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DLE 55 Crank Broke in Flight

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Old 07-31-2012, 11:01 AM
  #26
daveopam
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Default RE: DLE 55 Crank Broke in Flight

And if you were the only one that had one break there, the parts would be in stock.

David
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Old 08-01-2012, 06:19 AM
  #27
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Default RE: DLE 55 Crank Broke in Flight

David,
When I get my engine back is there anything I should do to prevent this from happening again?
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Old 08-01-2012, 07:16 AM
  #28
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Default RE: DLE 55 Crank Broke in Flight

Sorry there isn't a thing you can do about poor metalurgy. BTW I have at least 2or 3 cranks from the dle 55 engines here thats brand new. I couldn't use the cranks but wanted the rods and bearings from the assy.
No way in Heck can you apply enough pressure to the spinner bolt to ever to break the crank , now over tightening the hub bolt may have a bearing on things but I really don't think that was what the issue was. I agree with what w8ye said about the metalurgy being wrong, DLE dosen't make there cranks, there farmed in just like alot of the other parts of the engine are. I can see where they could get a batch of bad cranks or anything else for that matter. it's just that heat treatment is a little harder to spot than other items. I really doubt that DLE is going to do a hardness check on each crankshaft before assembly.
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Old 08-01-2012, 08:43 AM
  #29
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Default RE: DLE 55 Crank Broke in Flight

After hardening the part must be drawn back in a oven at 550 F for one hour. If this is not done you get stress cracks in fillets.

And that brings up a second problem and that is improper fillets cause stress concentrations and resulting fractures. Look at the crank at the point of fracture and observe that it broke where there was a sharp corner?
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Old 08-01-2012, 01:38 PM
  #30
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Default RE: DLE 55 Crank Broke in Flight

w8ye is much more of an expert than I will ever be, but to answer your question, there is nothing you can do. You said the prop was balanced and I doubt if the engine was in a crash, so all you can do is run it. There are too many of these out there for all of them to have this issue. More than likely it was from a bad batch.

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Old 08-02-2012, 06:31 AM
  #31
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Default RE: DLE 55 Crank Broke in Flight

Ok, thanks for all of the info. I just wanted to be sure that it wasn't something I could remedy easily.
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Old 10-16-2012, 09:21 AM
  #32
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Default RE: DLE 55 Crank Broke in Flight

Soooo, I got my warranty repaired engine back from Hobby Services in August. I sold my house in the middle of August and moved into a new one in the middle of September so flying was a low priority for me for a while. I finally got the engine remounted and went flying a couple weeks ago. Just to make sure that the prop was not the cause I installed a new balanced prop, but I used the same spinner. On the 4th flight of the day the exact same thing happened. In mid flight it began to run erratically. Knowing what was happening I immediately landed the plane and once again the spinner fell off onto the runway.

This is twice now that I have lucked out and been able to safely land my plane. I do not want to try my luck a third time. What could be causing this. Should I press Hobby Services for a new engine? Could there be anything in mysetup that could cause this or is it likely to be in the motor.
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Old 10-16-2012, 12:56 PM
  #33
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Default RE: DLE 55 Crank Broke in Flight

Did you balance the spinner and does it run true with no wobble?
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Old 10-16-2012, 03:51 PM
  #34
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Default RE: DLE 55 Crank Broke in Flight

Also, what kind of spinner is it? Brand, etc.
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Old 10-16-2012, 06:18 PM
  #35
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Default RE: DLE 55 Crank Broke in Flight

Some years ago, there was a guy in the glow forums with a new Saito 62 that kept breaking the exhaust pipe.

I bought the engine from him spinner and all.

The spinner was not relieved to fit the prop and was distorted and undoubtably wobbled.

I put the engine on a plane immediately and have run it for four years with the same exhaust pipe he sent with the engine and a different spinner.

It is no different from any other Saito 62 Golden Knight and does not vibrate.
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Old 10-17-2012, 06:42 AM
  #36
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Default RE: DLE 55 Crank Broke in Flight


Quote:
ORIGINAL: w8ye

After hardening the part must be drawn back in a oven at 550 F for one hour. If this is not done you get stress cracks in fillets.

And that brings up a second problem and that is improper fillets cause stress concentrations and resulting fractures. Look at the crank at the point of fracture and observe that it broke where there was a sharp corner?
A friend helpedme machine the DLE55 to remove weight. We've found that the aluminum casting is high quality and my machinist friend thinks that it sounded like aircraft grade during the machining process.

We also checked the shaft hardeness and found it to be fully case hardened.

I find it hard to believe that my 55 is alone in its material quality.....Nevertheless, this is the second shaft I've heard of that has broken right at the threads of the prop stud. It's got to be vibration induced. All of the things the WYE8 and others are saying about balance, etc , should be done to make certain balance is right.

If excess vibration continues, one should check the timing. I suspect retarded timing may be a hidden cause of excess vibes, and it's a cause that's easily overlooked.

