anyone guessed the solution yet?
The flywheel on this engine uses 6 tiny 2-56 hex head capscrews to secure a wedge lock to hub. These 6 screws have been in use since the first install of the flywheel. The repeated action of taking the flywheel on and off the machine had worn the faces of the heads, allowing them to slip a little when the nut driver tightens them down. You really couldn't feel it, but the problem was preventing them from locking down tightly.
Anyone catching where this is going?
I normally start the engine with a battery powered drill motor, but for troubleshooting I began turning the flywheel by hand. All of a sudden the spark ignited the fuel and the crank spun hard while the flywheel stayed stationary in my hand..... one hit.... one backfire...dead stop..... HUH? Repeated these steps 3 more times with the same results, so that I knew I wasn't just seeing things.
Turns out the flywheel was just snug enough to overcome normal compression but was too loose to hold its grip when the firing cycle began. The engine would fire, the crank would spin within the hub of the flywheel and then it would try to fire into the the next 4 stroke sequence. Since the flywheel was no longer contributing momentum to carry on the cycle, the moment it tried to fire the second time, the explosion forced the crank to spin backwards, opening the exhaust valve without benefit of the normal expansion stroke, thus the loud backfire.
Solution.... replace 6 small 2-56 cap screws and tighten up the flywheel. Once that was completed, the engine one again ran like a small well tuned sewing machine.
Notes to self....
Sometimes an obvious component failure is only coincidental to the actual mechanical problem.
Brass is not a very good choice of metal if you've underestimated the stresses it will have to handle.
These little machines know many more ways to make you feel foolish than you can ever possibly anticipate.
Steve
