Tom Morris Takeapart Hardware

[frank williams]

Does anyone have a set of Tom Morris takeapart hardware that they would like to part with.  OR ... a description of the arrow shaft parts that are used to make the connective pieces.  I go to the archery sites and I can't find any parts that look right.  Were the TM parts special machined parts?

[Dave_Trible]

Frank send me your address......I have some.

Dave

[Paul Walker]

Frank,
Be VERY careful of those if they are preassembled by Tom.
 His glue joints were not done properly, and I had one fail.
PM me if you need more info.

[Dave_Trible]

Frank in case you didn't see my PM.  I'm sending two sets.  When I heard about the issue Paul had I pinned these.   Also you will need to order some more 5-40 x 5/8 socket heads screws.....can't find the bag I had.

Dave

[Dick Pacini]

Does anyone have a set of Tom Morris takeapart hardware that they would like to part with.  OR ... a description of the arrow shaft parts that are used to make the connective pieces.  I go to the archery sites and I can't find any parts that look right.  Were the TM parts special machined parts?

The ones I made I used carbon fiber tubes because I couldn't find suitable arrow shafts.

[Dave_Trible]

The ones Tom made are titanium.  I don't know if they started life as an arrow or not.  They are harder than snot!  To me the hardest part with them is to get them mounted securely enough to the wood.  That is where I lost one at the Team Trials.


Dave

[Howard Rush]

They are harder than snot!

Snot is a sol or something.  I think Dave must have meant that they are harder than boogers.  Hope this helps.

[Dave_Trible]

Snot is a sol or something.  I think Dave must have meant that they are harder than boogers.  Hope this helps.

Thanks for claritin that up Howard.

Dave

[Steve Berry]

Thanks for claritin that up Howard.

Dave

Nasal issues are nothing to sneeze at....

Steve

[Paul Walker]

The ones Tom made are titanium.  I don't know if they started life as an arrow or not.  They are harder than snot!  To me the hardest part with them is to get them mounted securely enough to the wood.  That is where I lost one at the Team Trials.


Dave

That is interesting. Of all the ones I got from him, they were all aluminum.

Hmmmm.

[Dave_Trible]

These are nearly paper thin but can’t be squeezed or bent with your fingers.  I broke off drill bits drilling to pin them. 

[Paul Walker]

These are nearly paper thin but can’t be squeezed or bent with your fingers.  I broke off drill bits drilling to pin them.

How much did an assembled set of three weigh?

[frank williams]

I have a set of those .... the pink ones
I got them from one of the Russian / Canadians at the Nats one year.
The machining is beautiful .... immaculate ..... paper thin walls .... although dimensioned for a 3.5 inch wide fuselage ... I'll go weigh them

[Dave_Trible]

Frank these are yours when I can get to the post office.  They are spaced for 2 3/4” fuse I believe.  Paul I’m not home to weigh them.  They should be just a few grams less than what Frank has.

Dave

[frank williams]

I weighed the ones I have, they were from Konstantine.  The weight is 1.79 oz.
Once again, immaculate machining.

[Lauri Malila]

So, how do they fail? Have you had the Al component itself failing or the connection to the rest of the structure? L

[Dave_Trible]

So, how do they fail? Have you had the Al component itself failing or the connection to the rest of the structure? L

Lauri my only problem with them was getting them mounted to the wood well enough not to tear loose.  I think I had tried binding them to plywood with wraps of soft wire and epoxy.  That failed at our team trials at about 250 flights.  Those that had a structural failure occurred , I believe,  with the end fittings pulling out of the tubes.  These were put in with a glue of some type.  I drilled and pinned these fittings as a mechanical lock in.

Dave

[frank williams]

After a closer look at Dave's picture, I see that those are the Tom Morris ones.  What I was talking about had square cross beams for the spars and were machined aluminum.  Sorry for the confusion.

