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Author Topic: Team Go Dog, Go! Modified Partial Streamliners  (Read 1015182 times)

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Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3555 on: March 07, 2020, 10:41:08 PM »
Rex needs to answer that one...

The bolts are prepared for measurement.  A central hole is drilled in the head to make it easier to drill for safety wire.  The hole is champhered after it is drilled.  The hole size and chamfer are deliberately sized to accommodate the measuring ball.  The ball is part of a micrometer anvil attachment kit made by Swiss Precision.

A dimple is made in the screwy end of the bolt.  It accommodates the pointy anvil attachment.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3556 on: March 07, 2020, 11:01:27 PM »
The anvil attachments are attached and ready to go.  An aluminum sample is drilled and threaded to resemble the wheel.  The bolt is screwed into it with the spacer in its grip.  My most accurate torque wrench is used to increase tension in increments.  The bolt length is measured at the start with no tension, measured at each increment, and remeasured with no tension at the end of the session.  An increase in untensioned bolt length says that the bolt has been tightened beyond its yield point.

The correction suggested by Interested Observer was made.  Previously posted calculations say the maximum preload force for the bolt is 4,640 pounds or 4.640 kips.  Deflection stretch vs force calculates to be 0.000835 inches per kip.  4.64 x 0.000835 = 0.0038 4 inches.  The test should be stopped before stretch reaches 0.0038 inches so as to make sure the bolt is not permanently stretched.


Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3557 on: March 07, 2020, 11:33:38 PM »
The threads in the aluminum wheel will strip before the bolt will break, is my guess, and the maximum allowable bolt preload is 2,240 pounds force.  This was previously posted.  This equates to 0.00187 inches bolt stretch.

A 0.64 safety factor was used to get the 2,240 pounds.  2,240 / 0.64 = 3,500 pounds.  It is expected the wheel threads will strip at this force.  This equals 0.00029 inches of stretch.   

Let's look at the results.  The stretch vs torque curve starts out at a flat and gentle slope.  This is typical.  The clamped pieces and bolt head are snuggling down together.  The curve gets steeper and is linear.  This is the elastic region where everything is stretching and there is no yielding.  It goes from 6 to 12 pound-feet of torque.  The maximum allowable preload is in this area.  It looks like 9 pound-feet of torque is needed.  The curve starts to flatten out after 12 pounds-feet of torque.  This is above 0.00029 inches stretch and it indicates that threads are yielding.

Note the small amount of torque needed to get clamping force with a ti bolt.  It would be much larger with a steel bolt.  That is because the titanium surface is very smooth and there is a low friction coefficient.

A second test was done to make sure the results are consistent.  It was made with another bolt and aluminum sample.  The confusion starts with it.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3558 on: March 08, 2020, 09:59:36 PM »
The first test used an unknown alloy for the sample with internal threads.  A second test was made on a piece of threaded 6061 T5611 alloy.  The internal threads stripped at a very low pulling force.  The bumps in the line on the graph are the threads breaking.  The first to go is the one nearest to the bolt head.  The second hump is the adjacent thread.

The proper tap drill is 6.70 mm diameter.  The next larger fractional size drill was used 'cause it seemed to be close enough.  The previous day's test was done on a hole tapped with a "G" size drill which is slightly smaller than 6.70 mm.  Methinks the larger tap drill did not provide adequate internal thread height and engagement area.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3559 on: March 09, 2020, 12:38:36 AM »
This is the third test with the smaller size "G" tap drill.  The threads start to strip at higher stretch values like they should.  The desired bolt stretch is 0.0019 and there is a reasonable safety margin beyond that.  The 0019 value was reached at 9 lbs-ft in the first test with the unknown aluminum alloy.  It was reached at 13 to 14 lbs-ft with the 6061 T6511 in the third test.

Some metal to metal friction coefficients are real sensitive to surface cleanliness and oxidation.  Often a thread lube makes the torque vs clamping force relationship more consistent.  A delayed setting threadlocker that has some thread lube properties might be what I need.  Permatex or Loctite surface insensitive blue threadlockers work OK but they set up within seconds with this ti-aluminum combination.  This prevents me from developing these curves for design purposes.  Any suggestions are welcome.     






     

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3560 on: March 09, 2020, 01:22:18 AM »
One of these thread sealants might work best for lubing the threads, curing and providing threadlocking, and filling the gap between the threads to prevent corrosion.  https://www.vibra-tite.com/wp-content/uploads/Vibra-Tite-Catalog.pdf 

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3561 on: March 09, 2020, 09:27:24 PM »
The titanium bolt in aluminum threads is problematic and hardly the desired way to attach a brake disc to a wheel.  Threaded inserts will be installed.  The internal threads are M8 x 1.25.  This is a coarse thread.  The outer threads should also be coarse M12 x 1.5.  They would need to be ordered in and I want to finish this danged wheel now.  So, my hand reached into the box on the store shelf and pulled out a box of M8x 1.25 inside with M12 x 1.25 outside threads.  These fine threads are not optimal but they should work.  The inserts are passivated stainless steel.

