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  #11  
Old 05-09-2022, 10:59 AM
Nashpdman Nashpdman is offline
 
Join Date: Sep 2020
Location: Nashville
Posts: 60
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Quote:
Originally Posted by rongawer View Post
I've built my own engine several times, and I applaud your venture in this. Aside from all the mystery and fear surrounding "aircraft engines", a Lycoming 540 is essentially an expensive, high quality lawn mower engine.

They're pretty simple to build, but do have a few key points I've documented in other threads, with key points being that you should have your components OH'd by reputable vendors to certified standards...IMO. Also it requires adhering to torque specs and assembly instructions - so get a copy of the Lycoming OH manual and read it until you understand it.

The hardest part in the build is putting the crankshaft into the case and joining both halves - significantly the checks and torques that go along with that, so that's a good time to have expert help. Other than that, it's just assembling, using proper torque and understanding how fasteners work.

Don't let the fears of others dissuade you from pursuing your dreams. Just be smart about it.

Also, there is a bunch of Service Bulletins, Instructions and Notices, all freely available for download from Lycoming - you need to get all of them and read them. Much like playing golf, building a good engine is done in the preparation and planning.

As for fasteners, Mandatory Service Bulletin 240W clearly states to replace all stressed bolts and fasteners at OH. Anything that has been torqued, especially cylinder hold down bolts, rod bolts and crankcase through bolts - have been stretched. As an experimental builder, you are not required to adhere to service bulletins, but common sense says it's a smart thing to do.

Lastly, don't skimp or cut corners on your engine - save money somewhere else on the airplane. You wouldn't bargain shop for heart surgeon, so don't get cheap on the heart of your airplane either.
Your "lawn mower" engine is spot on, these things are simple! I guess that's why we're still using them. Simple, reliable, heavy. I'll convert the fear aspect into respect and give due diligence. I have the OH manual downloaded and reading it now. What's the best place or method to find the "Service Bulletins, Instructions and Notices"? I'm direct on the fasteners. And no skimping on the engine/parts/machine work. Thanks for the advice!
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  #12  
Old 05-09-2022, 11:05 AM
Nashpdman Nashpdman is offline
 
Join Date: Sep 2020
Location: Nashville
Posts: 60
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Quote:
Originally Posted by rongawer View Post
I completely agree. I purchased a B&C LX60 for my main and their BC410-H for my gear driven backup. Two batteries and two alternators to keep that "heart" beating.

Separately, I have a brand new set of superior pistons and valve covers in the box; I'll make you a killer deal...
Pistons you say? See the pics, these are what's in the engine now. Not sure I need the valve covers.
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  #13  
Old 05-09-2022, 11:09 AM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
Posts: 900
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Quote:
Originally Posted by rongawer View Post

Anything that has been torqued, especially cylinder hold down bolts, rod bolts and crankcase through bolts - have been stretched....
Can you clarify? Of course they have been stretched. Are you stating beyond their elastic limit? If so, please elaborate.

Fasteners in this type of app fail due to under torque -> cycles. That should be the OP's larger related concern here.
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  #14  
Old 05-09-2022, 11:48 AM
lr172 lr172 is offline
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 7,718
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Quote:
Originally Posted by rongawer View Post
As for fasteners, Mandatory Service Bulletin 240W clearly states to replace all stressed bolts and fasteners at OH. Anything that has been torqued, especially cylinder hold down bolts, rod bolts and crankcase through bolts - have been stretched. As an experimental builder, you are not required to adhere to service bulletins, but common sense says it's a smart thing to do.
First, a lycoming does not have cyl hold down bolts. There are studs in the case and nuts are used to hold the cylinders on. No one replaces these at overhaul, nor does Lyc require it. Also, all bolts stretch when torqued and when done properly, this stretching does not reduce their rated load capacity, nor does a bolt that has been torqued more than once have a lower rating than a new one. Every engine that I have ever built has had the connecting rod bolts and main cap bolts/studs torqued at least twice - once for clearance measurement and then final assembly. The exception is specialized "torque to yield" bolts that are sometimes used for main caps, rods or head bolts. Those must be discarded after torquing, as they don't fully rebound after stretching and therefore cannot effectively be re-torqued. There are no torque to yield bolts on a Lyc engine.

If lycoming was concerned and wanted the through bolts replaced at overhaul, it would be on the mandatory list, along with the 40 other items.

