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  #71  
Old 12-01-2022, 11:07 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
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Quote:
Originally Posted by KeithO View Post
If the shafts were then moved out of alignment I have not yet come up with a method that favors 1 pin, all of the pins should in turn have been overloaded as the pair of drive flanges rotated through the offset distance.
Just a sketch to illustrate the above, something I was playing with to satisfy my own curiosity. Agree with Keith; non-concentric rotation should load and unload the three ears equally, in turn, at first order. Note the change of length between the driving/driven pin pair given 180 degrees of rotation.
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RV-8 SS
Barrett IO-390
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  #72  
Old 12-01-2022, 11:44 AM
KeithO KeithO is offline
 
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Location: Jackson,MI
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Dan, so far the only scenario I have come up with is if the entire drive flange was offset to the shaft centerline. That would give you an offset distance that varies with the rotation angle. That could favor a single pin if the offset was towards that pin, so that the pin found itself at the greatest distance from the shaft centerline.

Jans video on fitting the drive flange to the gearbox seems to show a lot of difficulty to get it to go on straight and keep going on straight. The splines on the shaft also slice material out the inside of the drive flange, potentially making any shift permanent. Here is the link to that video:
https://youtu.be/gW0IyuERbcU?t=147

His assembly process seems geared toward creating exactly the type of defect that would cause this problem, be highly variable, and all down to human error because its all "eyeballed", If he actually used a dial indicator to validate that the radial distance of the pins was the same (so it was centered) that would at least be a check and balance. But no evidence of that at all.

Last edited by KeithO : 12-01-2022 at 11:47 AM.
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  #73  
Old 12-01-2022, 11:56 AM
KeithO KeithO is offline
 
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Well, I have news. I let the drive flange sit for hours since I did the inspection this morning and as it turns out there is indeed the start of a crack at a second drive ear. It took a long time to bleed out to the point that I could recognize it, so its probably very shallow still.

Interesting that it is not at the inboard end of the ear, its at the outboard end and tangential to the boss I mentioned earlier which holds the pin. The broken ear shows 2 different cracks, one outboard and 1 inboard. But the overall assumption is the same, far more damage to the ear that failed and damage now starting on one of the 2 remaining.
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  #74  
Old 12-01-2022, 02:26 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by KeithO View Post
Jans video on fitting the drive flange to the gearbox seems to show a lot of difficulty to get it to go on straight and keep going on straight....His assembly process seems geared toward creating exactly the type of defect that would cause this problem...
I especially like the part where he recommends hitting it with a hammer for alignment (about 3:35). The only place to hit it would be the ends of the lobes. Ack!

You're going to replace this thing with something better anyway. 100 lbs-ft nominal torque suggest a size 12. Replace the driving end with a flat disk (or better, integral, a new flywheel with a thickened center) drilled four places for Type S pins. Used a splined Type 1 slug on the driven side. If the existing splines are standard SAE, use a Type 1 L-LOC, which would allow slipping it onto the splines and clamping rather than using some variation of the press method. See attached.

Note the Centaflex A coupler places the rubber elements in compression when the radial fasteners are tightened. There are no tension fibers buried in the rubber.
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  #75  
Old 12-02-2022, 04:45 AM
KeithO KeithO is offline
 
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The barrier to experimentation right now is my ability to get some of the machined parts. I would have to reverse engineer the splined joint to be in a position to make my own input flange. From the discussion yesterday with Jan his gearbox supplier is legit with broaching, hobbing, heat treatment and gear shaving all in house. Part of the problem is that the 110 is one of the smallest engines in the lineup and its using a guibo that was designed for much more powerful engines. This makes the guibo "hard" for this application and it would for sure be better to use a product that has examples made for lower nominal torque values.

DanH I appreciate your recommendation and will try to educate myself more on the option that you raised. I do believe that a Civic manual transmission flywheel may fit onto the Fit crankshaft, they are available in CrMo with the starter teeth machined right into the billet flywheel, 1 less thing to go wrong. The flywheel would need to be lightened since its not accepting the thrust of a clutch plate, so the wear surface can be removed.
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  #76  
Old 12-02-2022, 09:52 AM
Tomcat RV4 Tomcat RV4 is offline
 
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Location: Jacksonville,Fl. 32246
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Same thing with Airtrikes out of Canada, bolts instead of pins, and NO CUT UP
BMW/MERCEDES rubber u joint, auto flywheel is lite, but factory made
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  #77  
Old 12-02-2022, 09:57 AM
Tomcat RV4 Tomcat RV4 is offline
 
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I am guessing (which is bad) that the only reason to cut up a BMW OR MERCEDES “ rubber donut” is if alignment is questionable on mating pieces
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  #78  
Old 12-02-2022, 12:40 PM
12vaitor 12vaitor is offline
 
Join Date: Aug 2012
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I was at the Work Boat Show in New Orleans yesterday and talked to several companies that specialize in TV dampers (Rexnord Centaflex-A, Geislinger, Timkin Lovejoy LF, Vulkan Megiflex-B, Renold HTB-MP, Isoflex, VibratechTVD). The guys at Vulkan had one of the best solutions for a 125 hp/6000 rpm engine-gearbox combination. Vulkan recommended using their Megiflex-B (similar to Centaflex-A and Lovejoy LF) with a split splined collar that would attach to the splines in the GB drive pinion shaft. The collar would clamp to the splined shaft with a cross bolt to close the split and prevent the collar from moving. The collar would have three threaded radial holes with 120 deg offsets for attaching the damper with hex socket bolts. The damper would be face bolted to the crankshaft side drive plate with hex bolts. Assembly would be similar to the current setup. The Vulkan folks said they would be happy to assist in the design, TV analysis, and manufacturing as desired (all the others likewise offered design assistance). The trick of course is finding and testing the correct Shore hardness for this application. The photo is the Centaflex-A version of the above.

OXE had a cutaway of their 300 hp Diesel outboard that uses a modified BMW turbo diesel engine for the powerhead. The TV coupler shown is on the business end, some type of molded plastic housing with puck style elastomers for light weight. Nice compact engine package designed to run all day at high rpm.

John Salak
RV-12 N896HS
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  #79  
Old 12-02-2022, 01:34 PM
KeithO KeithO is offline
 
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John, would you like to report back oh the price being asked for that 300hp outboard ?
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  #80  
Old 12-02-2022, 10:17 PM
12vaitor 12vaitor is offline
 
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Less than a new IO-540, but not by much. There is a reason the primary user market is government, military, and law enforcement. A 12-meter interceptor with 3 of these engines cost about the same as a house and will only do 54 knots on 900 hp. This is a well-engineered machine that has many millions of development dollars sunk into it.

John Salak
RV-12 N896HS
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