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Electronic solutions to modifying glow engines of all sizes to gasoline

Old 09-01-2022, 01:20 AM
  #601  
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Very cool Chris. Curiosity has me wondering what it was calibrated against. ???
Old 09-01-2022, 02:08 AM
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Wow. Supercool!
Old 09-01-2022, 05:53 AM
  #603  
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Originally Posted by Glowgeek
Very cool Chris. Curiosity has me wondering what it was calibrated against. ???
Dead weigh - Fulcrum arm test Lonnie - using 1.0 lbs at 5 inches. Lock the "drive" and pull appropriate weight at the appropriate fulcrum and mark the result..

Being in Aviation "Quality Assurance" I spend far to much time discussing (arguing) with the regulating inspectors over torque wrench calibration - Its a real rabbit hole with no bottom - At some point you have to "trust a test" and that test usually involves an arm and a weight... Although most torque devices are pretty robust - they are mechanical.. If a device goes bad between calibrations issues arise. Some companies require test to be conducted pre and post use but then have had their "calibrating devices" go bad resulting in fleet wide groundings...
Old 09-01-2022, 09:45 AM
  #604  
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Originally Posted by 1967brutus
Not really... the shear forces will ALWAYS be on the threaded part. The shouldered part is resting flat against the inside of the bore, but the shearforces act on the exact spot where the bolt leaves the rod and enters the cap, and that exact location is by definition still threaded.
I know what you mean with the radial forces on the rods, but they should be relatively minor, since the largest lateral acceleration of the bigend is slightly after 90 deg before TDC and slightly before 90 deg after TDC, and that still is "rod territory" when it comes to the forces of the crankpin in the bigend bearing.
The inertial stretching forces IMHO are the only real problems: If those overstress the bolts, the cap will come loose from the rod, but it won't slip under the bolt heads, the cap will start to slide around on its mating face with the rod. These forces can be calculated fairly easily.
In all fairlness, if I take a look at what M2 bolts can hold in a helicopter rotorhead, I am not too worried.

But I do have always wondered why there is no torqueing instructions on these caps from OS or ASP.
To my amazement, there also are no instructions on that included with that V8 I am on the verge of assembling...
That would be the case if the shouldered portion stopped right at the threads in the big end, but if the shouldered portion recessed into the big end, and the hole fit was close tolerance, both in the end cap and big end, then the load would go on the shouldered portion... it can be done with the right fastener, just finding good quality shouldered cap screws, Mc Master Carr is usually my source for those types of fittings, but were dealing with very small screws... Sometimes I go down to the aircraft surplus store to find various bits and pieces.

What I did with the strut clevis ends... they are true "fork" clevises with a shouldered 3 mm cap screw, where the shouldered section passes all the way through both forks, as well as the fuselage attachment bracket in the middle... the loc-nut just secures the 3mm fastener, pinched up just enough to takeup any clearance between the fork and the bracket.
Old 09-01-2022, 11:31 AM
  #605  
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Originally Posted by Cat 1
What cheapskates do when they need a torque wrench for a single use... Calibrated before and after use and very repeatable...

That reminds me of the beam style inch pound bearing preload gauge.
Old 09-01-2022, 11:41 AM
  #606  
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Originally Posted by John_M_
........................What I did with the strut clevis ends... they are true "fork" clevises with a shouldered 3 mm cap screw, where the shouldered section passes all the way through both forks, as well as the fuselage attachment bracket in the middle... the loc-nut just secures the 3mm fastener, pinched up just enough to takeup any clearance between the fork and the bracket.
Got a pic of that setup? Sounds like something I would like to have in my arsenal when needed.
Old 09-01-2022, 01:31 PM
  #607  
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Default Believe it or not

Not to add any fuel to the fire but this is an interesting discussion. Here is my take.


Believe it or not in extremely heavily loaded tension bolt fastenings in aviation the bolt shank is rarely used to locate the fitting and as such the clean shank is not an issue. KingAir wing fittings are a fine example. A big inconel bolt is fitted in tension - hole is “sloppy” and threads of the bolt are present inside the inboard fitting. The bolts only job it to pull the two pieces together. The only locating is by the friction of the mating faces - helped by serrated faces and a soft washer between them . The bolt (and it’s nut) only apply tension. Some other applications have a locating sleeve or collar but they rarely use the bolt to locate.

