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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 519154 times)
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wobblywalrus
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« Reply #435 on: May 05, 2011, 09:03:03 PM »

Type "stress concentration" into Google or another search engine and all sorts of interesting material pops up.  It is good to be familiar with these concepts when it is time to inspect parts.  The primary purpose of examining parts is to spot problems before they become disasters and most distress occurs first where stress is concentrated.

This little piston has been through a lot of races.  First, I look at the skirt for cracks originating at the edges with emphasis on sharp corners or other discontinuities that concentrate stress.  These are often called stress risers.  This skirt is well designed and there no significant stress risers or cracks.

Next I look for cracks around the gudgeon pin bosses.  None there.  Then I carefully look at the skirt.  There is a very small hairline crack 2 to 3 mm long about a mm in front of the penciled arrow.  A glance at the back of the skirt shows why this area is susceptible to cracking.  These is an abrupt section change between the thin skirt and the thick reinforcing rib.  Stresses are concentrated here.  Mechanical loads may be the cause, or thermally induced stresses from repeated heating and cooling, or a combination of both.  It is time for a new piston. 


* Crack Yamaha.JPG (126.27 KB, 800x533 - viewed 145 times.)

* Skirt behind crack Yamaha.JPG (137.82 KB, 800x533 - viewed 156 times.)
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wobblywalrus
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« Reply #436 on: May 07, 2011, 09:59:59 PM »

Years ago there were no systems for monitoring or collecting engine data.  Racers used their senses such as hearing, sniffing, and feel; they looked at their results; and they examined their engine parts during tear downs.  One of my big regrets is not learning from them the finer points of seeing these indicators or remembering everything the old racers told me about them.  One indicator I remember to look at is the bottom of the piston crown, as follows.

uncolored - everything is cool, calm, and controlled in the combustion chamber
slight yellow orange and shiny - hotter than uncolored, not unusual
brown and shiny - hotter than yellow orange, not unusual for an air cooled race engine
black and shiny - hot in the combustion chamber, not unusual for a race motor but too hot for a street engine
black and dull - highly oxidized oil.  A very hot mama.  Trouble waiting to happen.

The little Yamaha piston is shown with its pin.  The crown is uncolored.  It is a cool runner.  The gudgeon pin also led a happy life.  Shiny and worn with no discoloration.  An amber color would indicate that it got hot and a blue color would say it got even hotter.  This helps me make tuning decisions.  The Yamaha can tolerate some performance enhancement without running too hot.

 

   


* Crown Color Yamaha.JPG (147.04 KB, 800x502 - viewed 135 times.)
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wobblywalrus
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« Reply #437 on: May 09, 2011, 12:13:17 AM »

One rocker arm adjustment screw end was pitted.  This indicates that the valve clearance was excessive and the valve was being slammed open and shut.  This stressed the valve train and I looked at all parts carefully.  This keeper has a what appears to be a horizontal crack in the conical hole about 2 mm below the top.  I have never seen a keeper crack in this location.  Needless to say, both keepers, both valves, and all four collets will be replaced, and I will pay more attention to keeping the valve clearances correct.   


* Keeper Crack Yamaha.JPG (146.05 KB, 800x533 - viewed 159 times.)

* Keper Crack 1 Yamaha.JPG (142.19 KB, 800x533 - viewed 147 times.)
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wobblywalrus
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« Reply #438 on: May 09, 2011, 11:22:31 PM »

The Triumph forks come apart in the typical fashion of Showa units.  The bolts on the bottom of the forks that hold the damping rods in place are removed along with the wire circlips that retain the fork seals.  The inner and outer tubes are repeatedly pulled apart like a slide hammer.  This loosens and pulls out the seals and outer fork bushings.  One of the seals was corroded in place.  It appeared that salt somehow got in there.  Imagine that.

It took a lot of violent slide hammering to separate the tubes.  The fork bushings got bunged up in the process.  The teflon coating was wearing off of them, too.  This is not good.  The bushings are steel with copper plating and a teflon coating.  The teflon keeps the steel bushings from wearing out the aluminum outer tubes and the polished steel inner tube.  New bushings are needed.

Truimph makes the outer bushings that are housed in the outer fork tube.  They do not supply the inner bushings.  The only supplier I could find for the inner bushings in GB or USA was Race Tech.  I ordered a set of dust seals, oil seals, outer fork bushings, and inner bushings from them.  Nothing they sent would fit the forks.  All was returned to them except the inner bushings.  I ordered Triumph parts and I will Mc Gyver the Race Tech lower bushings to fit.  These are split sleeve bushings as shown in the photo.  The original bushings will be used as a guide.

The part is blackened and some sharp divider calipers are set at a distance 0.5 mm wider than the original bushings.  The dividers are used to scribe a line around the longer bushing.  This method is useful when a line must be scribed that is parallel to a face.  See the picture.


* Split Bushings.JPG (183 KB, 800x430 - viewed 133 times.)

