needle valve adjusment safety?
06-18-2014, 05:55 PM
#4
Senior Member
Join Date: Apr 2005
Location: goolwasa, AUSTRALIA
Posts: 1,680
Likes: 0
Received 0 Likes
on
0 Posts
See if a piece of fuel tubing etc. will fit over the needle . At least that will stop the screw driver slipping off the needle . Having said that I would turn the engine off . Seen to many hands missing bits of fingers . Makes me cringe when I see people hand starting their engines ( glow ) when they have a starter just sitting there , Whats up wit dat ? Cheers the pope
06-19-2014, 09:59 AM
#6
I never would even think about adjusting a Walbo while the engine is running on the ground. For one it's just plain dangerous. Secondly you really should be making adjustments based on what it is doing in flight and not on the ground. Cowl pressure variations and engine loadings are different and will affect the tune, not to mention that gassers don't cool very well while on the ground and you will end up setting the mixture to a higher then operational engine temp.I will usually start flying an engine at a setting I know is too rich and then gradually work up to optimal setting based on what is happening in flight. It takes longer but once set there is usually no need for further adjustments.
06-19-2014, 10:41 AM
#7
I never would even think about adjusting a Walbro while the engine is running on the ground. For one it's just plain dangerous. Secondly you really should be making adjustments based on what it is doing in flight and not on the ground. Cowl pressure variations and engine loadings are different and will affect the tune, not to mention that gassers don't cool very well while on the ground and you will end up setting the mixture to a higher then operational engine temp.I will usually start flying an engine at a setting I know is too rich and then gradually work up to optimal setting based on what is happening in flight. It takes longer but once set there is usually no need for further adjustments.
06-19-2014, 10:53 AM
#8
06-20-2014, 03:41 PM
#11
My Feedback: (12)
Join Date: Apr 2009
Location: Ann Arbor,
MI
Posts: 1,186
Likes: 0
Received 0 Likes
on
0 Posts
How so? The best way to adjust a glow engine is with the engine running and the needle valves on those engines are much closer to the prop than they are on rear carb gassers. In fact, the only time I injured myself was on a glow tri-motor. Sheer stupidity on my part caused it. On a rear carb gasser, the needles are a good 5" from the prop. Slide a piece of fuel tubing or carbon rod over each needle so that the rod sticks out of the cowl. Have a buddy hold the tail and work the radio. Be aware of your surroundings and adjust away. I certainly respect those of you that want to be extra safe, but I have never been hurt nor seen anyone hurt using this method.
06-20-2014, 03:47 PM
#12
I bought a RC engine several years ago that had a on-board adjustable hi speed needle that worked off a servo. That same thing could be done with a Walbro carb now. You should use a down link system to monitor the engine temp. Might work out good if done right.
Capt,n
Capt,n
06-20-2014, 04:13 PM
#13
How so? The best way to adjust a glow engine is with the engine running and the needle valves on those engines are much closer to the prop than they are on rear carb gassers. In fact, the only time I injured myself was on a glow tri-motor. Sheer stupidity on my part caused it. On a rear carb gasser, the needles are a good 5" from the prop. Slide a piece of fuel tubing or carbon rod over each needle so that the rod sticks out of the cowl. Have a buddy hold the tail and work the radio. Be aware of your surroundings and adjust away. I certainly respect those of you that want to be extra safe, but I have never been hurt nor seen anyone hurt using this's method.
06-20-2014, 06:21 PM
#14
My Feedback: (2)
Speed, others, I think this might be a subjective deal. My little Evo 10 with it's front carb bothers me more (regarding prop clearance) than anything I've run with a rear carb. That said, I'm assuming that the engine we're discussing is in a plane that is fairly secure on an elevated stand? Or, maybe a secure test stand?
If I were messing with something like you're talking about (w/30" prop), to adjust the carb while the engine is running, I may be laying on the ground next to it, with a 30" prop spinning inches from my head. That's a big no thank you from where I'm sitting!
An inexperienced tuner, trying to adjust his idle early in his gas engine experience, might not be as familiar as others regarding which way to go when adjusting, or how far to go. With this in mind, adjusting the carb while running might be much easier on him than asking him to shut it down each time? I would look at that as something that might get to be a little frustrating? Safe yes, but necessary? Maybe not. As has been suggested, especially when dealing with rear carb setups, there are ways to make adjustments with a reasonable degree of safety. Assuming proper safe guards are in place (like a secure plane on an elevated rack, maybe using the soda straw method or something similar), I think a carb can be adjusted safely - with the engine running.
Last thought, hopefully you aren't so ham fisted when adjusting your carb that you manage to engage the front of your prop. If you do manage to get a knuckle or something into lightly it while adjusting, it's not going to be in slice mode. It's going to be trying to push your knuckle back out of the way? Certainly not condoning the practice, it will put the fear of God back into you, but I don't think of it as being near as dangerous as getting near a tip or into the front of it. That's me though, FWIW. -Al
If I were messing with something like you're talking about (w/30" prop), to adjust the carb while the engine is running, I may be laying on the ground next to it, with a 30" prop spinning inches from my head. That's a big no thank you from where I'm sitting!
An inexperienced tuner, trying to adjust his idle early in his gas engine experience, might not be as familiar as others regarding which way to go when adjusting, or how far to go. With this in mind, adjusting the carb while running might be much easier on him than asking him to shut it down each time? I would look at that as something that might get to be a little frustrating? Safe yes, but necessary? Maybe not. As has been suggested, especially when dealing with rear carb setups, there are ways to make adjustments with a reasonable degree of safety. Assuming proper safe guards are in place (like a secure plane on an elevated rack, maybe using the soda straw method or something similar), I think a carb can be adjusted safely - with the engine running.