Shear fastenings are another story. A Twin Otter wing bolt is in shear. Snug hole(with bushings) has shank completely through the hole. Washers are used to ensure nut can be snugged without bottoming on threads but it’s not tightened. Must be able to be turned.

the bigger king airs finally went to a shear bolt in the lower forward fittings in the later models but the majority that fly around have tension bolts. Doesn’t it make you want to fly in a king air knowing that a tension bolt holds the wing on!!!😁
Old 09-01-2022, 02:11 PM
  #608  
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On connecting rods ( big engines ) the shoulder under the head of the rod bolt is larger in dia than the shank and has a lite interference fit in the rod end cap and in the big end for locating / aligning the bearing end cap... some use a hollow / tube as the locating dowel with an interference fit between the cap and big end.

The piper cubs, the struts are used to set the washout at the wing tip, so both struts are either in tension or compression to twist the wing tip... the clevis bolts are a slip fit with very little discernible play.

On the H9 model, they use a flat spade end clevis, with a through cotter pin, a short piece of silicone fuel tube to take up any play, and a cotter clip to hold the pin from coming out.

This is what I came up with.
https://ibb.co/8D7wC7W
Old 09-01-2022, 06:30 PM
  #609  
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I think we could debate for days about the application of various fasteners - Ultimately they all must function too a certain design criteria (if properly designed).. Tension is just that - Tension.. Shear is a bit easier to understand (and to design for) - Shear and tension gets tricky as the interaction of forces is hard to predict.

Here is my thought - The reason these tiny 2mm fasteners survive is that they are not really loaded that heavily. I believe their Max loading would occur somewhere on the exhaust / intake stroke where they must stop the pistons upward travel and draw the new charge into the cylinder. On compression and power they are only along for the ride.. if this is indeed the case then that explains why keeping revs below a certain speed is the ticket to survival - At some point the deceleration loads would exceed their breaking strength.
Old 09-01-2022, 09:24 PM
  #610  
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On the big engines, the inertia forces acting on the piston / con rod assembly can be upwards to 1000+ pounds at 6000 rpm, depends on the weight of the assembly... thats not including the loads from the power stroke, just the reciprocating inertia forces acting on the piston / con rod as it changes direction at rpm... there are formulas for calculating those loads.

Those bronze rods in the OS / ASP 1.60 boxer, take their weight plus the weight of the piston, pin & ring and run the numbers... not surprised those 2 mm cap screws fail, especially if there is poor QC... the first series cast bronze rods in the OS, twisted at the beam, and the wrist pin bushing failed, and the cast aluminum rods fractured across the porosity imperfections in the casting... Not sure why they choose to use bronze billet for the latest version, other than for its bearing properties, they could have used 7075 billet, but I believe they choose bronze for simplicity.

Last edited by John_M_; 09-01-2022 at 09:26 PM.
Old 09-02-2022, 02:27 AM
  #611  
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Originally Posted by Cat 1
I think we could debate for days about the application of various fasteners - Ultimately they all must function too a certain design criteria (if properly designed).. Tension is just that - Tension.. Shear is a bit easier to understand (and to design for) - Shear and tension gets tricky as the interaction of forces is hard to predict.

Here is my thought - The reason these tiny 2mm fasteners survive is that they are not really loaded that heavily. I believe their Max loading would occur somewhere on the exhaust / intake stroke where they must stop the pistons upward travel and draw the new charge into the cylinder. On compression and power they are only along for the ride.. if this is indeed the case then that explains why keeping revs below a certain speed is the ticket to survival - At some point the deceleration loads would exceed their breaking strength.
That's my understanding as well. Max tensile loading on the caps bolts is during the "toss mode" at TDC of the exhaust stroke.

Max shear loading on the cap bolts would happen with a crank angle near 90° btdc and atdc, but only if the cap slides on the big end. I suspect the oil film pressure helps spread some of those forces from the cap to the big end i.e. at those crank angles the shear forces are not experienced solely within the cap.

Last edited by Glowgeek; 09-02-2022 at 02:48 AM.
Old 09-02-2022, 05:16 AM
  #612  
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Originally Posted by Cat 1
Not to add any fuel to the fire but this is an interesting discussion. Here is my take.


Believe it or not in extremely heavily loaded tension bolt fastenings in aviation the bolt shank is rarely used to locate the fitting and as such the clean shank is not an issue. KingAir wing fittings are a fine example. A big inconel bolt is fitted in tension - hole is “sloppy” and threads of the bolt are present inside the inboard fitting. The bolts only job it to pull the two pieces together. The only locating is by the friction of the mating faces - helped by serrated faces and a soft washer between them . The bolt (and it’s nut) only apply tension. Some other applications have a locating sleeve or collar but they rarely use the bolt to locate.

