NASA fastener design manual

NASA Reference Publication 1228, from March 1990: Fastener Design Manual. By Richard T. Barrett, Senior Aerospace Engineer of NASA Lewis Research Center.

NASA Fastener Design Manual

This is a not-too-technical useful guide, loaded with plenty of debunking of fastener myths, and complete with numerous helpful charts and tables about fastener styles, torquing, identification, plating, lubrication, etc. Covers nearly all types of fasteners and fastener-related products, including many common commercially available parts and materials. Comes with three useful appendices: Bolthead Marking and Design Data, Bolt Ultimate Shear and Tensile Strengths, and Blind Rivet Requirements.

Looks like Barrett is/was (probably retired now) "The Fastener Guy" at NASA. In addition to the manual above, he has a lengthy 9-part fastener design course on YouTube (part 1 below):

https://www.youtube.com/watch?v=D6zaVhQkwnY

Barrett also published his Fastener Design Course in PDF. Barrett's fastener educational efforts were so comprehensive that he was awarded the Federal Laboratory Consortium Award of Excellence in Technology Transfer for 1993.

Some screenshots from the PDF link above:

https://diqn32j8nouaz.cloudfront.net...er_design1.jpg

https://diqn32j8nouaz.cloudfront.net...er_design2.jpg

https://diqn32j8nouaz.cloudfront.net...er_design3.jpg

https://diqn32j8nouaz.cloudfront.net...er_design4.jpg

And here's the PDF again:

NASA Fastener Design Manual


Previously:
https://www.homemadetools.net/forum/...pacewalk-51059
https://www.homemadetools.net/forum/...on-tools-58884
https://www.homemadetools.net/forum/...-orbiter-61787

Thanks Jon,
This is a subject that concerns us all and I for one always have something new to learn. It is also one of the biggest problems I come across. My all time favorite being 3/8" bolts in M10 holes and always in the most inconvenient and hard to access place. Second is wrong tensile rating and not torquing to correct tension or stretch followed by incorrect and/or mismatched bolt heads/ nuts. Dodgy anti-vibration control is up there too.

Spent some time as a Mechanical Inspector for a considerable manufacturing corporation. Grade marks and countries of manufacture for fasteners was a regular assignment too. Rc hardness, plating, size and pitch, headstamps, design related dimensions like you see in the Machinery Handbook, are just a few.
Counterfeiting of hardware is widespread; hence screening EVERY package, regardless of distributor, even those purchased for maintenance department. Now, to some it would seem obvious that substandard hardware is unacceptable in items built for the government. But maintenance? Sure.
You want SAE Grade 5's holding up that overhead conveyor or just some interpretation of same? Crosby or equivalent lifting eyes or something marked 'China'?

Taking a deep dive into fasteners might be one of the next chapters for online DIY communities. There are various anecdotal examples of well-placed people insisting that problems with vehicles, machines, and parts are frequently traced to fastener failure. But these statements don't correlate with significant fastener knowledge among hobbyists. We've all seen countless DIY builds of all kinds on the net. Very few of them pay much attention to fastener selection.

Very true. Torquing to correct tension is often overlooked as well, I spent a lot of time at one job repairing the stuff-ups of a bloke we called 'Stupid Man',(he was a body builder and wanted everybody to use 'Super Man' as his nick-name),who once told me he liked to do bolts up tight and then "give them a tweak until I feel them give".
Jaws dropped at this statement and it explained why I spent so much time on my shift re-doing everything he touched.
I've also seen people torque down a fastener and just leave it instead of backing it off and re-torquing. A recent article in Engineering 360 on this subject stated that initial give occurs in 50 - 100 milliseconds so it is no trouble to do the job correctly.
I also used to win 'smoko' bets by getting fellow workers to torque by hand bolts in a torque tester with the readout covered. It was amazing how far out most were on small fasteners but good to see how close a few well experienced hands were. I had the advantage of practice using a scale.

This part about how helical spring lock washers are useless for locking is interesting:

https://diqn32j8nouaz.cloudfront.net...sher_quote.jpg

I see in the N.A.S.A. Fastener Handbook that as with life the universe and everything the answer is 42. That is an astounding 42% of joint failure is due to installer error! 14% wrong preload and 28% improper assembly.
A common cause of both that I have seen regularly is dirt. I see people pull things apart without cleaning the area first and then give a cursory wipe with a dirty rag before assembly, or more correctly this is what I find has happened when doing repairs. A collection of old blunt taps are ideal for cleaning tapped holes and the smaller sizes can be run in and out very quickly with a reversible air driver,(drill), an air nozzle with an extended reach can be made to blow out debris. Studs can have a die nut run down them or wire brushed and a few minutes at a wire brush on a bench grinder will clean up various bolts, in the field shaking fasteners around in a bucket with solvent will usually suffice.
The worst thing about diagnosing a failure caused by lazyness or stupidity is that you usually know the problem was caused by someone who should have known better.