Last thought, hopefully you aren't so ham fisted when adjusting your carb that you manage to engage the front of your prop. If you do manage to get a knuckle or something into lightly it while adjusting, it's not going to be in slice mode. It's going to be trying to push your knuckle back out of the way? Certainly not condoning the practice, it will put the fear of God back into you, but I don't think of it as being near as dangerous as getting near a tip or into the front of it. That's me though, FWIW. -Al
Last edited by ahicks; 06-20-2014 at 06:23 PM.
06-20-2014, 06:53 PM
#15
My Feedback: (12)
Join Date: Apr 2009
Location: Ann Arbor,
MI
Posts: 1,186
Likes: 0
Received 0 Likes
on
0 Posts
For one, a glow engine does not vibrate nearly as much as a gasser. Glow engines are much more affected by the environmental conditions. Once set one usually does not need to continually adjust a gasser like you would a glow engine. Not to mention the prop size and prop weight some gassers are running. Just to show I practice what I preach, my newest gasser has been flown 6 flights between Wednesday and today. The cowl has come off 3 times to make a mixture adjustment and inspection of the engine/exhaust system. By the final flight today she was ripping the 30x12 Bolly. I think I'm going to need a bigger prop. LOL. I would never even consider trying to adjust this monster with it running.
First off: Nice aircraft!
Second, a Super Tigre 3250 can take off your hand just as easily as a 30cc gasser. Plus, they have needle valves that are 1" from the prop and your knuckles are 1/4" from the prop when turning that needle. I am much more careful and fearful of adjusting that carb than any gasser I have ever touched. Granted, I have never had an engine with the displacement that yours has on an airframe that won't fit on a flight stand. In that case, I don't blame you for being very wary of unforseen disasters. However, from my point of view, when adjusting an engine on an airframe that is secured on a flight stand and using some small, common sense precautions, I think it's a bit sensational to say that it is fundamentally unsafe and foolish to tune a gasser while running.
06-20-2014, 08:10 PM
#16
Thread Starter
Join Date: Jul 2012
Location: Fort Madison ,
IA
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
06-21-2014, 03:52 AM
#17
For one, a glow engine does not vibrate nearly as much as a gasser. Glow engines are much more affected by the environmental conditions. Once set one usually does not need to continually adjust a gasser like you would a glow engine. Not to mention the prop size and prop weight some gassers are running. Just to show I practice what I preach, my newest gasser has been flown 6 flights between Wednesday and today. The cowl has come off 3 times to make a mixture adjustment and inspection of the engine/exhaust system. By the final flight today she was ripping the 30x12 Bolly. I think I'm going to need a bigger prop. LOL. I would never even consider trying to adjust this monster with it running.
06-21-2014, 07:31 AM
#18
Al, you make good points. I honestly did not invision a smaller gasser on a stand. I agree that for a newbie to gas this may be a good way to familiarize with the different tuning charicteristics. I would probably still make a sour face should I see that happening though. This may come from having to to rush my father to the ER after he got his right hand mixed up with an APC 13x6 while tuning a Saito .72. He ended up requiring a couple reconstructive surgeries. After that I got maybe a little too cautious if there is such a thing. I still drop my glow engines down to idle before making adjustments to the high speed needle and obviously shut down my gassers.
06-21-2014, 12:09 PM
#19
My Feedback: (283)
Join Date: Oct 2002
Location: Madison, AL
Posts: 186
Likes: 0
Received 0 Likes
on
0 Posts
Stop the truck. Did I miss something. There is no mention of adjusting a Walbro carb or for that matter gas engine carb in the first post. He asked about the needle valve. As in glow engine. Glow engine isn't really mentioned either but the implication is there. The answer is very carefully. It is dangerous but modelers have been doing it since the beginning. Just be careful and from behind the engine and never reach around the prop. Make sure the model is held in place by a helper or on a stand. As for gas engines no way while The engine is running. Set the needled per MFG and lean or ritchen a little at a time till satisfied. it does not take very much adjustment for a gas engine from factory setings.
06-21-2014, 04:02 PM
#21
My Feedback: (2)
He asked the same question on another forum. Grosbeak posted a picture of his version of the soda straw method. Apparently that was the answer he was looking for as it generated a thank you.
Also apparently is that it was a good question as it generated a lot of thought here....
Also apparently is that it was a good question as it generated a lot of thought here....
06-21-2014, 07:07 PM
#22
http://www.amazon.com/Performance-To...adjusting+tool
Has anybody have used this?
Has anybody have used this?
06-22-2014, 08:38 AM
#23
I made my own carb adjusting tool years ago. Take the Hi speed needle out... solder on a head of a allen bolt on the very end. Then make a 'Tee handle about a foot long with the same size hex. Drill a small hole in cowl...and then you can adjust carb. Make sure someone holds plane or tie tail down to a good stake.
AV8TOR
06-22-2014, 03:16 PM
#25
Join Date: Oct 2002
Location: Lyndonville, VT
Posts: 3,305
Likes: 0
Received 0 Likes
on
0 Posts
I made my own carb adjusting tool years ago. Take the Hi speed needle out... solder on a head of a allen bolt on the very end. Then make a 'Tee handle about a foot long with the same size hex. Drill a small hole in cowl...and then you can adjust carb. Make sure someone holds plane or tie tail down to a good stake.
I also use two different size Allen heads. I use a 6-32 screw for the HS needle and a 4-40 for the LS needle. My ball drivers for those two sizes are clearly marked H & L on the handle.
I also use the 6-32 Allen head screw for the HS needle on my 4 stroke glow engines by simply drilling out the hole for the needle valve extension, then cut the 6-32 screw to fit and lock it with the set screw that's in the head of the normal glow HS needle. The ball driver allows angling the tool and my hand farther from the prop.
Pete