Larry
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Last edited by lr172 : 05-09-2022 at 11:55 AM.
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  #15  
Old 05-10-2022, 07:33 PM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
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Quote:
Originally Posted by Freemasm View Post
Can you clarify? Of course they have been stretched. Are you stating beyond their elastic limit? If so, please elaborate.

Fasteners in this type of app fail due to under torque -> cycles. That should be the OP's larger related concern here.
I encourage you to read SB 240W; it's a good resource for what should be replaced at repair or overhaul. Elaboration below.

Quote:
Originally Posted by lr172 View Post
First, a lycoming does not have cyl hold down bolts. There are studs in the case and nuts are used to hold the cylinders on.
True, Lycoming crankcases have studs and nuts that "hold" the cylinder to the case. Although technically studs, the thru studs are commonly referred to as "thru bolts"; sorry to confuse you, however, they are all threaded fasteners, and that is what is at issue here.

Quote:
Originally Posted by lr172 View Post
No one replaces these at overhaul, nor does Lyc require it.
It sounds like you and others don't replace all fasteners at OH, but to say "no one replaces" is a big stretch. If you buy an overhauled engine from Lycoming, it will have all new fasteners. I encourage you to call them at 1-570-323-6181 to discuss this with them. I am aware of two reputable shops near me (Ly-Con and Victor) and neither reuse fasteners at OH. SB 240W does state to replace all "Stressed bolts and fasteners, such as:". The "such as:" indicates an example list, and is not inclusive. If you don't believe your thru studs and crankcase nuts have been stressed, so be it - it's your engine, but I would say they are stressed and should not reused. They are only holding the engine together...YMMV

I certainly replace all fasteners at OH; I don't see the point of saving what amounted to about $800 dollars on my last build, for what is a 50K+ critical investment.

Quote:
Originally Posted by lr172 View Post
Also, all bolts stretch when torqued and when done properly, this stretching does not reduce their rated load capacity, nor does a bolt that has been torqued more than once have a lower rating than a new one.
Larry
It is accurate that all bolts (and studs, as you previously made a point of) stretch when torqued, but it is not accurate that their full strength is not reduced. Each time a fastener is fully torqued, it stretches and some plastic deformation occurs - from tensile stretching, but there is also frictional abrasion of the threading itself. This is generally measured in micrometers, or 10,000's of an inch, but it is happening.

The purpose for the torque is to place pre-load on the fastener, which ensures the fastened joint is retained during the cyclic stresses, both thermal and mechanical, that the engine encounters while in operation. If you measure a stud, torque it to its peak yield strength, remove it and then measure it again with a high accuracy micrometer, you will find it has developed some permanent stretch. Over the life of an engine, this torque induced stress, combined with cyclic stress leads to metal fatigue, which can become significant. This is why replacing connecting rod bolts, which receive a tremendous amount of cycling stress - likely the most of any engine fastener, are high on the list to be replaced.

BTW, visually inspecting a fastener may indicate damaged threads, but it is not a viable indicator for stretch. Even more so, cyclic fatigue is the major concern, not the total stretch - and that's impossible to inspect visually without the destructive evaluation.

Reusing a fastener for another OH cycle exposes it to even greater fatigue. Continued fatigue does weaken the fastener and it becomes nearer its yield strength each cycle. You might get away with reusing the fastener, but each time you torque it, it will weaken and eventually fail due to exceeding yield strength. At the very least, the threading will have more than desired wear.

Another issue with fastener reuse is corrosion protection. Once used, the cadmium plating on a lycoming specified fastener will have that plating ablated. There are some folks that will measure and determine that a fastener is reusable, and then send them to one of several vendors that re-plate fasteners. My preference is to simply recycle the old ones and buy new fasteners for my engine.

Mike, none of this should distract you from performing your own engine build. However, I highly recommend you gather all of the fasteners from your core engine and place them in a nice container for reference, and future recycling, but take the IPC, along with the spreadsheet I sent you, then go to J & J Airparts and have fun.
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- RV10, N762G, Build in progress.
- Several others that are now just great memories for me.

Last edited by rongawer : 05-10-2022 at 07:42 PM.
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  #16  
Old 05-10-2022, 08:19 PM
Freemasm Freemasm is offline
 
Join Date: Nov 2017
Location: Orlando
Posts: 900
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Could launch into a long rebuttal but there's no need. There's enough word play applied in the previous post that will let most informed individuals make up their minds.