Wealso changed the position of the Hall sensor to vertically down in my modified engine. This required cutting a new keyway on the prop drive hub, so making certain ofwhen the engine is fired is an important piece to this puzzle. One shouldn't have to cut a new keyway in his engine of course, but checking the spark pick up and moving the pick up a few degreesare straight forward if notsimple to actually do

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Old 10-29-2012, 07:11 AM
  #37
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Default RE: DLE 55 Crank Broke in Flight

I have a DLE 55 that broke a crankshaft at exactly the same place. It had very little radius in the shoulder. It was not under warranty.
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Old 11-27-2012, 06:42 AM
  #38
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Default RE: DLE 55 Crank Broke in Flight

Sorry to not reply back to this any sooner. My life has been crazy to say the least the past several weeks with the birth of my first three children.

To respond to the questions above. I checked the balance on the spinner, and it was fine. I do not know the make of it, but the spinner and prop were running true without any obvious vibrations. As I stated above the prop that was used during the ifrst failure was balanced, and even though it appeared fine I replaced it with a new balanced prop. I am by no means a small engine expert and messing with the timing on these motors is not something I have any experience with. I have wondered if there could be an issue with the tuning, but the engine runs smoothly and does not hiccup or backfire. I am at a loss.
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Old 11-29-2012, 05:31 AM
  #39
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Default RE: DLE 55 Crank Broke in Flight


Quote:
ORIGINAL: Flyin Beagle

Sorry to not reply back to this any sooner. My life has been crazy to say the least the past several weeks with the birth of my first three children.
Wait, what?Back to the engine in a moment. You had your first three children? Triplets or a wife and two girlfriends? In any case congratulations.

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Old 11-29-2012, 06:20 AM
  #40
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Default RE: DLE 55 Crank Broke in Flight


Quote:
ORIGINAL: zx32tt

I have a DLE 55 that broke a crankshaft at exactly the same place. It had very little radius in the shoulder. It was not under warranty.
Right there is why the cranks break...the corrrect radius is needed to prevent a crack from developing. Just about all modern engines will employ a radius where needed on crankshafts. Capt,n
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Old 12-03-2012, 09:30 AM
  #41
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Default RE: DLE 55 Crank Broke in Flight

That's right K-Bob, Three little girls. Dont think I am going to have much time for my planes over the coming months, But i am holding out hope for a little anyway.

Back to the engine. I shipped it back to hobby services last week so we will see what they find. I checked the spinner and it is a true turn and it is balanced.

I dont know what is worng. Maybe I am just unlucky.
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Old 12-03-2012, 09:57 AM
  #42
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Default RE: DLE 55 Crank Broke in Flight

Talk about luck. Two cranks and three girls all in one year. Go buy a lottery ticket. Dennis
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Old 12-03-2012, 01:48 PM
  #43
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Default RE: DLE 55 Crank Broke in Flight

I would call them and press them hard for a new engine.

Hobby Services are pretty good to their customers. Tell them after two identical failures, you have lost confidence in the engine and are afraid to put it back in and it is obvious that they can't find the problem. What is going to take, a crash, etc. Also, you have lost a good portion of the warranty period and flying season in downtime. Time to start with a fresh one.

Also, I would get a backup. Flying season is too short up here to be messing around with their delays.

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Old 12-03-2012, 01:50 PM
  #44
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Default RE: DLE 55 Crank Broke in Flight

I would call them and press them hard for a new engine.

Hobby Services are pretty good to their customers. Tell them after two identical failures, you have lost confidence in the engine and are afraid to put it back in and it is obvious that they can't find the problem. What is going to take, a crash, etc. Also, you have lost a good portion of the warranty period and flying season in downtime. Time to start with a fresh one.

Also, I would get a backup. Flying season is too short up here to be messing around with their delays.
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Old 12-04-2012, 07:18 AM
  #45
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Default RE: DLE 55 Crank Broke in Flight

I have 3 DLE 55 Crankshafts left over from my engine building days that I didn't use. I have been hanging on to them just in case one of my own crankshafts failed for some reason. Since they are not a direct replacement for the engines I made I really had no use for them at the time. And so far my own cranks has shown to hold up just fine, So I have no reason to hold on to them any longer if anyone is interested in one send me a PM.
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Old 12-27-2012, 01:54 PM
  #46
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Default RE: DLE 55 Crank Broke in Flight

I wanted to post a follow-up to the broken crank saga.

I received a brand spanking new engine from Hobby Services last week. I included a letter with the broken engine when I returned it to them explaining the problems and giving a timeline of the events. I asked them to please provide a new engine or extended warranty on the repaired motor as my warranty was expiring on 12-30-12 and I knew I would not get the opportunity to test the repair prior to the warranty period ending.

Hobby Services, Thank You for making this right. I appreciate the good customer support.

Now I just need to find a little time to mount and use the new engine.

Thanks
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Old 12-27-2012, 07:29 PM
  #47
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Default RE: DLE 55 Crank Broke in Flight

Good job. I felt that they would do that. In the past, they have been great to me.
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