[Lauri Malila]

Just a small question related to the same subject;
I'm making the take-apart bits for my new model. I'll be a similar principle that above, with 3XM3 bolts in tension/wing.
The parts in fuselage are turned from 7075-T6, and the parts that hopefully stay inside the wings are milled from 7075-T651.
The T651 sheet is rolled, and it is generally recommended to align the stresses with the rolling direction. Is the rolling direction same as the surface texture in the raw sheet? L

[Paul Walker]

Just a small question related to the same subject;
I'm making the take-apart bits for my new model. I'll be a similar principle that above, with 3XM3 bolts in tension/wing.
The parts in fuselage are turned from 7075-T6, and the parts that hopefully stay inside the wings are milled from 7075-T651.
The T651 sheet is rolled, and it is generally recommended to align the stresses with the rolling direction. Is the rolling direction same as the surface texture in the raw sheet? L

I use 7075-T7351 to avoid the stress corrosion issues in the T6xxx tempers.  The T6 tempers in 7075 if left with a residual stress across the ST direction can and will crack. I have been witness to several 7075-T6 parts cracked in half before even being installed on aircraft.

If using the bolts in tension, the threads can have a residual stress in the ST direction in the fuse side.

The slight drop in strength of the T-75xx tempers is not worth the risk on my models. Min machine gage generally sets the thickness in the cross fuse part.


If I hadn't seen this in real life, I likely would not have bothered.  But, it does happen.

[Lauri Malila]

Thank you, Paul.
It’s just that my material source has in general the round barstock in T6 and sheet material in T651.
The T6 has more internal stresses, but as those parts are made with lathe, deformation should not be a problem, while a T6 sheet material can and will deform if skimmed asymmetrically from raw material. For this reason the sheet is usually stretched/T651 to eliminate internal stress.
But back to the original question; is there a notable difference in tensile/fatique strenght in rolling direction vs. 90° to it?
Remember that my parts are tiny, they won’t crack due to internal stresses. L

[Paul Walker]

Thank you, Paul.
It’s just that my material source has in general the round barstock in T6 and sheet material in T651.
The T6 has more internal stresses, but as those parts are made with lathe, deformation should not be a problem, while a T6 sheet material can and will deform if skimmed asymmetrically from raw material. For this reason the sheet is usually stretched/T651 to eliminate internal stress.
But back to the original question; is there a notable difference in tensile/fatique strenght in rolling direction vs. 90° to it?
Remember that my parts are tiny, they won’t crack due to internal stresses. L

Small parts have residual stresses no different than large ones. In this case, torquing the bolts down puts stresses in the cut threads of the part in the wing. Your choice.

No, there is not a significant difference between L and LT directions in 7075 plate. Have at it!
P

[Brett Buck]

I am curious, what sort of margins are you trying for on these parts?  I would have expected that any concern over stress corrosion/cracking would be obviated by having about 10x margin.

     Brett

[Paul Walker]

I am curious, what sort of margins are you trying for on these parts?  I would have expected that any concern over stress corrosion/cracking would be obviated by having about 10x margin.

     Brett

The ones I designed and had machined clearly don't have a 10x margin. I didn't want the extra weight.

[Lauri Malila]

Would you mind sharing your design, Paul? I have an idea in my head but haven’t drawn anything yet.

[Brett Buck]

The ones I designed and had machined clearly don't have a 10x margin. I didn't want the extra weight.

   You're obviously more knowledgable about it than I am.  I would sure be nervous counting on the rolling/machining stresses to be understood well enough to cut it that close in the places that matter. Particularly when it saves 1/2 ounce on a 60 ounce airplane.

    Other parts of the same assembly *are* probably way overbuilt (like the screws - bigger than necessary presumably to reduce the load on the threads).

   What sort of tension do you suppose is on that fitting?  Back of the envelope, I get about 200ish lbs.