Interesting topic No time for an in depth response just now. My through the life experiences have enabled me to witness just about every type or cause of failures imaginable many caused my me while going through the learning curve starting at a very young age. but by far the most interesting ones were the ones others caused from shear lack of attention to the task at hand IE using the wrong fastener for the task over / under torquing, using too short of a bolt in blind hole assembly stripping out the hole or bolt then trying to compensate by replacing with a too long bolt and washering up to compensate for over length when the proper way to do the repair would have been to make a thread repair in the hole by either drilling out threading and installing a thread repair incert or drilling out threading and installing an oversized fastener if possible or a stepped down stud so the assembly would be held with a nut, or extreme cases having to drill out the hole to a taper then filling the hole with weld re drilling and taping the hole back to original
I learned early on to never allow a helper to use my extended length combination wrenches during re assembly of anything always give them a shorter version and a torque wrench preferably one that is adjustable with a torque limiting clutch not one that simply clicks at the preset torque other wise they inevitably would over torque

Quote:

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Originally Posted by Jon

This part about how helical spring lock washers are useless for locking is interesting:

https://diqn32j8nouaz.cloudfront.net...sher_quote.jpg

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It is also baloney. Split lock washers, at least good quality ones will highly resist the unscrewing of a bolt or nut. I've seen this first hand may times trying to take apart devices assembled with such lock washers. They will very much dig into the underside of the bolt head and very much resist your efforts to disassemble the joint.

Now maybe he has a different definition of what it means to lock the joint. If so it would be wise if the manual was updated with full qualification.

Quote:

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Originally Posted by wizard69

It is also baloney. Split lock washers, at least good quality ones will highly resist the unscrewing of a bolt or nut. I've seen this first hand may times trying to take apart devices assembled with such lock washers. They will very much dig into the underside of the bolt head and very much resist your efforts to disassemble the joint.

Now maybe he has a different definition of what it means to lock the joint. If so it would be wise if the manual was updated with full qualification.

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Yup, he can also be variously defining the phrases "normally flat" and "fully torqued", and he's careful to qualify his statement with "At this time". Also, if the fastener comes slightly loose, the lock washer is no longer equivalent to a solid flat washer; it can then maintain friction.

It's helpful to distinguish between "locking" and "retention" when discussing fasteners; these terms tend to be used interchangeably when in fact, they're entirely separate functions.

When speaking of a "locking" feature, this is a mechanism intended to prevent a fastener from loosening or otherwise disrupting the installed preload (otherwise known as "torque"). A "retention"" feature does not prevent a fastener from loosening. Its purpose is to retain or capture the fastener (once loose) from separating from its mating part and causing further damage. Cotter pins, safety wire, [lock washers] and related mechanisms will NOT prevent a fastener from loosening.

As noted, a good quality lock washer will, once relaxed (fastener broken free from its installed preload), resist further loosening of the fastener (acting as a retention mechanism). Fully compressed with the correct fastener preload, though, it acts as a simple flat washer with no locking attributes.

This video shows the differences.

https://www.youtube.com/watch?v=_ne19-3vkJg

Attachment 19037

Which also seems to be referenced in this article.

https://engineerdog.com/2015/01/11/1...out-fasteners/

So looking at the graph they are better than a plain washer but not much. I've mostly seen them used when the clamped material is softer hence you'd not want to tighten the bolt too much and also they would work better in that case.

Agreed Jon, the moment the nut is loosened, the raised ends of the washer dig in and resist further rotation. Quality in manufacture make some split washers more effective than others. One thing to note is that split washers are not generally used in the aviation industry. Here reliance is made on lock nuts of various designs, usually clamping the threads of the bolt through deformation of the nut or a nylon type insert. Inserts of this type are sometimes inserted into screw threads as well. The best know, and most disliked by aircraft mechanics, is the locking wire system where nuts and or bolts are secures in a tightening direction by stainless steel wire. Moving off the point, there is a right and a wrong way to fit a plain washer. Washers are stamped out and have a 'flat' side and a 'rounded' side. The rounded side should normally be under the nut and the flat side, which might have a bit of a feather on the edges, should be sited towards the casing secured.

That video and the related ones are truly excellent, a picture is worth..... Lets not forget simple staking as well, at least if done well fastener is reusable.
On the subject of insert type nuts there are 'Hex - Seal' brand nuts that while they have some anti-vibration traits their primary function is to seal against the ingress on contamination or fluid along the fastener.
This is a fascinating subject.
Best anti-seize next?

Nuts with inserts are manufactured by Simmonds Nuts, earlier versions had a fibre insert as a locking device. Later versions employed nylon and were known as Nylock nuts.

https://www.google.com/url?sa=t&sour...UzNNMybMPPhK-Q

I googled "what is the intended purpose of a split washer" and this was among the first links returned. As mentioned previously, the term "lock" is apparently open to interpretation, especially by those folks at NASA. It seems these weren't meant to "lock" something, and are incorrectly named in the public eye of most hardware stores.

Over-torquing has well known results, crushing, stripped threads and broken studs/bolts being the most obvious.

What is less understood is the results of under torquing.

