Inverted Honda engine

Discussion in 'General Auto Conversion Discussion' started by Brian Clayton, Dec 18, 2013.

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  1. Jan 11, 2014 #161
    The LS engines do have the thrust bearing in the middle of the crank. There is less flexing of the crank this way. If you want some really good info on crankshafts go to Crankshaft Design, Materials, Loads and Manufacturing, by EPI Inc. Its some good reading material. It even has some info on single plane crankshafts.
     
  2. Jan 31, 2014 #162
    Brian, how is the Honda progressing?
     
  3. Jan 31, 2014 #163

    rv6ejguy

    rv6ejguy

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    The thrust bearing location probably has little to do with reliability on a DD aircraft application as we've seen successful conversions done on many engine types with varied TB locations- front or center. At the 65hp level you are probably looking at the highest thrust load being under 300 lbs.- completely insignificant for a crankshaft of this size. We have to remember that the thrust force on the crank is much higher than this with the clutch depressed- like triple.
     
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  4. Jan 31, 2014 #164

    Brian Clayton

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    Other than being tied up at work, I have been looking at adding a crank support bearing. I ordered some odds and ends to finish the crank cover/ oil pan and I just need to sit down and weld them up. In the evenings,I have also been working on a new cockpit floor for a Beech 18. No worries, I have not stopped on it, I just needed to work some things out. I am not a CAD guy, I mostly just work out problems in my head and the backs of napkins.

    I had thought about just getting it running without a extra support bearing, but if I decided to add one later, any testing I did would have to be redone with a new configuration. So, might as well do it now.
     
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  5. Feb 1, 2014 #165

    Brian Clayton

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    I would like to make a request. I can go ahead and admit that high end math makes my ears smoke. I am not even going to pretend that I know where to start or could even do the math to competently figure the gyroscopic load on crank snout. If someone is willing to help me with this, please PM me. Happy to post the end result, I just dont want the process to take up 40 pages (maybe start a different thread?). If not, I am just going to put the largest (diameter and width) bearing that will fit in the space given. :) It may not be the best way, but I am looking at a cont radial case that has been remachined for modern bearings and I think they will fit in the space I have available.
     
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  6. Feb 5, 2014 #166

    Brian Clayton

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    The wonderful world of reverse engineering. I am still looking at bearings, and waiting for some returned calls. Interesting things about rated bearing life....they are very short! In the meantime, I am hunting block blueprints and starting to measure the back of the block, to reverse engineer the hole layout around the rear seal. The first step in a support bearing.

    I got the part numbers on the bearings in a cont radial.....dynamic load rating of about 17,000 ftlbs. Of course, thats a 300 hp engine with a huge heavy prop, but its a idea of what to shoot for. Since I am limited on OD, so far I have been dynamic load limited on a single row bearing. A double row may work, that is some of the calls I am waiting on. So far the highest single row bearing has been about 7,500 lbs with a 4300 rpm limit in oil. I have considered a hydrostatic bearing, but I dont think a bolt on bearing support would be stable enough for that, plus the prop adapter would have to be 2 parts and surface ground. It would also take some doing to make it work with thrust loads, much easier to do with a ball bearing. The downside is bearing life. A pressure bearing would last the rebuild life of the engine. Ball Bearings.....well, run it till it quits. :) Kidding aside, I think they get about 800-1000 hours in the radials, when machined for the new style bearings.
     
  7. Feb 5, 2014 #167

    BBerson

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    Thousands of VW conversions are flying direct drive with a smaller main bearing at the prop hub. Why do you need anything more?
     
  8. Feb 5, 2014 #168

    Brian Clayton

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    I agree. 60 or 70 hp with a 6 lb wooden prop. Now take that same vw, crank it up to 80 or 90 hp or more and hang a heavy adjustable prop on it with a prop extension. Weight aside, its the difference in a aircraft engine and everything else.....a massive bearing right behind the prop.


    And those bearings in a radial, it has three. 2 next to each other on the prop side one at 17,000 lbs (also handles thrust loads) and the other at 15,000lbs. The rear bearing is also a 15,000 lb bearing. The 2 15,000lb "main" bearings float in bronze sleeves.
     
  9. Feb 5, 2014 #169

    Toobuilder

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    I had my gearbox engineers at work looking at my DD setup a year or so ago, and yep, the bearing was the main issue. You'd think you could just call up something from the auto parts store, but not if you expect it to provide any reasonable MTBF. That factor is what is driving me toward the good old Lycoming plain bearing for the output shaft.
     