These solid wall inserts have been more reliable for me than the coil type.  Also, the outside threads are drilled and tapped with standard M12 x 1.25 items.  An old M8 x 1.25 bolt is the installation tool and drift punch is used to hammer down the four little keys.  No special tools are needed.  After installation a drop of wicking Loctite is used to seal behind the threads. 

https://www.hfsindustrial.com/keensert-solid-inserts.html

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3562 on: March 10, 2020, 01:09:06 PM »
The typical blue threadlocking liquids set up within seconds or minutes.  This is a big problem if there is a delay, like some adjustment is needed or other fasteners need to be installed before the final torquing.  Torque that is needed to overcome the locking compound resistance is not making clamping force.

The ideal threadlocker would work with inert metals like ti and stainless steel, provide some thread lubrication, have locking properties, have a delayed setting time, and fill the gaps between the threads enough to prevent corrosion.  This is what I bought yesterday and used on a bolt in a stripping test today.  So far, the stuff does all five of the ideal things.

https://tdsna.henkel.com/americas/na/adhesives/hnauttds.nsf/web/DF25E134F03D909B882571870000D81B/$File/567-EN.pdf

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3563 on: March 10, 2020, 01:45:41 PM »
The 567 threadlock was applied last night to the bolt flange and threads.  The bolt was installed and tightened down.  It was removed this morning and more effort was needed to do this than to install it.  The 567 locks the threads sorta not a much as blue threadlocker but more than none at all.  That is what I want.

The threads were wiped clean, more 567 was spread on the threads and flange, and a stripping test was done.  The test was stopped before anything yielded.  The potential clamping force this bolt can provide is far more than what I need.

The insert provides more external thread area in the aluminum wheel to resist shear as well as a longer engagement length.  Maximum preload force for internal thread shear was 2,240 pounds using the 0.64 safety factor.  Now it is 5,240 pounds in the wheel using the same factor.

Internal shear in the insert along the titanium bolt is increased, too.  This is 'cause the yield strength of the steel insert is much more than the aluminum.  Max preload was 2,240 pounds and it is now 4,610 pounds.

A persuasive argument is made for using a 0.5 multiplier, instead of 0.64, in the article with the Hooke's Law formula previously posted.  The maximum recommended preload for the bolt in tensile load changes to (0.5 / 0.64) x 4,640 = 3,620 pounds using this formula.  That is the force that will be used for this bolt.  Stretch is 3.62 x 0.000835 = 0.0030 inches at this load.  That is well within the capacity of this connection and it equals between 15 and 16 lbs-ft torque.   

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3564 on: March 10, 2020, 11:45:34 PM »
The little pup is growing very fast.  She is noticeably bigger week by week.

This is the Bonneville hub.  Note the amount of metal surrounding the wheel bearing.  It is well supported.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3565 on: March 10, 2020, 11:50:10 PM »
This is the Tiger hub.  Note the lack of metal and support around the bearing.

The skinny bearing is for a Tiger.  A wider double row one will be installed.  This will reduce the stress on the bearing housing to just over half of what it was with the Tiger bearing. 

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3566 on: March 17, 2020, 11:11:03 PM »
This is the brake side of the rear wheel with threaded steel inserts in the bolt holes.  The inside face of the spacer that holds the brake disk is shown.  The brake side wheel shroud fits onto the inside face of this spacer.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3567 on: March 17, 2020, 11:15:30 PM »
This is the outer face of the spacer showing the brake disk attached.  The next picture shows the spacer and disk on the wheel with the titanium bolts.  These are the bolts that gave me so much work trying to solve the thread stripping problem.  That is cured now.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3568 on: March 17, 2020, 11:22:38 PM »
This is the outside face of the brake side wheel shroud.  The parts were coated with ACF 50 anticorrosion spray before being riveted together.  This prevents corrosion between the pieces.  The next picture shows the inside face of the shroud.  It is reinforced around both edges.  A 1/4 inch thick spacer is riveted to the outside face of wheel shroud.

Offline wobblywalrus

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Re: Team Go Dog, Go! Modified Partial Streamliners
« Reply #3569 on: March 17, 2020, 11:27:38 PM »
This is the retaining ring that will be attached to the inside face of the shroud.  This is the ring bolted in place to hold the shroud to the brake disk spacer.  The retaining ring and shroud can be removed in instances when I do not want to use a covered rear wheel.