Shear fastenings are another story. A Twin Otter wing bolt is in shear. Snug hole(with bushings) has shank completely through the hole. Washers are used to ensure nut can be snugged without bottoming on threads but it’s not tightened. Must be able to be turned.

the bigger king airs finally went to a shear bolt in the lower forward fittings in the later models but the majority that fly around have tension bolts. Doesn’t it make you want to fly in a king air knowing that a tension bolt holds the wing on!!!😁
i once (actually twice) jumped out of a twin otter. by the way, i'm already using the 3d printer for stuff. last noght i printed a jig for gluing fins to my son's giant patriot rocket model. i can already see this tool being very useful.

Old 09-02-2022, 05:36 AM
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Originally Posted by Raleighcopter
i once (actually twice) jumped out of a twin otter................
Nice looking part Dave. That's a fair size rocket.

I had temporary duty in Greenland while in the USAF, flew around in Twin Otters north of the Artic Circle many times.

Landing on ice runways, in the dark, with very heavy crosswinds is terrifying.

Last edited by Glowgeek; 09-02-2022 at 05:51 AM.
Old 09-02-2022, 05:55 AM
  #614  
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Originally Posted by John_M_
That would be the case if the shouldered portion stopped right at the threads in the big end, but if the shouldered portion recessed into the big end, and the hole fit was close tolerance, both in the end cap and big end, then the load would go on the shouldered portion...
True... but I have never EVER seen it that way... In fact, most specialized big-end bolts I encounter have the shoulder turned down to within the core diameter of the thread, such that the bolt will NEVER be loaded on shearforces. Most engine designers seem to think they are meant to stretch and that way tie down the cap, and they secure the cap against movement by position pins or serrated faces.
I have never seen it the way you describe it, although I have no problems accepting that way would work.
Old 09-02-2022, 06:57 AM
  #615  
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Originally Posted by 1967brutus
True... but I have never EVER seen it that way... In fact, most specialized big-end bolts I encounter have the shoulder turned down to within the core diameter of the thread, such that the bolt will NEVER be loaded on shearforces. Most engine designers seem to think they are meant to stretch and that way tie down the cap, and they secure the cap against movement by position pins or serrated faces.
I have never seen it the way you describe it, although I have no problems accepting that way would work.
"In the bold"... Thats basically the method I described to use on the model rods... The rods we use on the 500ci engines are monster rods made from 7075 billlet, and the big end & end caps faces are machined with the deep alignment serrations... Rod bolts very in design, depends on the material the rods are made of... some are captured through bolted with a nut... the nut can either be on the end cap side, or on the big end frame side... forged 4130 rods will have a small frame design to keep the mass down, and through bolted, where the shoulder acts as the alignment dowel... the shoulder fits tight in the end cap and protrudes into the big end to key and align the end cap.... so the portion of the dowel shoulder that protrudes into the big end frame is a tight fit approx .250" in depth... the threaded portion of the bolt is a slip fit... once you have the end cap seated on the dowels you torque the nuts to spec..

I have not seen the rods used in those massive marine diesel engines... although I did take a tour on a large ship once, where there was an access door on the side of the engine block./ crankcase.
Old 09-02-2022, 08:10 AM
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Originally Posted by John_M_
I have not seen the rods used in those massive marine diesel engines... although I did take a tour on a large ship once, where there was an access door on the side of the engine block./ crankcase.
The big crosshead 2-stroke engines usually have threaded rods with a "waist", screwed in threaded holes in the rod, then the big end cap is placed, and the nuts are hand tightened after the threaded rods are being stretched to tension with hydraulic jacks.
The "smaller" fourstrokes usually have four bolts per cap, 2 on each side, serrated faces, and usually a slanted separation between rod and cap, so the piston can be pulled out through the liner with the rod attached. Tightening by "normal" torquewrench at around 150 to 200 kg/m. I have wricked my ribcage a couple of times tightening those on my own. It usually is a two man job (and those torquewrenches have about 2 metres of leverage) but sometimes you're on your own and the job needs doing. Or so I thought. Not my brightest moments...
Old 09-02-2022, 09:19 AM
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Originally Posted by 1967brutus
True... but I have never EVER seen it that way... In fact, most specialized big-end bolts I encounter have the shoulder turned down to within the core diameter of the thread, such that the bolt will NEVER be loaded on shearforces. Most engine designers seem to think they are meant to stretch and that way tie down the cap, and they secure the cap against movement by position pins or serrated faces.
I have never seen it the way you describe it, although I have no problems accepting that way would work.
Another method was used by Ford, "Cracked Rod" technology. The rod started out as one piece and then was broken apart (cracked) right in the center of the big end opening. That process produced a perfect fitting cap and rod once reassembled.
Old 09-02-2022, 09:33 AM
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Originally Posted by Glowgeek
Another method was used by Ford, "Cracked Rod" technology. The rod started out as one piece and then was broken apart (cracked) right in the center of the big end opening. That process produced a perfect fitting cap and rod once reassembled.
I have heard about that, but never seen it,
Old 09-02-2022, 09:59 AM
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Originally Posted by 1967brutus
The big crosshead 2-stroke engines usually have threaded rods with a "waist", screwed in threaded holes in the rod, then the big end cap is placed, and the nuts are hand tightened after the threaded rods are being stretched to tension with hydraulic jacks.
The "smaller" fourstrokes usually have four bolts per cap, 2 on each side, serrated faces, and usually a slanted separation between rod and cap, so the piston can be pulled out through the liner with the rod attached. Tightening by "normal" torquewrench at around 150 to 200 kg/m. I have wricked my ribcage a couple of times tightening those on my own. It usually is a two man job (and those torquewrenches have about 2 metres of leverage) but sometimes you're on your own and the job needs doing. Or so I thought. Not my brightest moments...
The 7075 billet rods, the big end is machined / sized to spec with the end cap bolts torque to yield because of the distortion in the rod around the torqued fasteners... those rods get thrown away after a couple heets, they are completely buggered.