I will supply a couple of hints. If you torque any fastener so that's it's stressed to it's "peak yield strength", you've done it wrong. Any operational stress would take the material into its plastic region -> strain increases, stress decreases. Game over. Likewise, attempting to purposely strain harden a fastener to achieve desired properties via installation in these related applications would be an asinine recipe for disaster.

Last edited by Freemasm : 05-10-2022 at 08:36 PM.
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  #17  
Old 05-10-2022, 10:28 PM
KeithO KeithO is offline
 
Join Date: Jul 2010
Location: Jackson,MI
Posts: 109
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Im rebuilding a Cummins 5.9 right now, made of cast iron and people will spend $850 just for ARP cylinder head studs to hold the head on. Now Im not drag racing and trying to keep my engine build to less than $4000 so I wont be spending top $ on ARP studs.

But, air cooled alloy engines go through a very different heat/cool cycle and the long bolts/studs used are far more critical than the fasteners in my water cooled cummins diesel. Its also quite difficult to properly inspect fasteners for the onset of fatigue. Sometimes the length can be accurately measured and rejected based on elongation alone, but not always.

So I agree with Rongawer that one should bear in mind the replacement value of the engine as a complete unit before skimping on new fasteners. In that context $800 for new fasteners is like a set of snow tires on my vehicle in winter, cheap insurance.

If you read the Jabiru engine overhaul manual, they have a procedure to determine if case fretting has occurred (attributable through loss of fastener tension over time due to fatigue). One basically measures crankshaft rotational drag as is, then re-torques the case fasteners and re-measures the drag. If the difference is greater than some amount then this is evidence of case fretting and requires the case to be re-faced and line bored to get it back into spec.
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  #18  
Old 05-20-2022, 07:31 PM
Nashpdman Nashpdman is offline
 
Join Date: Sep 2020
Location: Nashville
Posts: 60
Default Cleaning question

Is it approved or accepted to media blast the outside of the cylinders? I want to prep them for alondine and paint. I assume "walnut" shell would be the appropriate media?
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  #19  
Old 05-20-2022, 09:42 PM
SonexGuy SonexGuy is offline
 
Join Date: Oct 2021
Location: Maynard, MA
Posts: 26
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If you go to Airventure you can attend two Lycoming demonstrations (by Lycoming employees): 1. How to take apart a Lycoming engine, and 2. How to assemble a Lycoming engine.

These demonstrations fill up FAST, and require you pre-register for them. They are VERY, VERY good introductions to the process, and they show you a number of the tricks they use.

Kitplanes also had a 4-part series by Paul Dye about his experience rebuilding a Lycoming.
https://www.kitplanes.com/following-...tep-at-a-time/
https://www.kitplanes.com/overhaulin...-own-lycoming/
https://www.kitplanes.com/the-art-of-assembly/
https://www.kitplanes.com/final-steps-to-flight/

https://www.kitplanes.com/paul-dye-n...ycoming-class/

https://www.kitplanes.com/parts-off-parts-on/

I built my AeroVee (VW) engine 8 years ago. I really like knowing that I know that engine inside and out, and if I need to fix it, I can. I had a prop strike 6 years ago. I got a new crank, new bearings, and a new prop hub (and prop). I took the engine apart in 2 evenings, and put it together in 2 evenings. It's flown without a hiccup since. Once you know the engine, it's not that difficult, though the Lycoming is more sensitive to proper assembly and torque than the VW.

So I plan to buy a run out engine when it's time, and rebuild it myself (with the assistance of a mentor). I'll send everything out that needs to be sent out and machined, and get new parts where required, but I really like the thought of building the engine myself, and not leaving it to someone else.
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  #20  
Old 05-21-2022, 12:29 AM
rongawer rongawer is offline
 
Join Date: Dec 2007
Location: Brentwood, CA
Posts: 971
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Quote:
Originally Posted by Nashpdman View Post
Is it approved or accepted to media blast the outside of the cylinders? I want to prep them for alondine and paint. I assume "walnut" shell would be the appropriate media?
You could do that, however aircraft paint stripper will do a great job with little effort. Might take a couple coats if the cylinders have been heavily painted, but works well with a pressure washer and no metal removed.
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- RV10, N762G, Build in progress.
- Several others that are now just great memories for me.
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