Prop keeps falling off
06-11-2008 | 09:24 PM
#1
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From: , PA
Prop keeps falling off
Twice now the prop has fallen off when starting my plane when I know for sure I put it on very tight. I have also very carefully balanced my propeller, so I do not think there is an unusual amount of vibration.
Anybody have any ideas what is causing this?
This is on a H9 Arrow with OS .55 AX
Anybody have any ideas what is causing this?
This is on a H9 Arrow with OS .55 AX
06-11-2008 | 10:09 PM
#2
RE: Prop keeps falling off
How are you starting it?
I use a 6" adjustable Crescent wrench to tighten my prop nuts on my glow engines and they stay tight. Maybe 30 ft-pounds of torque as a guess.
I use a 6" adjustable Crescent wrench to tighten my prop nuts on my glow engines and they stay tight. Maybe 30 ft-pounds of torque as a guess.
06-11-2008 | 10:12 PM
#3
My Feedback: (8)
RE: Prop keeps falling off
I was told to crank my prop nut right down. I use a little crescent wrench, and grip the prop with a towel, and pull the two together.
Maybe it's really obvious, but it goes thrust washer (with grooves in it, part of engine), spinner back plate, prop, prop washer, prop nut, cone.
I have the 46AX and have no problems.
Maybe it's really obvious, but it goes thrust washer (with grooves in it, part of engine), spinner back plate, prop, prop washer, prop nut, cone.
I have the 46AX and have no problems.
06-11-2008 | 10:20 PM
#4
RE: Prop keeps falling off
Don't be afraid to put some torque on it. The crank threads and nut are hardened so they will take it. Also, is the engine backfiring or something to cause the prop to come loose? Make sure you follow the starting procedure in the manual.
06-11-2008 | 10:24 PM
#5
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From: Wichita,
KS
RE: Prop keeps falling off
also how long are you keeping the starter on the cone for?? If you dont manualy prime the engine and then hit the cone with the starter your just asking for it to break lose.
06-11-2008 | 10:35 PM
#6
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RE: Prop keeps falling off
If you are using a propeller made from a plastic material and a spinner it will happen often.You need to put a disk of sandpaper glued back to back between the spinner and the engine and then some between the prop and the spinner. The prblem now is that there isn't enough friction between them no matter how much you tigten the prop nut. Also, try using a box end wrench. You will save the prop nut that way when you apply the torque. If you switch to a wooden prop you will be doing yourself a favor. Dan.
06-12-2008 | 12:05 AM
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From: Benton,
IL
RE: Prop keeps falling off
Hi Graybeard, Sometimes a dry engine is very hard to turn over but once it is wet with fuel it gets a lot easier.
I sometimes use a washer made of sheetrock sand paper. It looks like a gritty screenwire and works real well . Some of the cheaper spinners I've used are so soft they sort of just mash out instead of allowing the prop to tighten.
Fred
I sometimes use a washer made of sheetrock sand paper. It looks like a gritty screenwire and works real well . Some of the cheaper spinners I've used are so soft they sort of just mash out instead of allowing the prop to tighten.
Fred
06-12-2008 | 04:46 AM
#10
RE: Prop keeps falling off
I think they are making a friction disk out of it. The sandpaper for sheetrock is more of an abrasive screen, I don't know how it would compress. I do use a box end combo wrench to tighten my props, and a glove or small towel to hold the prop while doing it and have been successful at tightening all my props properly.. They will take some real torque and not strip the threads.
06-12-2008 | 05:16 AM
#11
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RE: Prop keeps falling off
ORIGINAL: gaRCfield
I use a plastic spinner and prop and have no problems. Doesn't sand paper wear things down even faster?
I use a plastic spinner and prop and have no problems. Doesn't sand paper wear things down even faster?
Yeah, when it's used as sandpaper. When it's trapped between two things that've been tightened with a wrench, it's not a problem. Modelers have been using sandpaper washers forever. Probably longer than there have been cheap plastic spinner backplates.