       Brett

[Paul Walker]

   You're obviously more knowledgable about it than I am.  I would sure be nervous counting on the rolling/machining stresses to be understood well enough to cut it that close in the places that matter. Particularly when it saves 1/2 ounce on a 60 ounce airplane.

    Other parts of the same assembly *are* probably way overbuilt (like the screws - bigger than necessary presumably to reduce the load on the threads).

   What sort of tension do you suppose is on that fitting?  Back of the envelope, I get about 200ish lbs.

       Brett

I back calculated what a "normal" built up wing can withstand. I came up with about 400 pounds.

My area of concern is only in the threads. There you could get stresses in the ST direction, which has the low K1SCC value  in 7075-T6xxx tempers. 7075-T73xxx has none of those issues.

The T-6 temper works great as long as there are no constant strains in the ST direction.

As far as a factor of 10...7000 series Al have very consistent properties, so there is no significant risk using the Mil standard numbers. So, I  use a factor of safety of 2 on my back calculated number. It has not failed to date for those reasons.


Now there was the time that I nearly hit Howard with a wing departing  from the Mustang I used in Muncie in 2004. That was prior to those competitions, and was due to a single missed glue joint on a shear web near the wing splice
 Oops  my bad.  It withstood the very strong wing on one of my qualifying flights at the WC's in Muncie.

[Lauri Malila]

Sorry Paul, I don't quite understand the terms you use, so I'd need a practical example. From experience I know that a well made M3 thread in these materials is practically indestructible, especially if hard anodised and lubricated.
But I also know from practical experience that a 4-40 thread is slightly better than M3 in aluminium, even when you loose a little in screw cross area. Does the thread type make any difference how the aluminium around it is stressed?
I can still change to a Yatsenko-style unit but I feel that the tension bolt system could be lighter. I will try to make a drawing soon, it'll be easier to explain my ideas like that. L

[Paul Walker]

L,
your M3 will not make much difference. Go ahead.
I like this style better  and is what I use. I also don't use just any 4-40.  They are high strength, grade 8 here. I don't know the equivalent metric designation.  As long as they are clamped up tight, they will not see any cyclic load, and last a very long time.

Have at your design. Please show your pictures when done. I always like to see others designs.
P

[Brett Buck]

I back calculated what a "normal" built up wing can withstand. I came up with about 400 pounds.

    I did it from the other end, what sort of load you get in the hardest possible corner. I got about 60ish pounds at the speeds we fly. Making a guess about the lift distribution, I figured 30 lbs a side, centered about 12" away from the fuse. At the fuse, and a 2" spacing, gets a torque of about 180 lbs a side, top gets compression, bottom gets tension. I figure 180 lbs in tension is the part I would be scared about. So I would test a Tom Morris-stye hardware to about 180 in tension, give about 50% for acceptance testing, so maybe 240 lbs, and qualify to maybe 400 or to destruction.

    I also figured that the threads in the insert were a weak point from a materials/yield standpoint. I would think a thread insert would make it a lot tougher. But the glue joint  is the part I would put maximum margin on, and be the most worried about, because the prep, etching, and bonding is so prone to procedural problems.

   The screw should be plenty good, but failing a thread insert, I would want to make it bigger to reduce the load on the threads.

   Brett

[Paul Walker]

    I did it from the other end, what sort of load you get in the hardest possible corner. I got about 60ish pounds at the speeds we fly. Making a guess about the lift distribution, I figured 30 lbs a side, centered about 12" away from the fuse. At the fuse, and a 2" spacing, gets a torque of about 180 lbs a side, top gets compression, bottom gets tension. I figure 180 lbs in tension is the part I would be scared about. So I would test a Tom Morris-stye hardware to about 180 in tension, give about 50% for acceptance testing, so maybe 240 lbs, and qualify to maybe 400 or to destruction.

    I also figured that the threads in the insert were a weak point from a materials/yield standpoint. I would think a thread insert would make it a lot tougher. But the glue joint  is the part I would put maximum margin on, and be the most worried about, because the prep, etching, and bonding is so prone to procedural problems.

