acdii

Wow. The forces on that fin trying to do a knife edge was something else. Once it went, the canards went next and POOF no more plane.

modeltronics

My Feedback: (27)

It is so hot here in this part of Texas I decided I needed an inside project since I don’t want to go flying when it’s over 100 outside. I’m building an LT-40. I’ve had a few suggestions of what engine to use. I decided I would start with a FA-50. I have 3 of them and got out the test stand to pick an engine. Two of them ran very well but one was down on power. All of them were tested with my low nitro fuel and I used the Saito black hot dog shaped muffler on all the engines. I used the same 12X6 on all of the engines.

Once back in the shop with the AC running full blast, I decided to open up the engine that seemed down on power. The bearings felt good but looked all gooked up. About an hour later I had the bearings changed with a new set and I changed the seal where the intake goes into the head. Next to give it another run.

The top end was great. This engine spun up better than the other two I tested. I had the low end still set a little rich. Here is where it gets really strange. At any throttle setting under 4000 RPM, it makes a knocking sound.

I opened the engine to look inside. The con rod feels good. There is no slop that I can feel in the bearings. I ran the engine again and it still does it. The knocking sounds had me so puzzled that I called Lonnie and let him hear it over the phone. One thought we talked about was a sticking valve. I pulled the valve covers and the valves move fine but just to be safe I oiled the valve stems with 3 in 1 oil.

Another run and it still does it at any throttle setting under 4K RPM. Anything above 4K and it sounds great. It will idle at 2K forever but it knocks. If I put my hand on the engine, I can feel the knocking.

Has anyone ever had this problem? What do I need to do to get rid of the knocking? This engine didn’t act this way until I changed the bearings.

Monty Python

OK gotcha, hope you caught it and threw it through a saito prop while bench running an engine.

ps Bruce, maybe the jet owner had a mouse problem. Lets hope it was onboard for the crash

the Wasp

My Feedback: (1)

Pete, the way I feel about spiders is "you kill 1 spider you kill a thousand spiders

as for the knocking Saito 50 what plug? try a different heat range.

Jim

Jesse Open

Pedro,

How does the front face of the rear cover look ?

How about the drive pin to cam drive gear fit?

modeltronics

My Feedback: (27)

The fromt face of the rear cover looks good.. It does not have the swirl marks like the crank could be rubbing on it.. I will have to check the drive pin to the cam drive grear. The plug is an Evolution FS plug from Horizon. Fuel was 3% nitro with 18% oil. Prop was a Dynathrust 12X6.

Glowgeek

Wouldn't hurt to try a new plug, easy enough. If the noise started with new bearings, there's your sign. I had a rattling problem with new RCbearings brand bearings on one of my Saitos years back. No problems yet with Boca. I'm confident you'll figure it out Pedro.

Jesse Open

Yep, check the easy stuff first. Bearings not fully seated can be an issue. A bit of marking is normal,next time inside you may want to be certain both of the cam thrust washers are present. A long shot, but a possible.
Like Lonnie said, you will find it.

modeltronics

My Feedback: (27)

I disassembled the engine. With the crank still in place I used a depth mike to get a measurement from the back side of the case to the crank shaft. I heated everything up and put it in an arbor press and pressed very hard. After it had all cooled, I made another measurement with the depth mike. The difference was .002”. I checked two other things. The cam drive gear has no slop. I checked the cam to make sure the two thrust washers were there, yes they are and they are the older plastic ones.

The engine is all back together and feels fine. It will be the weekend before I can test the engine again and report back. It’s 104 degrees out right now and I don’t feel like going out to run it in the heat.

Jesse Open

You probably nailed it by seating that rear bearing

the Wasp

My Feedback: (1)

well, to prove it was the bearing seating I hope he uses the same plug.

BTW; I saw it myself, but I can't find the video. John Wayne once said, "Saito? well Saito ant no Tomato"
Jim

modeltronics

My Feedback: (27)

I got the day off from my part time job at the CNC lathe shop. We have plenty of orders but now there is a problem getting materials to make parts. I can’t figure out this economy.

I pulled my test stand out this morning before it got blazing hot out. I ran three 6-ounce tanks through the 50 and it works fine. Gary, I think you are right that I re-seated the bearings. The strange thing is that I only got the crank shaft to move .002” further in. Yes Jim, I did use the same plug but I was ready to try another if I had the knocking problem again.

I would like to know mechanically what the knocking noise was. I still can not get a cause and effect worked out in my mind.

Jesse Open

Good job!

It was the failure for the installation to take up the internal clearance in the rear bearing. At low thrust loads the bearing internal running clearance is relaxed. The resulting crank movements hammer out that note you heard.
The rear bearing outer ring, by design should be fully seated in the bore. The front face of the crank should abut the inner race of that bearing.