06-12-2008 | 07:01 AM
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From: Cape Spencer,
NB, CANADA
RE: Prop keeps falling off
If you're starting with a chickenstick, this is commonly caused by over-priming. And like the others say, really tight. Those combo glowplug/prop wrench cross shaped things are not adequate for tightening a prop. Use a real wrench and draw the wrench and prop blade together, tight as you reasonably can.
J
J
06-12-2008 | 08:12 AM
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From: , PA
RE: Prop keeps falling off
Thanks for the ideas. I am going to try the sandpaper suggestion. I am using plastic spinner and plastic prop, which have very little friction.
I am quiet sure all the parts are on in the correct order.
It is falling off when we bump it with an electric starter and it fails to start. The engine stops and the prop flings off.
Would there be any harm in applying thread locker to the shaft? I was also thinking about installing a second prop nut on top of the first one?
I am quiet sure all the parts are on in the correct order.
It is falling off when we bump it with an electric starter and it fails to start. The engine stops and the prop flings off.
Would there be any harm in applying thread locker to the shaft? I was also thinking about installing a second prop nut on top of the first one?
06-12-2008 | 10:42 AM
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From: Poolesville, MD
RE: Prop keeps falling off
Actually something that is being overlooked:
If your prop nut is "bottoming out", then it may not be exerting enough force to hold the prop in place, and as a result will work loose during start up.
Make sure that with the prop assembly in place the nut has plenty of available threads to go into when tightening down.
With a thin prop, on some engines, a shim or washer may be required to buy you the space to lock the prop nut down tightly.
If your prop nut is "bottoming out", then it may not be exerting enough force to hold the prop in place, and as a result will work loose during start up.
Make sure that with the prop assembly in place the nut has plenty of available threads to go into when tightening down.
With a thin prop, on some engines, a shim or washer may be required to buy you the space to lock the prop nut down tightly.
06-12-2008 | 11:11 AM
#16
My Feedback: (5)
RE: Prop keeps falling off
astrodad,
what kind of prop are you using ? you didnt by chance grab an E-prop did you ? they are thinner and wont work for a glow engines . other than that i would have no idea why it wont stay on. i have never had any props come off.
any chance you can post a pic of your set-up ? that would help alot.
bassman
P.S. there is no need to 'bump' the starter onto the spinner, just move the prop back to the beginning stroke and push the starter over the spinner and then push the button. i have never understood why people bump the starter on (have seen some do so hard) [:'(] all thats needed is a gentle but firm push to keep it on the spinner and start the engine.
what kind of prop are you using ? you didnt by chance grab an E-prop did you ? they are thinner and wont work for a glow engines . other than that i would have no idea why it wont stay on. i have never had any props come off.
any chance you can post a pic of your set-up ? that would help alot.
bassman
P.S. there is no need to 'bump' the starter onto the spinner, just move the prop back to the beginning stroke and push the starter over the spinner and then push the button. i have never understood why people bump the starter on (have seen some do so hard) [:'(] all thats needed is a gentle but firm push to keep it on the spinner and start the engine.
06-12-2008 | 11:32 AM
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From: Lexington,
KY
RE: Prop keeps falling off
ORIGINAL: bassmanh
astrodad,
what kind of prop are you using ? you didnt by chance grab an E-prop did you ? they are thinner and wont work for a glow engines . other than that i would have no idea why it wont stay on. i have never had any props come off.
any chance you can post a pic of your set-up ? that would help alot.
bassman
P.S. there is no need to 'bump' the starter onto the spinner, just move the prop back to the beginning stroke and push the starter over the spinner and then push the button. i have never understood why people bump the starter on (have seen some do so hard) [:'(] all thats needed is a gentle but firm push to keep it on the spinner and start the engine.
astrodad,
what kind of prop are you using ? you didnt by chance grab an E-prop did you ? they are thinner and wont work for a glow engines . other than that i would have no idea why it wont stay on. i have never had any props come off.
any chance you can post a pic of your set-up ? that would help alot.
bassman
P.S. there is no need to 'bump' the starter onto the spinner, just move the prop back to the beginning stroke and push the starter over the spinner and then push the button. i have never understood why people bump the starter on (have seen some do so hard) [:'(] all thats needed is a gentle but firm push to keep it on the spinner and start the engine.
