How to check for a bent crankshaft?
03-18-2012, 07:02 PM
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How to check for a bent crankshaft?
I picked up a used os 1.60 at a swap meet this weekend, it has been in a crash and missing some cooling fins. I was kinda worryed that the crank might have a very slight bend in it as it vibrated like crazy today while on the runup stand, I got a what I think is a great deal on it but now im seeing why? I only paid 50.00 for it and it looks brand new. If I have to buy a new crank then I think Im still ahead? I think?
03-19-2012, 07:26 AM
#2
RE: How to check for a bent crankshaft?
Here is the crankshaft page: http://www3.towerhobbies.com/cgi-bin...?&I=LXUT06&P=Z
Tower lists it for $75.99, so you would have $126 invested in the engine if this is all that is damaged.
Tower lists it for $75.99, so you would have $126 invested in the engine if this is all that is damaged.
03-19-2012, 07:41 AM
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RE: How to check for a bent crankshaft?
There was a contact here on RCU that would straighten bent cranks for free. I have no experience with him, but might be worth a try. Do a search on bent cranks and it should pop up. If not I may have the link somewhere. Good luck.
03-19-2012, 07:46 AM
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RE: How to check for a bent crankshaft?
I'm sure a runout gauge would be best, but a crude method that I've used is to immobilize the engine - In my case I gently clamped it in my vice. I then positioned a pushrod to almost touch the center "dimple" of the crankshaft end. Rotate crankshaft and observe for deviance from center. In my particular crashed engine a bent crank was obvious.
03-19-2012, 07:50 AM
#6
RE: How to check for a bent crankshaft?
ORIGINAL: jknox
I'm sure a runout gauge would be best, but a crude method that I've used is to immobilize the engine - In my case I gently clamped it in my vice. I then positioned a pushrod to almost touch the center ''dimple'' of the crankshaft end. Rotate crankshaft and observe for deviance from center. In my particular crashed engine a bent crank was obvious.
A nice dial indicator is available from Harbor Freight, sometimes for as little as $9.99. A magnetic mount is also avail. FWIW.
03-19-2012, 08:07 AM
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RE: How to check for a bent crankshaft?
Thank you spaceworm, I sent Dave a question on his post I hope he responds and can fix it, Im worryed I may have caused more damage to it trying to remove it from the case.
03-19-2012, 11:44 AM
#8
RE: How to check for a bent crankshaft?
Here is a couple of videos on how to replace the bearings,. it also shows you how to remove the crankshaft too.
http://www.rcmodelreviews.com/bearings.shtml
One can simply affix the engine to something so it is still, so that you can rotate the crank and not have everything move in the process. Then you affix a nail or something so that the point is almost touching the tip of the crankshaft. You then turn the crank and see if it moves too much in reference to the nail point. Usually you can bolt on a prop to help make it easier as you are mainly interested in the tip runout. I don't remember anyone having a crank bent in the middle that still had little to no runout at the tip yet.
http://www.rcmodelreviews.com/bearings.shtml
One can simply affix the engine to something so it is still, so that you can rotate the crank and not have everything move in the process. Then you affix a nail or something so that the point is almost touching the tip of the crankshaft. You then turn the crank and see if it moves too much in reference to the nail point. Usually you can bolt on a prop to help make it easier as you are mainly interested in the tip runout. I don't remember anyone having a crank bent in the middle that still had little to no runout at the tip yet.