FlyerInOKC

My Feedback: (6)

It's fairly simple, in the post WWII/Korea era newer overseas steel plants were built, expanded, and modernized in the following decades. Meanwhile instead of updating and replacing the US plants companies like Pittsburg and Steel X spent the money on giving short term dividends to shareholders and ever fattening salaries to management. US heavy steel consuming industries either purchased cheaper overseas steel or move their own manufacturing overseas. Then came computers and the internet that made it possible to use the "just in time" system of ordering raw materials, gone were the stockpiles manufacturers use to keep on hand and had tying capital. Again, shareholders got bigger dividends and executives got an even greater increase in compensation. Now COVID-19 comes along to throw a mammoth size monkey wrench into the system. COVID shut down entire cities and regions in China and still have all the major ports tied up in knots. This shut off cheap steel and other products. Chinese suppliers shutdown, went bankrupt, etc. slowing and in some cases outright stopping the flow of goods they export.

acdii

That pretty much sums it all up. Corporate greed killed US manufacturing. Instead of paying workers to keep them happy and give them a better than poverty wage (except for union workers, but that's another egg), they paid executives huge sums and bonus for making share holders happy. Workers meanwhile get laid off, manufacturing goes over seas, the US goes from a manufacturing giant to a do you want fries with that service system. Even with that, companies ship that over to India!

If you look at what the jobs here are today, few are manufacturing, and those are mainly done by machines run by a single person, the majority of jobs being office sit on your ass in front of a computer and talking on a phone, or waiting on people whether its in a restaurant or a box store. Jobs that require skilled workers are stymied because of a lack of skilled workers, because it requires actual work instead of typing on a keyboard all day. Latest report I heard today is a lack of mechanics now. If I could make what I make in IT, I would prefer to repair cars all day, at least I would be mobile and burning energy.

I currently have the bed off my F350 and replaced the cross members and welded in some repair panels to remove rust, then primed and herculined the bottom. Right now it is sitting in primer waiting on a wet sanding prior to painting, and I just finished painting the frame with chassis paint to ward off further rust. I enjoy it! Prior to that I had the front end completely torn down and rebuilt it. I am hoping to have the bed and bumpers done and back on the truck by Sunday.

modeltronics

My Feedback: (27)

Gary, I can imagine that in my mind. You are saying that the bearing was moving around, slapping the sides of the case at low rpm because it was not totally seated. This caused the knocking sound. What surprises me is that I only measured .002” difference in how deep the crank shaft was after I applied a bunch of pressure after heat with an arbor press. Next time I change bearings in an engine I am going to get an initial measurement from the back of the crank case to the back surface on the crank shaft. Then after the bearing change, I better have the same measurement. This is the only way I can think of to know for sure the rear bearing it totally seated and everything is in the right place.



Mike, the economy has me puzzled. What you say about the steel is correct. For a while when I ran out of .5” stock to make parts I changed the CNC lathe over to run .625” 2205 steel to make the same parts and a lot more chips. Doing this involves program changes. This isn’t the first time we have had material problems. I just talk to the owner and he is in northern Texas trying to get material. He told me to come in tomorrow morning. The shop has 3 employees. Two retired guys (one is me) and a kid that farms part time. So, we are all part time. It pays well and the owner is great to work for. He brings in ice cream bars several afternoons a week for a break. Here is another place I can not figure out the economy. The owner would like to find a younger person to learn everything in the shop and totally take it over for him. The learning curve on these CNC machines is hard. So, a new person coming in would have to be someone that wanted a long term, steady, good paying job in a good work environment. That person. right now cannot be found.

I work there for a different reason. I like the learning and the work. This is very different that what I did in my pre-retirement life. Without this part time job, I will stay up to 2 AM building airplanes and then I will get on the Ham radio to talk to friends in New Zeeland and Australia. That schedule doesn’t go over well with my wife. Also, the owner of this shop lets me machine engine parts for me and supplies me with free methanol for fuel from a 55-gallon drum of VP he is no longer using. I borrowed the depth micrometer from the shop for the above measurements. It can’t get better than that.

Jesse Open

That is pretty much how the powers to be wanted the situation remembered. Being involved during that time, I recall a bit they tend to dismiss or under report. Just as with so many other once thriving US operations, never under value the under-handed, dirty dealing that only a corrupt government can undertake. They are now ramping up to overdrive. They don't screw up like this by accident!

erieqc

If you find one they think it’s ok to smoke dope and do their drugs and these companies are starting to think it’s ok to. No regard for anyones safety and well being.

Jesse Open

Not that, The internal ball to races running clearances are affected by the positions of the bearings in their bores and along the shaft.
I will send you a book that explains how that works.

Jesse Open

Not that, The internal ball to races running clearances are affected by the positions of the bearings in their bores and along the shaft. Too much clearance and the shifting, changing reciprocating loads and end thrust can combine to cause that rattle at certain speeds.
I will send you a book that explains how bearing installation works.


Text any time if you want to chat on 20 Meters.

the Wasp

My Feedback: (1)

hey guys, check out this video, wow

1200SportsterRider

In the two stroke world the rattling is called crankshaft "pistoning". If the crankshaft is a floating fit in the inner bearing races the alternating pressure and partial vacuum pulses in the crankcase will cause the crankshaft to move in and out at low rpm. It never hurts anything. No reason it couldn't happen in a fourstroke with loose fitting crankshaft.

1200SportsterRider

This gentleman pictured is one of if not the last Tuskeegee Airman, James Shipley, James passed away a day or two ago. Pictured with him is my sister in law Janice who made and presented the Tuskeegee Airman Red Tail Quilt to James. He shed tears as he identified each plane pictured on the quilt. My brother and Janice were honored to have James and his wife Mildred as neighbors and friends.

Jesse Open

Dave,

Thanks for showing that. I actually heard about his passing on the radio as well. A fine man and a good life indeed. Absolutely beautiful quilt .

FlyerInOKC

My Feedback: (6)

We could need more men of his character these days!