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Engine basics => Engine set up tips => Topic started by: frank mccune on March 28, 2020, 04:35:49 PM
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Hello All:
Whenever I tighten the prop nut, my engine, it becomes very tight and difficult to turn. The engine is a HP .40 Silver Star. I have 6 other HP .40 engines that I have, do not do this. What is wrong? I can not see any difference in the way that these engines are assembled.
Suggestions/comments?
Tia,
Frank McCune
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Hello All:
Whenever I tighten the prop nut, my engine, it becomes very tight and difficult to turn. The engine is a HP .40 Silver Star. I have 6 other HP .40 engines that I have, do not do this. What is wrong? I can not see any difference in the way that these engines are assembled.
Suggestions/comments?
Tia,
Frank McCune
Frank
you have a bearing that is not in properly, or not seated, OR you have a collet on the front that is not pushed all the way back to touch the inside race of the front bearing, most likely 1 of the 2
Randy
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Yes the HP-40's used to have some .4 or .5mm thick brass washer behind the front ball bearing.
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Hello All:
Whenever I tighten the prop nut, my engine, it becomes very tight and difficult to turn. The engine is a HP .40 Silver Star. I have 6 other HP .40 engines that I have, do not do this. What is wrong? I can not see any difference in the way that these engines are assembled.
Suggestions/comments?
Tia,
Frank McCune
Is this engine recently, just put back together ?
Randy
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Agreeing W/Randy about the botched collet syndrome, I've improperly done this .
John L.
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Hello All:
Thanks to all of those who replied!
After a night’s rest, I made the following observations:
The p&c still have a great seal.
I do not know if this engine was recently assembled as I received it with an unknown history
I pulled the prop driver off three other HP 40 engines and I noticed that the front bearing is recessed about 030” in the case. The problem engine has the front bearing flush with the case. Perhaps it is time to pull the front bearing to determine why the bearing is not fully seating.
I “found” a steel shim that will fit over the crankshaft and inside of the case It is about 030” thick. Does this belong in the bearing assembly If so, where
How does one remove the crankshaft and bearings from the front housing of this engine
Tia,
Frank McCune
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Others will give advise on removing front bearing. I have done this several times by heating the front of the crankcase with a propane torch. Then when the crankcase is expanded, pull the bearing out with a piece of piano wire bent with a hook at the end.
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Don't remove any bearings.
Put a prop on it, heat up the case to about "spit" hot, and while it is still hot tap on the end of the crank shaft with a mallet to seat the front bearing.
Tighten up the prop again, repeat as required.
You can also tap on the back of the crankshaft to seat the rear bearing. Works better if the rod has been removed.
I have various little delrin tools that fit in the case and have a hole in them to clear the crank pin to make this easier.
I made mine after I saw Henry Nelson install the bearings in one of my N15RV this way.
If this all fails then you might be missing the spacer that was previously mentioned.
I know ideally you would press on the outer races to install both front and rear bearings, but without special tools you do what you can.
Pressing from the inner races this way can (and probably does) lead to damage to balls and races, but in my experience this is not an issue.
(flame suit on :) )
Pat MacKenzie
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I got it back together and it appears to be correct as there is no drag or noise from the bearings. I left the spacer, shim, out as it appeared to prevent it from working correctly. I will test it on a test stand to determine how well it runs.
Next test is to compare the HP engines against the LA .40 and .46 engines. I have seen the OS engines run, and they run very well!
Thanks for all of the help,
Frank McCune
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Some of the PAW diesels have this problem and it mentions it in the insructions.
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Hi Again:
I just had the same experience after fitting new bearings into the same engine. Everything appeared to fit, but when I removed the split brass collet, I found that it was very tight on the crank. I placed a X acto glade in the split to open it a bit and reassembled the front end and all was well again. Perhaps I applied excessive torque when tightening the prop. I have no idea if one can over tighten the prop.
Suggestions / comments
Be well,
Frankly
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Do those engines have a spacer behind the front bearing like a SuperTigre?
We referred to that part as the forget-me-not.
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Read the second to last paragraph of this test of a Gold Cup.
http://sceptreflight.com/Model%20Engine%20Tests/HP%2040F%20Gold%20Cup.html
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Hi Brian:
Thanks for the info. Thus far, I have not seen any shims for the HP engines. I will continue to look for them.
The slit collet intrigues me as it appeared to be slightly flared on the larger end. This may be an indication that the thrust washer may have been forced too far to the rear. If this were the case, I doubt that a shim would have served a useful purpose.
Be well,
Frank
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Read the second to last paragraph of this test of a Gold Cup.
http://sceptreflight.com/Model%20Engine%20Tests/HP%2040F%20Gold%20Cup.html
I had the same thing happen with a PA61. I found a spare split cone drive that was cut slightly shallower, no problem.
Brett
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Hi Brian:
Thanks for the info. Thus far, I have not seen any shims for the HP engines. I will continue to look for them.
The slit collet intrigues me as it appeared to be slightly flared on the larger end. This may be an indication that the thrust washer may have been forced too far to the rear. If this were the case, I doubt that a shim would have served a useful purpose.
If so then the shim will provide the necessary clearance. It's pushes the entire collet forward, which is 1:1 with the clearance to the case.
Brett
p.s. by the way, reading back through this thread, I would caution everyone about doing anything to load the inner race of the bearing to either pull it out or push it in. If the press fit is on the outer race, you want to press on the outer race only. That keeps the balls and ball race out of the load path. I see several suggestions about pushing the bearing from the inner race above. If you do that because there's no other way (like to get it out from pushing from behind), then, assume it is damaged and replace it. A bearing is cheap compared to losing an entire weekend at a contest after it fails, or collateral damage from a failure trying to work itself out the exhaust.
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p.s. by the way, reading back through this thread, I would caution everyone about doing anything to load the inner race of the bearing to either pull it out or push it in. If the press fit is on the outer race, you want to press on the outer race only. That keeps the balls and ball race out of the load path. I see several suggestions about pushing the bearing from the inner race above. If you do that because there's no other way (like to get it out from pushing from behind), then, assume it is damaged and replace it. A bearing is cheap compared to losing an entire weekend at a contest after it fails, or collateral damage from a failure trying to work itself out the exhaust.
Yup. I haven't screwed up bearings this way on airplane motors, but I've screwed them up this way in other applications. Putting too much side force on a ball bearing just makes little ball-shaped dimples in the races, and that makes the bearing bumpy. Really, disastrously, badly bumpy.