   The screw should be plenty good, but failing a thread insert, I would want to make it bigger to reduce the load on the threads.

   Brett

Brett
I have ZERO glue joints in my system. It is CNC machined, and the only glue is attaching it to the model. No issues.

[Paul Walker]

Lauri and Brett,
Attached is the design I have used for a number of years now.
P

[Paul Walker]

Laurie and Brett,

Attached is my current configuration. Hope it explains things.
P

[Brett Buck]

Brett
I have ZERO glue joints in my system. It is CNC machined, and the only glue is attaching it to the model. No issues.

  The Tom Morris type uses a insert glued into a tube, though, right?  I thought that's what we were talking about.

     If was going do to anything with the screws in tension, certainly, just take a single piece and machine a groove on the wing side to allow you to insert the screw. The one set I made was more-or-less like that, but had a heli-coil (actually, two heli-coils back to backbecause I figured taking it apart and putting it together would wear the (6061-T6) aluminum. But I also had 6-32 screws.


     Brett

[Brett Buck]

Laurie and Brett,

Attached is my current configuration. Hope it explains things.
P

 I get that one, you would not like mine! I will see if I can find it, but mine probably weighs about an ounce, ounce and a half more than that, and only has a few grooves cut in it with a 1/8 ball-end mill to remove material from the 3/8 square stock, and a bunch of holes drilled in the free ends for pins into the spar. Yours is the professional structural engineer version, mine is the "I can get my buddy to machine some grooves and I have a hacksaw" version.

     Brett

p.s. On further examination, I can see how to cut most of it, but how do you get the deep blind hole with a square cross-section - a shaper with an offset tool that looks like a boring bar? some sort of a broach?

[Lauri Malila]

…or EDM, that would be the easiest.
Thanks Paul, that really helps.
I had spmething similar in mind, except leaving the top (outer) side of the wing parts open, so they would have a U-form. That’s of course easier to make with normal machine tools.
What’s the 0,45” wide groove for, in the roots of the wing parts? Looks like something locks in there..? L

[Lauri Malila]

This looks a little scary. I’d continue the theead a little deeper into the square part.

[Paul Walker]

…or EDM, that would be the easiest.
Thanks Paul, that really helps.
I had spmething similar in mind, except leaving the top (outer) side of the wing parts open, so they would have a U-form. That’s of course easier to make with normal machine tools.
What’s the 0,45” wide groove for, in the roots of the wing parts? Looks like something locks in there..? L

Nothing but weight removal.  I glue in a piece of balsa to fill it for the joint in the wing.

[Paul Walker]

This looks a little scary. I’d continue the theead a little deeper into the square part.

Hasn't proven to be an issue with quality materials on numerous planes for the last four years.

Can't cut much deeper as the tapered wedge is close. I didn't want a breakout there.

[Paul Walker]

     Brett

p.s. On further examination, I can see how to cut most of it, but how do you get the deep blind hole with a square cross-section - a shaper with an offset tool that looks like a boring bar? some sort of a broach?
[/quote]

The hole isn't blind. The end is open to get the cutting tools in there.  This is done with CNC machining driven from a CAD drawing. No EDM here! There is a time and place for that, but not in a critical structural part.

[Paul Walker]

  The Tom Morris type uses a insert glued into a tube, though, right?  I thought that's what we were talking about.


     Brett

We were, but Frank mentioned that he was asking about the square machined ones, and off we went.

Tom's problem was his preassembled joints. He employed workers to make these, and they glued them. I do not know his process. I decided to test them when one of my preassembled joints let go.
I took a preassembled joint, cut the cross fuse tube off about a half inch from the joint. then I cut a spiral groove in the tube at the joint down into the male part. I did this also with my glued joint. O om's, I was able to simply peel the tube off of the joint. The glue simply didn't adhere well at all. on my joint, I had to grind the tube off as there was no way I could peel it off. Yes, I know this is not the exact way the glue is loaded, but is indicative of how well the glue is adhering to the parent parts.