* Scribing Cut Line IMG_1961.JPG (148.54 KB, 800x533 - viewed 123 times.)
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wobblywalrus
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« Reply #439 on: May 10, 2011, 11:39:06 PM »

These bushings must fit tightly against the groove in the inner fork tube.  It is important to not trash the teflon coating or bend them during the next steps.  It is almost impossible to get them bent back to the correct shape.  The bushings are laid on a dowel and sawed to a length about 0.5 mm longer than the finished dimension.

The sawed bushings are sanded to the final length.  Coarse sandpaper is used first followed by finer grits.  I measure them periodically with my cheap dial calipers as I work them closer to the finished size.  It is possible to get them close to perfect with some patience.


 


* Circumcision.JPG (177.74 KB, 800x533 - viewed 233 times.)

* Sanding to Size.JPG (200.06 KB, 800x533 - viewed 129 times.)
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wobblywalrus
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« Reply #440 on: May 11, 2011, 11:57:42 PM »

The bushing is sanded to size and the rough sanded edge is smoothed with an oil stone.  The bushing is put on the new fork tube and the end gap is measured and compared to the gap in the old bushing on the old fork tube.  A line is scribed on the new bushing, it is removed, and a file is used to get the correct gap on the new bushing.

One trick I use is to file down close to the final surface using my eyes with no magnification.  Then I do the final filing under the magnification and light of the lamp I use for parts inspection.  This results in much more accurate work.

It is tempting to ignore this step and to leave the gap small.  Some fork oil is trapped between the inner and outer tubes.  This oil flows in and out of the gap when the fork is compressed or extended.  I always make the gap the same width as it was on the original tube and bushing.  This assures the oil flow will be correct.  About 2 or 3 mm needed to be trimmed from the new bushing to get the right gap. 


* Oil Escape Gaps.JPG (146.26 KB, 733x600 - viewed 133 times.)

* Filing the Gap.JPG (172.36 KB, 800x533 - viewed 231 times.)
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wobblywalrus
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« Reply #441 on: May 12, 2011, 11:39:56 PM »

The last step in the bushing project is the final fitting.  The bushing is put on the fork tube and the fork tube is clamped upside down in a vice.  Leather protects the tube from the jaws.  The outer tube is pushed on.  It is an interference fit.  The bushing is removed and the inside of the bushing is sanded.  The fit is checked again.  This procedure is repeated several times until the outer tube fits on the inner with a clearance fit.  The fit is checked on the other three bushings, too.  All bushings are tuned so they are barely large or small enough to provide a clearance fit.  Now it is time to put the fork together.

The fork will have thicker tubes and they fit in homemade triple clamps with 7 mm less offset than standard.  This has been a big project undertaken over several years and it has been a lot of work.  It is done to give the bike the stability and strength to carry a lot of sheet metal streamlining.  There is another way to do this.  Unfortunately for me, I learned about it last week.

The German company LSL makes triple clamps with 52 mm offset.  This is 3 mm less than the 55 mm Bonneville offset and 8 mm less than the 60 mm Thruxton offset.  This will give stability.  The LSL clamps are 200 mm wide.  This is 10 mm wider than the 190 mm standard clamps.  The LSL clamps can be made to accept the standard 41 mm fork tubes or stronger 43 mm tubes.  There is a picture of a brown tanked Triumph on their website www.clubman.de  It has the clamps.  The webpage is in German.  I contacted them in English by e-mail.  They promptly replied in English with answers to my questions.  Although I have not tried the LSL products, using their clamps with some bigger and stronger tubes makes a lot of sense.   


* Final Sizing.JPG (182.63 KB, 800x533 - viewed 128 times.)

* Gravity Moves it Down.JPG (148.6 KB, 800x533 - viewed 132 times.)
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wobblywalrus
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« Reply #442 on: May 14, 2011, 02:56:49 PM »

Any recommendations for a good quality satin black spray can motorcycle engine, head, and cylinder paint?  The brands I can find around here are Rustoleum, PJ-1, and VHT.  I could probably find more with minor effort.  I am looking for durability.  Cost is no big problem.
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wobblywalrus
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« Reply #443 on: May 22, 2011, 01:02:10 PM »

The engine paint I tried is satin black VHT "High Temperature Motorsport Case Paint."  It applied well and seems to be tough.  Long term durability is not known.

