flybyjohn

My Feedback: (2)

I have a tower hobbies 46 bb engine that has approximately 1/2 gallon of fuel through it. It crashed into the water last year at a float fly and the engine was completely cleaned out and oiled up with atf. I mounted the engine on a new uproar with floats to fly this year and started it up. It has the rear needle valve (never could seem to get them running right). It seemed to sound ok and but the pickup from idle to full throttle was quite slow. I had to hold the engine nose high or pinch the fuel line to get it to transition to full rpm's and once it was at full rpm's it would run fine, until it returned to idle again. I got the low end needle leaned out to where it was running ok and I put it away for the night. The next day I refueled it and started it up again and after a minute or two, I started hearing a loud knocking when it was running. you could hear it really good when at idle or when going from full throttle down to idle. The engine is mounted at 90 degrees if that makes any difference. I am using 15% nitro with synthetic caster blend with an additional little bit of caster added to it to bring the oil content from 18% up to about 21%. I am using a well balanced 11x6 ma scimitar prop. The engine still has a very tight pinch at the top of the stroke.

Does anyone know what the loud knocking sound could be from? It was so bad, I took it off the plane and bolted up a 52 I had laying around.

Sport_Pilot

Not sure which Tower engine you have, but the older bushed engines knock like that as do most bushed engines. If not then check for loose parts, back plate, needle, bearing housing, or engine to motor mount. Did you switch to a higher nitro fuel, or put the wrong fuel in the tank? If so the knock may be detonation.

flybyjohn

My Feedback: (2)

Fuel was the same from day to day. The engine is the ball bearing engine, serial number was 060 I think, maybe 030. I will check later today. Everything was tight on the engine. This knock was very loud, probably louder than when a tight abc engine is turned over by hand and you hear that clank sound of the piston getting stuck and unstuck in the top of the cylinder. but it was continuous as it was running, knock, knock, knock, knock....... and so on. I will try and get some video of the sound, that may help. It was definantly loudest when bringing it from full throttle to idle. At idle it just keeps knocking.

1QwkSport2.5r

If it were me, I'd be looking at the inside of the crankcase. Namely the conrod for excessive play. I'd be looking at the bearings and crankshaft too since they're right there.

wcmorrison

My Feedback: (2)

I would surmise it is knocking during unloading of the engine, as it is slowing down or at or near idle.  At wide open the prop is fully loaded trying to pull forward thus the crankshaft is full forward.  You might see marks on the inside of the back plate where the crankshaft is hittig the back plate.  It is common, as previously said, in the plain bearing engines, not so much so in the ball bearing engines.  Might be time to change out the bearings especially the aft main bearing.

I have several Tower Hobbies engines and found them all to be very good.  They are essentially the same as the old GMS series engines.  The muffler provided a sort of pipe effect allowing the engine to turn up a few hundred more RPMs than its cousins of the same capacity.  In fact, I often use the Tower Hobbies .46 muffler on an OS .46 or a Thunder Tiger Pro .46, it is an exact fit.  And it helps those engines to run a bit faster too.

RCPAUL

My Feedback: (1)

If you crashed into water, the engine may have ingested water causing hydrolic lock. This in turn may have bent the conrod, wrist pin or caused other damage. Check the internals carefully.

Mr Cox

Yes, better check the internals before running it any further.

A crash in water at full speed is not soft at all. Props will break and I've even bent a crank that way...

iskandar taib

My Feedback: (5)

Detonation in glow engines doesn't sound like knocking (i.e. hitting something with a hammer). It supposedly is more of a sizzling sound, "like eggs frying" is what a friend told me. Both of us are used to unmuffled engines, I'm not sure what you'd hear with a muffler attached. And as in cars, you'd expect it to occur at full throttle, not at idle.

Iskandar

Sport_Pilot

Only the small and high speed engines will sound like a frying egg. Most detonation cannot be heard, a bit more and it does not sound like a knock. A lot more and it can sound simillar to the rattle a bushed bearing engine makes, except it makes the sound at full speed not at or near idle.

flybyjohn

My Feedback: (2)

I took the engine apart and looked things over and all looked great. Put it back together and it would not make the sound immediately but after running it for about 5 minutes it started to do it again but only sometimes, and only when run at idle for about 30-45 sec. and then up to full throttle and then back to idle, I could hear it when returning to idle for a few seconds. It sounds almost like a card stuck in the propeller. Kind of like a bicycle card in a bike wheel. I have a video I shot of it but you can only hear the sound slightly at the end of the video right before the engine dies. It started right back up and sounds fine unless I do the sequence as stated above. It is not near as pronounced as it was the last time I ran it. It was a lot louder and happened during more of the throttle range around idle. I will post the video after I edit out all the unnecessary stuff.

flybyjohn

My Feedback: (2)

Ok, I don't know how to upload a video directly to this site but here is a link to youtube that shows the engine running. You can hear what I thought was a knock two times after returning from full throttle. It is not too loud in this video but was quite a bit louder the last time I ran it. [youtube]http://www.youtube.com/watch?v=PgeHWxyAvdM&feature=youtu.be[/youtube]

ok,,, looks like it got it now

Sport_Pilot

Sounds more like a clicking noise than a knock. It has me stumped. Did you check that the connecting rod had good fit on both ends?