Sounds like torque to yield... With the sleeved aluminum blocks, we use a torque plate which takes the place of the cylinder head with holes for each cylinder access for boring and honing each cylinder while the head bolts are under full tension, due to the block distortion around the torqued fasteners... done correctly, when the engine is finally assembled and the head bolt torqued to yield, the cylinders remain true.
Old 09-02-2022, 11:23 AM
  #620  
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Originally Posted by Glowgeek
Another method was used by Ford, "Cracked Rod" technology. The rod started out as one piece and then was broken apart (cracked) right in the center of the big end opening. That process produced a perfect fitting cap and rod once reassembled.

Ford, Chrysler and a few others have used "faractured joint" rods. They need to be very clean at assembly and handled carefully. Joint faces well protected.
Old 09-02-2022, 02:22 PM
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Originally Posted by Glowgeek
Another method was used by Ford, "Cracked Rod" technology. The rod started out as one piece and then was broken apart (cracked) right in the center of the big end opening. That process produced a perfect fitting cap and rod once reassembled.
Originally Posted by 1967brutus
I have heard about that, but never seen it,
Another marvelous idea from the ford engineers, considering the industry standard has been used for decades without issue, just another way of cutting manufacturing costs... but at least you can't mistakenly mix up the end caps.
Old 09-02-2022, 02:42 PM
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Thanks again Chris, it's a perfect fit.

I will let the JBweld on the two top threads cure before attempting to swage the bottom threads, just in case I have to tap the bottom threads a tiny bit more. I'll report on the swaging Sunday. I'm pumped!


Old 09-02-2022, 04:50 PM
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That came out nice... whats the reason for the jbweld?... I see the damaged cooling fin, and a filled in spot below the insert.
Old 09-02-2022, 05:33 PM
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Originally Posted by John_M_
That came out nice... whats the reason for the jbweld?... I see the damaged cooling fin, and a filled in spot below the insert.
The JBweld it to keep the insert from unthreading, just in case my tap catches on a chip. I may not even need to tap the insert any further, depends on how the swaging of the 2 bottom threads goes. It's also there to seal off cylinder pressure in the event that the swaging process does not create a gas tight seal.

The triangle shape below the glow plug is part of the cylinder casting. I have no idea of it's purpose.

The previous owner was a ham fisted bull in a china store. He probably attempted to force one of those beefy glow plug tools onto the glow plug. There is not room between the fins for a tool like that, or a nut driver. A thin walled Saito FG spark plug tool works fine. The sloppy attempt to JBweld the fin back in place was his doing as well.

Hey, what should I expect for $150?. The saving grace is that the engine is a very low run time specimen, likely less than 1 gl. burned.

Last edited by Glowgeek; 09-02-2022 at 05:45 PM.
Old 09-02-2022, 06:52 PM
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Originally Posted by Glowgeek
Thanks again Chris, it's a perfect fit.

I will let the JBweld on the two top threads cure before attempting to swage the bottom threads, just in case I have to tap the bottom threads a tiny bit more. I'll report on the swaging Sunday. I'm pumped!
Makes me smile Lonnie - Long distance machine fits are always a bit of a dart game.. so much easier when your holding the recipient part in your hand...

My boxer is going back together... Ignition parts showed up today so I have no excuses anymore as all parts are here - Started drawing the TBI for it ..



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