Advice please, engine problem

[briankizner]

I was flying today and experienced what for me is a new engine problem.
Particulars--engine-DLE 55, prop-Xoar 23-8, good flying conditions- 20 K wind, 10 degree C,
This was my first flight with the plane since November. I did check that screws and connections were tight but I must admit that I did not remove the spinner and check the prop bolts. I always use loctite on the screws. I did balance the prop on my old Dubro balancer a few months ago when I installed it.
Motor started easily, I let it warm up a minute on the ground, revved it up a few times to make sure everything was OK then took off. Everything was fine for about two minutes when I saw something fall off the airplane. I decided to land as soon as possible, and started a landing approach. Ten seconds later, while turning final, I saw two or mor parts detach from the plane. The motor stalled seconds later and I successfully completed a deadstick landing with no damage to the structure (I am so glad to have had so many deadsticks over the years with glow engines).
I was surprised to see that the spinner and prop were gone. I went for a walk and found the spinner (it was the first thing that detached from the plane. I did not find the prop but I think it had broken into two pieces when it came off. Closer inspection showed that the prop shaft was bent and that the four prop mounting bolts were sheared off. The spinner is missing its mounting screw and the carbon fiber is mangled, apparently from the prop spinning loosely in it. (see photos).
Here are my questions. Why did this happen and can the engine be repaired? If reparable, can I order parts and do it myself or should I send the motor to a professional?
Some possibilities- the prop was not well balanced. The prop bolts were too loose or too tight. engine backfire (I did not hear any backfire, it seemed to be running very well).

[beto9]

Maybe you lost one blade of the prop and that bent the shaft...:confused:

[Ronald Longtin]

Could the prop screws have come loose on one side throwing your balance out of whack?

Or could the screws have not been tightened sequentially skewing your prop?

The latter happens occasionally with car wheels.

[briankizner]

Thanks, Alberto. I did not think of that. That may well be what happened. The extreme imbalance after the prop breaks could certainly explain the broken bolts, bent shaft and broken spinner. The prop had no scratches or dents before the flight. If this is what happened, does anyone know if wood props (or, at leat those made by Xoar) have any history of manufacturing defects?

[briankizner]

Also a good possibility, Ronald. Is there a correct sequence for tightening and is a torque wrench a good idea? If so, how much torque on the bolts?

[Ronald Longtin]

With multiple screws the idea is to properly seat the prop first then torque each screw in succession until everything is tight. I do'nt know the torque figure but I'm certain whatever you feel is tight is fine. The sequence is essentially to go to the opposite side whenever possible.

Wood props are subject to break when wet such as on a floatplane...

[bob forest]

Hi Brian, well the same thing happened to me with my Edge 540 with a FPE 52cc. What it was, was the spinner came loose and broke the prop, then the engine goes crazy as it is now unbalance and almost shook my plane apart. the 7 or 8 seconds that all this happen before I realized from the noise of the shaking I cut off the engine, and landed dead stick. So in my case it was the spinner coming loose, so now I check the spinner almost every flight. Re the repairs, in my case sent it back to First Place Engines, and they repaired it for about 150 bucks, was worth it. Re could I do it myself, not me, but I am sure someone with the knowledge could do it. I like the idea that they test run it, and when I got it back, ran like a new engine.
Bob

[Sempai-mj]

These forums are priceless, lots of experience and wisdom.

[briankizner]

You're right, Sempaj. It's great having some smart people to lean on. Thanks for the replies. I will send it for repair. Bob, I think you nailed it. Probably, the spinner came off first. I found it in the area where I first saw something break and the plane continued to fly well, though with a slightly different sound, for 10 to 15 seconds until some other bits (The prop, backplate, and front washer, I think) broke off. I am sorry I didn't find the prop. If intact, I'd use it again. If not, it would be an indication of what went wrong.
By the way, I got some replies to the same questions on Flying giants. They say I should send it for repair and a thorough checkup. One fellow also mentioned that he felt the problem was the spinner because a carbon fibre backplate will compress resulting in loose bolts. The same fellow also said not to use Loctite (no reason given) and to use a torquewrench set at 80-90 lbs. Until I hear good reasons, I will continue to hand tighten and use Loctite.

[dhamultun]

Loctite acts as a lubricant, reducing the coefficient of friction, and could lead to over torquing the bolts. Fasteners usually have a dry torque and lubricated torque specification. Lubricated torque is typically about .75 x dry torque.

[dhamultun]

Also be sure to confirm the torque units. Was it in-lbs or ft-lbs? 80-90 ft-lbs is in the range if a typical tire lug nut torque.

[Sempai-mj]

Dwight explained to me awhile back about the screws that fasten the prop to the back-plate weaken and develop cracks over time with the heating and cooling off that occurs from use.
He told me they should be checked from time to time so they don't snap while the engine is running.
My limited input.