Any recommendations on a motorcycle engine machinist?  It is an air cooled two valve single cylinder engine.  Pretty basic.  The jobs are a simple cylinder rebore, reaming valve guides and a five angle valve job.  As is typical, I procrastinated on porting the head until time is running short and I need the work done in about three to four weeks.  A person with a good reputation for quick turn around is best.
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dadsolds
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« Reply #444 on: May 23, 2011, 01:04:58 PM »

I'd give Brent Faulkner at Hatch Engine in Aumsville a call at 503-769-7188. They've been around a long time, do aircraft, automotive, balancing, flowbench work and so on.
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wobblywalrus
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« Reply #445 on: May 26, 2011, 11:24:24 PM »

The head was heated to about 350 degrees in the oven and I pounded the old guides out.  It was a hard push.  Then I did the port work.  It is a lot easier working on those little ports if the guides are out.  More room for fingers and sandpaper, etc.  Then I put the new guides in the icebox and heated the head to 350 degrees again.  I pounded them in with a brass drift.  It was a hard drive and I cracked both guides at the tops where the seals fit on.  I ordered a new pair.  How hot can a head be heated?  The oven goes up to 500 degrees.  I have gone up to 400 degrees a few times years ago but not more.  Any advice on how to install the guides? 


* Guides in Icebox.JPG (188.91 KB, 800x533 - viewed 124 times.)

* Head in Oven.JPG (230.45 KB, 800x533 - viewed 117 times.)
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Peter Jack
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« Reply #446 on: May 26, 2011, 11:34:47 PM »

When we were changing the bearings in the old Hewland gearboxes we usually used about 450 degrees. At that temperature the bearings would pretty much fall in or out.

I would probably build a stepped driver similar to a bushing driver to do the job.

Hope these suggestions help. They're based on my own experiences, others will certainly vary.

Pete
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wobblywalrus
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« Reply #447 on: May 26, 2011, 11:48:56 PM »

Thanks, Peter.  You are right.  A snug fitting and properly sized guide driver would evenly distribute the load across the valve guide top.  My drift sometimes did not hit square and it concentrated the impact on one part of the top edge.  More heat will help.

This seems like a good job for the machinist who will be boring the jug and cutting the valve seats.  He can quickly make up a proper driver if he does not have one.   
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wobblywalrus
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« Reply #448 on: June 04, 2011, 12:13:19 AM »

A few posts about the humble retaining ring.  There was a broken one laying at the bottom of the engine when I took it apart.  It was used to retain a spinning or sliding component on a shaft.  An external retaining ring fits in a groove around a shaft and it was one of those that let go.

Right now I am looking at the broken ring.  Where it came from is immaterial at this time.  The goal is to look at the ring and read its story.  Its condition will tell me a lot.

First, I look for wear.  A worn ring that has lost a lot of metal is weak and easy to dislodge or break.  The ring to the right in the first picture has lost a lot of metal.  It was replaced during a periodic inspection before it failed.  My broken ring has very little wear.  This is not the failure cause.

Second, I look for discoloration or signs of heat.  Is the ring annealed by heat and easy to bend?  An overheated ring that has lost its temper is weak and easily dislodged.  My broken ring does not show signs of overheating.

Third, I look for distortion such as necking near the break or bending.  This would indicate a sudden load stretched the ring through elastic and plastic deformation until it finally was pulled apart.  The parts of my ring are not bent or stretched.  There is no necking near the break.  Nothing indicates it was pulled apart.

Fourth, was the ring put on the shaft backwards?  These rings are stamped from steel plate.  There is a face with a rounded edge and the other face has a sharp and square edge.  The loads on the ring should push the sharp edge toward the side of the groove on the shaft.  The wear marks tell the story.  The wear mark on the sharp face should be at the inside edge of the ring.  This is the reaction wear mark.  The ring to the left in the first picture shows a wear mark on the inside of the sharp face, like it should.  The second picture shows the rounded sides of two rings.  The wear marks are on the high points in the middle of the rings.  These are from the spinning gears and they are the load wear marks.  The loads are being applied to the correct faces on these two examples.  My broken ring was installed correctly.

Fifth, the process of elimination indicates that my ring was not worn out, broken from some sort of massive load, overheated, or installed backwards.  Metal fatigue from a cyclic load was the failure cause.  The engine shafts and other parts will be examined in the next post. 



* Rings 1.JPG (145.51 KB, 632x480 - viewed 136 times.)

* Rings 2.JPG (150.62 KB, 640x475 - viewed 132 times.)
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wobblywalrus
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« Reply #449 on: June 05, 2011, 12:22:48 AM »

The broken ring is shown in the first picture.  The engine is broken down and cleaned and the broken ring fit on the kick starter shaft.  The groove is worn and the edge carrying the load is rounded.  This part must be tossed.  The new retaining ring will not have adequate support.  A new shaft and the original equipment Yamaha retaining ring is ordered.  They arrive and the shaft is measured.  The outside diameter is 16.89 mm, the groove inside diameter is 15.95 mm, and the groove is 1.22 mm wide.

"external retaining ring" is typed into a computer search engine.  There are many charts on the manufacturer's websites with application charts.  It is easy to determine this is a 17 mm nominal diameter shaft and the groove is cut for a standard duty shaft ring.

 


* Busted Clip.JPG (143.92 KB, 640x427 - viewed 120 times.)

* Worn Groove.JPG (82.75 KB, 404x361 - viewed 123 times.)

* New and Old.JPG (145.79 KB, 640x427 - viewed 131 times.)
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