I do not know how Tom prepared his joints, if at all.  I roughed up the surface on the tube ID, and the male part OD. They were then cleaned in 99% alcohol, and dried. JB Weld, steel type, was the glue that worked well. I mentioned this to Tom, and he immediately stopped doing pre glued joints.  Bottom line is that Tom's will work fine, as long as the glue joint is prepared properly. His materials have proven to be fine. However, I have never liked those glue joints in my planes, and once a quality machinist was found, the new design was used since then.

[Lauri Malila]

Hasn't proven to be an issue with quality materials on numerous planes for the last four years.

Can't cut much deeper as the tapered wedge is close. I didn't want a breakout there.

That's interesting, or actually eye-opening.
Simple cross-section calculations show that in clean tensile stress, it's the weakest link of the system. But still, with a yield strength of 410MPa, that section should tolerate about 570kg pull before plastic deformation.
as a comparison, the square tube section would need about 650kg, and the center H nearly 1050kg.
So, it's very easy to over engineer these things. With this small cross sections, the compression strength becomes a bigger challenge.
What kind of main spars do you use with his system? Sq. balsa with some carbon on it, I guess..?
Thanks a lot again, Paul. I'm off to drawing board!

[pmackenzie]

     Brett

p.s. On further examination, I can see how to cut most of it, but how do you get the deep blind hole with a square cross-section - a shaper with an offset tool that looks like a boring bar? some sort of a broach?


The hole isn't blind. The end is open to get the cutting tools in there.  This is done with CNC machining driven from a CAD drawing. No EDM here! There is a time and place for that, but not in a critical structural part.

The drawing shows square corners on the inside, are they actually radius-ed based on the diameter of the cutting tool used?
That tool diameter would also have to match the rads in the bottom of the pocket, unless they are machined as a surface.

To my eye, as drawn that feature would be easiest with an EDM sinker. Assuming you have an EDM available

FWIW, I have generally used "Yatsenko" style that put the bolts in shear.
Seems a lot easier to make (most parts can be done from G10 with hand tools), and easy to tie into the wing spars.

Pat MacKenzie

[Lauri Malila]

As Paul hinted, electoerosion is notbreally for critical structural parts; it can introduce micro cracks and too luch heat, especially in a such thin walled part. My guess is a rotary broach. But I’m not sure if such deep holes can be produced with that.

[Howard Rush]

Here are a couple of my joiners, made to Paul's specs (I think).  Both types have held up well in stunt service.  The round one in the picture looks bent, probably because the negative got distorted when I developed the film.  The second picture shows installation in the dog: two square ones in the front and a round one in the back. I didn't use my third square one in the airplane because the screw holes were indeed not deep enough. 

[Brett Buck]

The drawing shows square corners on the inside, are they actually radius-ed based on the diameter of the cutting tool used?
That tool diameter would also have to match the rads in the bottom of the pocket, unless they are machined as a surface.

   That was what throws me about it.  If you wanted a 1/32 radius, you need a 1/16" ball end mill about 3 inches long, if they even make such a thing. Even a 1/8" would be under extreme danger of at least deflection if not breaking. The equivalent part on mine was a "U" channel, and the crossbar was an "I-beam", in both cases, for machining access, and my limited machining skills. I looked around to take pictures but I can't find it.

     I found a different solution to take-apart airplanes - bought a mini-van and quit the FAI.

     Brett

[Howard Rush]

The drawing shows square corners on the inside, are they actually radius-ed based on the diameter of the cutting tool used?

Corners are square.  Parts are made in Canada, where they know how to do fancy stuff.

[Lauri Malila]

   That was what throws me about it.  If you wanted a 1/32 radius, you need a 1/16" ball end mill about 3 inches long, if they even make such a thing. Even a 1/8" would be under extreme danger of at least deflection if not breaking. The equivalent part on mine was a "U" channel, and the crossbar was an "I-beam", in both cases, for machining access, and my limited machining skills. I looked around to take pictures but I can't find it.