[briankizner]

Thanks, everyone. I repeat that it's great having this knowledge available. This hobby is a continuing learning experience. The fellows at Flying Giants who have had similar experiences have honed in on the carbon fibre spinner backplate. One guy says the carbon fibre is a bit soft and its compression reduces the torque on the screws. Another says the problem with a carbon backplate is that it softens with engine heat. A couple of others say that the carbon backplate surface is too slick and allows a bit of rotation. Solutions offered include using a spinner with a metal backplate (eg Tru-Turn) or roughening the carbon backplate with coarse sandpaper before installation.
As far as repair, one says it is fairly easy to change the shaft and drive washer while others recommend sending the motor for repair. I did write to the dealer I bought the engine from (Azure Hobbies in Ontario). From the pictures I sent, he thinks the problem should be not too hard for me to repair after he sends the correct parts. I will try to remove the damaged parts tonight- if it is not too much of a problem, I'll then order the parts. Otherwise, I'll ship it to Azure.
I will also order a few mounting bolts so that I can change them regularly. And new spinner, and new propellor (ouch, this hobby costs a few Argentine Pesos)
And, while I'm at it, maybe I'll get Hondasaki's new solar geothermal nuclear diesel propane power-takeoff generator to recharge my batteries in flight. I was thinking to get Hydro Quebec to bring in poles and wires to my field in Labrador, bit Newfoundlanders and Labradoreans get pretty touchy about anything related to Hydro Quebec.

[Kevin Rochon]

Good one Brian,


On the sand paper issue I use to have a problem with a slipping prop so what I did is cut a two round pieces of coarse sand paper and put double side self adhesive tape in between and installed it in between the prop and the back plate, didn't slip anymore:)

[loflyer2001]

Hello Brian. I own two DLEs there are nice copies of their American counterpart but quality wise there are not the same. Torquing values
should be used with discretion and if in doubt use good common sense
tightning. Example:- If you over tight the cylinder to the crankcase,
the crankcase will eventually develop cracks along the bolts area.
Use North American quality bolts. Always use metal backplate for
spinner. It is no big deal to replace the crank, if you want to replace the
bearings (they can be purchased locally) remove the seals facing inward
to ease lubrification. The crank is cheaper to buy then to have it straighten.
Wooden props do create less damage to your engine.

[briankizner]

Thanks, Kevin. I couldn't resist a gentle poke at the wide-ranging discussion going on in another part of this forum.
I will do the same with my next spinner. By the way, I tried to remove the shaft but I do not have a long enough socket to place over the shaft and engage the nut behind it. Even if I could engage the nut, I am not sure if I have the tools to stop movement of the crankcase without damaging it as I try to loosen the nut. Rather than borrow or buy tools to do work I am unsure about, I boxed the engine and will send it to Johnny Zhao at Azure Hobbies in Markham tomorrow. Johnny (I think the company is a one man operation) tells me he will make sure the motor runs properly before returning it. So I guess I will be flying my Tango, which I have been flying concurrently with the gasser, and my old coroplast combat MIG for a few weeks. I also have a Fazer which I occasionally fly as well as two other glow planes that are ready to fly if I decide to blow the dust off them and put them in the car so I can last a few weeks without the big Extra. I should add that, having purchased the plane, engine, and several accessories from Azure over the last two years, that it is always a pleasure doing business with him. He knows Pilot RC planes and DLE engines very well and gives good advice, reasonable prices, and quick shipping. Check out the website.

[briankizner]

Thnks, Guy. I guess you posted while I was answering Kevin.

[dhamultun]

Brian...I wish we had a "Like" button! :D

[RichR]

[QUOTE=)
And, while I'm at it, maybe I'll get Hondasaki's new solar geothermal nuclear diesel propane power-takeoff generator to recharge my batteries in flight. I was thinking to get Hydro Quebec to bring in poles and wires to my field in Labrador, bit Newfoundlanders and Labradoreans get pretty touchy about anything related to Hydro Quebec.[/QUOTE]

Congrats, you deserve an award for the smartest comment on this forum!

[Michael V]

Hello Brian

Contrary to what others are saying, I believe this all happened because of your prop. I have found when using a wood prop on my gas engines I can not cover the hub with a spinner. Wood props especially cheap Zoar prop crush over time and I needed to tighten the prop bolts often. I am currently using a MENZ prop on my 100cc plane, no spinner and I check prop bolts almost every flight.
I believe this is what happened, during the flight a prop bolt or two came free or broke knocking the spinner. As you continued the turning motor was to much for the other prop bolts they broke and this sent the prop off..

that`s my 2 cents

[Burning Head]

Is it safe to use a split washer betwin the two prop bolt I use on my DLE 20cc

[xed]

While they may look good, I generally tend to not use a spinner on a gas engine. You cannot easily test your bolts or visually inspect them.. They are right in your face with the spinner off, every time you start the engine so if in doubt, test them at the beginning of the day and particularly after you have flown at least once since putting the prop on.

[briankizner]

Good ideas. I have noticed the compression of the prop by the bolts as the washer in the front definitely leaves a dent in the hub. Sometimes it would be great to have an FPV setup which may well record the sequence of events in an incident like this one.

[Kevin Rochon]

Even though your sending your engine in here is my trick to getting around not having a deep socket. I made this when I had the ZDZ to remove the prop shaft and that socket is also the exact one I need for my spark plug on the DA.

I find the proper socket, by itself it goes through, so what I did is flatten two parallel sides on the grinder and now I can torque it or take it off with a Wescott adjustable wrench.