06-12-2008 | 11:51 AM
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From: Chesnee,
SC
RE: Prop keeps falling off
ORIGINAL: Charlie P.
I use a 6" adjustable Crescent wrench ..................Maybe 30 ft-pounds of torque as a guess.
I use a 6" adjustable Crescent wrench ..................Maybe 30 ft-pounds of torque as a guess.
06-12-2008 | 09:35 PM
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From: Wichita,
KS
RE: Prop keeps falling off
ORIGINAL: Gray Beard
Turdfergerson, What is it about not priming my engine before hitting it with my starter that would cause me problems with my prop falling off??
Turdfergerson, What is it about not priming my engine before hitting it with my starter that would cause me problems with my prop falling off??
Like someone mentioned in another post, trying to turn a dry motor can create friction, making vibration that will cause the nut to back itself off. I had the same prob when I was first getting started in this hobby. before you apply the electric starter hold your finger over the exhaust outlet and turn the prop counter clockwise. wait until you can see fuel pass through the needle valve and up to the carb. then apply the glow stick and then the starter. if you find yourself turning the engine for more than five seconds remove the glow stick and reprime. it should only take a quick turn of the starter and she should fire up. good luck man.
06-13-2008 | 12:54 PM
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From: , PA
RE: Prop keeps falling off
ORIGINAL: bassmanh
astro,
glad its working for you now.
what was the solution ? let us know so others can use this thread for help.
bassman
astro,
glad its working for you now.
what was the solution ? let us know so others can use this thread for help.bassman
the whole assembly is thick as the prop shaf so there is no room for a 2nd nut. I did not have any suitable sandpaper, but I intend to put the sandpaper disks in there next time I pick some up.
06-13-2008 | 01:06 PM
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From: Oklahoma City,
OK
RE: Prop keeps falling off
ORIGINAL: turdfergerson
Like someone mentioned in another post, trying to turn a dry motor can create friction, making vibration that will cause the nut to back itself off. I had the same prob when I was first getting started in this hobby. before you apply the electric starter hold your finger over the exhaust outlet and turn the prop counter clockwise. wait until you can see fuel pass through the needle valve and up to the carb. then apply the glow stick and then the starter. if you find yourself turning the engine for more than five seconds remove the glow stick and reprime. it should only take a quick turn of the starter and she should fire up. good luck man.
ORIGINAL: Gray Beard
Turdfergerson, What is it about not priming my engine before hitting it with my starter that would cause me problems with my prop falling off??
Turdfergerson, What is it about not priming my engine before hitting it with my starter that would cause me problems with my prop falling off??
Like someone mentioned in another post, trying to turn a dry motor can create friction, making vibration that will cause the nut to back itself off. I had the same prob when I was first getting started in this hobby. before you apply the electric starter hold your finger over the exhaust outlet and turn the prop counter clockwise. wait until you can see fuel pass through the needle valve and up to the carb. then apply the glow stick and then the starter. if you find yourself turning the engine for more than five seconds remove the glow stick and reprime. it should only take a quick turn of the starter and she should fire up. good luck man.
06-13-2008 | 01:07 PM
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From: Cape Spencer,
NB, CANADA
RE: Prop keeps falling off
No need for the sandpaper, it's a bandaid solution. The truely tight nut is the real answer.
The cut-outs touching the prop blade would not have influenced tightness of the prop, but may have eventually caused a blade failure, so good job on clearancing that.
Prop blades always flex alot when I'm tightening them down. It's one of the things I use to gauge "tight".
J
The cut-outs touching the prop blade would not have influenced tightness of the prop, but may have eventually caused a blade failure, so good job on clearancing that.
Prop blades always flex alot when I'm tightening them down. It's one of the things I use to gauge "tight".
J