     I found a different solution to take-apart airplanes - bought a mini-van and quit the FAI.

     Brett

Everything is available, for example these cutters that would easily produce such deep square blind hole with a 0,75mm corner radius. Also available with a ball-end. I do it often with manual machines, too.  But honestly, as a mechanic, I don't understand the added complication of such a deep blind square hole. To me an U-beam is almost equally elegant. L

[Paul Walker]

Here are a couple of my joiners, made to Paul's specs (I think).  Both types have held up well in stunt service.  The round one in the picture looks bent, probably because the negative got distorted when I developed the film.  The second picture shows installation in the dog: two square ones in the front and a round one in the back. I didn't use my third square one in the airplane because the screw holes were indeed not deep enough.

Or, you screw was too long!

[Paul Walker]

Everything is available, for example these cutters that would easily produce such deep square blind hole with a 0,75mm corner radius. I do it often with manual machines, too.  But honestly, as a mechanic, I don't understand the added complication of such a deep blind square hole. To me an U-beam is almost equally elegant. L

The machinst had the tools to get it done, so it was done!

[Brett Buck]

Everything is available, for example these cutters that would easily produce such deep square blind hole with a 0,75mm corner radius. Also available with a ball-end. I do it often with manual machines, too.  But honestly, as a mechanic, I don't understand the added complication of such a deep blind square hole. To me an U-beam is almost equally elegant. L

    If you are digging 2" deep with that end mill, in carbide, I hope you are wearing eye protection and a flak jacket.

   Again, I intentionally limit myself to things I can do with a drill and some files in my bedroom, and taking it to my buddys garage for milling was way out of my comfort zone.

   I like Paul's co-axial alignment pin. Making a separate hole for it on mine was a pain to set up accurately enough.

     Brett

[Lauri Malila]

No. If you look at the drawing, the hole is 1,07” deep.
It’s not dangerous at all; you first drill a center hole and then proceed with the square X/Y movement, removing 0,5mm at each pass. DRO is your friend.
But it’s quite slow, of course. You'll need watchmakers patience. Biggest problem is evacuating the chips from the hole; working at home I cannot use high pressure coolant.
Anyway, I’ll make my parts
With a П-channel where the spar is glued. I guess the channel will be something like 40…45mm long. L

[Kim Doherty]

Lifted from an older post:

Some more "Grist for the mill"

Below I have attached some pictures of different take apart systems and construction details.


The first image shows the Russian take-aparts referenced by Frank (I think) that he received from Konstantine.  Note that the ends of these parts come round as they were made on a lathe. They need to be milled square prior to gluing. Very light and well made. Anodized Aluminum, 3mm bolt.

The next four images show the wing take apart pieces of the original SkyWriter. You will note that the bolt (sometime refered to as the "Jesus Bolt") is in shear. This is by far the prefered way to make a take apart but it also reqires some fairly exact milling. Most take apart fasteners will have the bolt in tension. ( I have never had one let go)

Note that the spar itself is made of maple. The aluminum pieces are epoxied and pinned with brass rod. The maple main spar has sweep built in and is also a machined piece. (Maple machines very well!) Notice the vertical end grain bracing between the spars. The spars must not be allowed to move towards each other or the wing will fail at once.


The last set of images shows the wing take aparts from "Shockwave". Milled "U" channel, square ends, turned mid sections for lightness, 7075 aluminum, 4/40 thread. Very light (total weight of all take aparts for complete model = 46 grams).

[Shorts,David]

 

     I found a different solution to take-apart airplanes - bought a mini-van and quit the FAI.

     Brett

I was explaining take apart construction to my dad without ever really doing it. We decided a van and an extra week driving was a better option. But I'm committed already so I'm trying it out.