  10. Feb 5, 2014 #170

    Brian Clayton

    Brian Clayton

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    No kidding. The problem I see is this. The prop adapter bolts on on the flywheel end. It would have to be ground and finish machined after it is put on the crank, to ensure that the assembly is straight from one end to the other (for a hydro bearing). That means probably re-indexing the crank, which removes my factory nitride. Suddenly a new crank is looking better, by the time you made all the parts and had it re-machined. It would be fine if I was going in the engine business. The other issue for me is attaching the new support housing. The way I figure now, I can attach it with 8 5/16 studs and put in at least 2 new dowel pins. This includes attaching it to the rear main cap. If I do a factory style bearing, I dont think the housing would stay rigid enough for that style bearing, even incorporating the rear main cap into the new housing. On a LS engine, I think you could make a pretty nice structure that bolts to the bellhousing pattern have a new bearing support. I think the crank and prop adapter would still be a issue though. The cost of extensive machine work and prop adapter parts vs a brand new billet crank that already has a prop hub machined on like a std aviation engine. The other issue is line boring the block and bearing support. Since the mains would be different diameter (LS VS LYC), you might have some issues getting everything straight, without some custom fixtures.

    All this said.....I am also trying to not make a mountain out of a molehill.....
     
  11. Feb 6, 2014 #171

    BBerson

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    I guess I am confused, doesn't your crank already have a prop hub type flange where the flywheel was attached?
    Just needs a spacer or prop extension.
     
  12. Feb 6, 2014 #172

    raven-rotor

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    Brian

    Got your PM about the dimensions for the Honda® block bolt pattern you are working on. Don't have anything for your engine. We have had to digitize with a coordinate table to get the dimensions you are after. Haven't found the auto makers to be very generous in giving away their hard earned tech data for free. Try getting some metallurgical specs. for the crankshaft alloy for example.

    Just my opinion, but I would just get this little guy up and running with the prop bolted directly to the crank. There are so many more pressing questions about other unknown elements of this engine conversion to tackle first. Cooling, (oil delivery, drainage, and circulation), prop resonance, mounting points, etc. are farther up the list in my experience. Fifth bearings didn't even happen in the Corvair engine to aircraft world (believe VW too) until they had numbers flying all over for years.

    Keep up the good work!

    Jeron
    Raven ReDrives Inc.
    303-440-6234
     
  13. Feb 6, 2014 #173

    TFF

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    Steve Wittman's drive.
     

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  14. Feb 6, 2014 #174
    Reply: I had thought about that solution on various engines, but decided that adding a bolt on adapter hub was probably the most cost effective way to proceed. I don't see any problem with using an adapter that has a splined center hole to accept a shaft which would then drive the propellor. The splines allow for some very minor tolerance impropriety in concentricity and expansion of components as temperature changes. I felt that hub should be very simple to have made, and having it finish ground while attached to the crankshaft should be easy. All of the direct drive components would be housed in a case that could be removed as an assembly and would be a bolt on. Getting the housing to bolt concentrically with the crankshaft would require a little effort the first time, but dowel pins would then insure accurate reinstallation any time in the future. Going the one piece crankshaft route was , from my perspective, more limiting and expensive than a simple adapter.
     
  15. Feb 6, 2014 #175

    Brian Clayton

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    I saw that when I first started looking at DD stuff. I can do that because Hondas dont have a removable bellhousing and some moron (me) cut off all of the bellhousing flange. I guess I could make a plate though and start with another block. Its a option. I dont know that it would have to be as long of a prop adapter though, is there are "rule of thumb" for that?
     
  16. Feb 6, 2014 #176

    Brian Clayton

    Brian Clayton

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    Yes, it has a nice symmetrical bolt pattern with a dowel on the crank face. I am just exploring adding a prop support bearing.
     
  17. Feb 6, 2014 #177

    Brian Clayton

    Brian Clayton

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    Thanks Jeron. I sort of figured that, never hurts to ask though. If it was one of the big 3 domestics, I have a "in" on some engine related things. Imports not. Just trying to save some time and aggravation.

    I has considered doing as you suggested, I just figured I would tackle this head on. Two things bother me about this engine. The multi piece floating 180deg thrust and the fairly narrow main bearings. I just think for this to be viable, it will have to have some sort of prop support and additional thrust bearing capability. If I go ahead and try to solve the bearing issue now, it would be a major step. I think.....I can do this fairly easily. Maybe....sort of... well..... I am having fun anyway.
     
  18. Feb 7, 2014 #178

    Brian Clayton

    Brian Clayton

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    I had a long reply to this, till my internet connection dropped and I lost it. Short version "I dont know". I think its a good idea.
     
  19. Feb 7, 2014 #179

    TFF

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    I think Wittman's thought was easy to make on a lathe and lots of old cheap props discarded for old standard shaft. Newer style flange would require a bearing that would be big enough to slip over one of the ends.
     
  20. Feb 7, 2014 #180

    Brian Clayton

    Brian Clayton

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    Probably so. I would consider it, if I could just bolt a bell on the end. I probably would just wait, since it would be a "bolt on" part.
     

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