Did you remove the crank? There could be some debris between the crank and crankcase. It almost sounds like something clicking across the crankshaft port. Have you tried to raise the carb a bit before tightening the clinch bolt or set screws?

jaka

Hi!
First! get rid of all those long fuel/pressure lines! They are way to long!
Are you sure that engine has ball bearings?? All plain bearinged engines has a "klackering" noice at low rpm due to the crank shaft moving forwards and backwards at low RPM

1QwkSport2.5r

Better look closer. It's plainly obvious it's ballraced. See the bulge on the front housing??? Someone with your experience should notice that I would have thought. The noise I hear that engine make doesn't sound anything like the 'clack' you get from non ballraced engines.

To the OP: I'd suggest pulling the crankshaft and checking the conrod and the bearings. Sounds like a bad ball retainer?

ronwc

My Feedback: (404)

I don't believe anything wrong with the engine, it's just the crank moving back and forth, may be missing the thrust washer. Also keep in mind when you "dunk" an engine, take glowplug out, turn over for a few seconds, put glowplug back in and re-crank to completely clear out, no need to take apart.

1QwkSport2.5r

There should not be any crank movement in a ballraced engine, nor should it have a thrust washer. The OP said it was a BB engine even.

I wonder now if the rear bearing isn't completely seated. That could cause issues too. Just a thought.

ronwc

My Feedback: (404)

The key words there are "should not" be any crank movement, but that's what it sounds like. Still no big deal either way, I would run it.

Sport_Pilot

It did not sound like the bushed engine rattle of the crank going back and forth to me. But then a loose unseated bearing allowing the crank to go back and forth may sound different than a bushed engine. Or it was from distortion of the web, or my speakers, or whatever.

wcmorrison

My Feedback: (2)

I guess my ears are to old, I do not hear anything unusual.  I do note that the muffler is not the original configuration and the anodizing is faded.  So the engine is not new, in fact it is well used.  That means it is well broken in and may have loosen up a bit.  It also means the bearings may have begun to go.  Replacing bearings is a cheap fix and easy to do.  I would recommend it.  And if you can find an original GMS .47/Tower Hobbies .46 muffler get one, you will enjoy an addition 5 or 6 hundred RPM out of the engine.

I have a couple of them and one I have worn out one a long time ago.  I found them to be good engines.  The had a purple anodized head and nose collet.  The anodization fades with use - high temperature makes it fade.  And it was not such a super anodizing job.  The GMS version was a gold head, it seemed to hold up better.  They were basically the same engine, at least the used the same muffler.  Tower Hobbies eventually got the US rights to the engine from MECOA, the original importer of the GMS line.  Not long after than both engines disappeared off the market.  Either Tower Hobbies killed or the factory in China quit making them, does not matter, the results are the same - another brand name gone.

flybyjohn

My Feedback: (2)

wcmorrison, I know the engine looks old and I don't know what happened to the purple color but the engine has very little run time. My brother bought the engine for his airplane that he never learned how to fly. It was a carl goldberg falcon II. I have been the only one who ever started it or ran it. Back about 10 years ago, when brand new, we started it in the drive way and ran about 2 tanks through it and then took it to the field and I flew it about 3 flights. He never had the confidence to pick up the radio and give it a go. That is all the flights it got with wheels on it. I then put floats on it and flew it for about 10 more flights before the trainer switch on the radio malfuctioned with my son on the trainer box and it went into the lake. So it definently has less than a gallon of fuel through it. Like I said, I don't know what happened to the coloring on the head but it just really faded bad.

As for the muffler, I have the muffler for it but after taking the engine off the plane and replacing it with a 52 two stroke, I put the tower muffler on the 52 and didn't want to take it off to test run the 46, so the tower 46 got the old thunder tiger muffler for the test. The noise can only really be heard in this video in the very end but the other day, it was really clanking up a storm. I don't know what happened to the noise from one day to the next.

Turk1

Hi I have such noise on my engines time to time.Also I have a warped head engine (JBA 56F) given by a friend so stuck at piston/liner so I can say that noise coming from con rod but not important at all.I can say your engine has got some little warp by lake too.Dont pay attention at all .Use some castor oil in your fuel.

Mr Cox

Yes, it sounds like a sloppy conrod fit to me too. It would be good to check which end it is, and to see if it has been binding anywhere. If all looks good then one can just run it. Castor in the oil will give extra protection and since it is thicker some of the noise might go away too.

jaka

Hi!
Yeah! I noticed the bearing bulge up front but some engines (ie. .25) have that bulge but are still plain bearinged engines. That's why I asked!

flybyjohn

My Feedback: (2)

PROBLEM SOLVED!!!! Front bearing

I ordered a set of bearings and they arrived yesterday so I pulled out the old bearings and looky at what I found. I think this is what the problem was. The broken bit must have been inside making a bunch of racket one day and when I partially disassembled it, the bit must have fallen out some how and with the bearing inside the housing, I did not see the broken piece. Well the new bearings in and it didn't look like there was any damage to the housing. We will see how it runs tomorrow.

thailazer

Hey, that is quite a find! Surely could cause a variety of funny noises, some which might have been expensive ones later on! Thanks for the update!