In a Douglas Aircraft publication I had eons ago there was a large section on torquing and correct torque procedures with lots of emphasis on determining the running torque on a friction lock-nut (nyloc or metalok) and adding that to the required torque to determine the correct torque setting for the wrench. Using only the lubricant specified (Xxxx or none), surface cleanliness and other factors were also discussed

Most important to me was the long paragraph discussed actual tests to determine the results of under-torquing and discussed why an under-torqued joint could fail (bolt shear or component material failure) in as little as 4,000 stress cycles whereas the identical test piece correctly torqued lasted close to 200,000 cycles before failure.

Here's an ad for the 'Hex-seal seel nuts'. I worked a while in the waste industry and the leachate that developed in the back of packers did not always fall out with the rubbish. Corrosive and very bad if it was in a pocket when welding a tear in a bin. This stuff was a great penetrant and would migrate huge distances and there was always the lazy guy who could not be bothered to put any sort of sealant or lube on fasteners. Apart from correct torquing procedure I am of the opinion that prevention of a problem is far easier than dealing with a problem,(Murphy's Law applies to weather, location, time etc),and hidden corrosion is a problem.
I was told the first day of my apprenticeship:
" Do the very best job you can and think of the next guy because that 'next guy' might just be you". I have never forgotten that and just wish it had been drummed into a few I have met early on.

Attachment 19098

I forgot to add this.:embarrassed:

I had to go and look at some torque charts which was interesting. I'm in the habit of always lubricating threads with something except when there is a specific callout not to, plated threads are an example as the plating can be the lubricant. Zinc and Cadmium 1 are the most common. These platings are usually associated with lower grade tensile fasteners but have some valuable attributes such as not being great contributors to Hydrogen embrittlement, both are good lubricants under pressure and both provide cathodic protection. The tribological interactions as a fastener is tightened and the effect of surface treatments is something that any Aeronautical Engineers on this site would I hope be able to explain in a bit more depth than I have knowledge of.
Attached a couple of charts.Attachment 19111Attachment 19112Attachment 19113

My pet hates are: lock washers under nyloc nuts, using two nyloc nuts to lock a nut in place and making slim nuts by cutting one in half. This stupidity also extends to the use of pet tape (plumbers tape) on hydraulic and compression fittings. Pet tape is only for use on tapered fittings like BSP. stopping a leaking compression fitting on a water pipe might work in the short term - but you know its wrong. there is no way on earth you would perform such stupidity if it had 10K psi behind it, so why do it even though you know its wrong. Building machines and equipment using mixed fasteners IE metric and Imperial, not trying to standardise when using Allen studs. Perry Tritech in Florida was fantastic for this not to mention the mix of hydraulic fittings. To be fair the most fantastic thing they did do was use JIC fittings, brilliant - love them. I had a discussion with a friend of mine recently regarding tolerances, Now Norman is a bit of a boffin and i'm a good old clanky. after several beers i was still trying to convince him that tolerances were just a way of designers covering their arses for misalignment of fixtures, i was irritating to the max. As one of our colleagues above has stated the use of 3/8 in a 10 mm hole - this may actually be within spec. i grew up on a farm and i'm sure we did far worse before i was brain washed by the establishment. 6 mm spout bolts (coach bolts if you are posh) were used every where, they have the tensile strength of custard, however i can always remember using old bolts as drawbar pins for towing four tonne trailers. i'm sure NASA would go to the far end of a fart to explain that we should use material of a certain diameter and tensile strength, purph - worked didn't it. I have never seen any calculations for the bolted gussets on any of Brunell's bridges. To be fair I have seen several 25 tonne shackles destroyed. If you intentionally abuse the the kit, it will fail, but ts sneaky it waits until you least expect it.
Only clowns set themselves up for deliberate falls.

Whilst on the subject of lock washers, who reuses them, What really. It is my experience that fasteners in aircraft are replaced with new whenever a part is removed. I remember watching an air accident investigation in which a cockpit window was replaced in a Boeing 737 - an incident occurred later in the aircraft's service which resulted in the window blowing out and the co-pilot hanging on the the frame of the window on the verge of being swept from the aircraft. the investigation found that the wrong fixings had been used when reinstalling the window. The engineer had gone to the stores and acquired the correct parts as detailed in the manual, gone back to the job, compared the bolts against those he took out. The bolts were slightly longer, he asked his supervisor for clarity and it was decided that the new bolts were correct and they would use them. They were not. The error had been made in stores where the bolts had been located in the wrong bin against the wrong part number. the location of the bin and the part number were correct. The question is how far can you go to question a suspicious part, if the part came from a trusted ISO supplier with a long history of successfully supplying parts would you not take it on trust, are you going to destroy a sample just to prove its reliability. A change could have been made to the part but the information may not have filtered through to all concerned, who's to say the correct bolts were installed in the window in the first place. The aircraft did successfully land without loss of life and the co-pilot it alive to tell his story of his birds eye view of outside the aircraft.

Fasteners is the most boring topic but like this discussion has proved its actually one of the most important and interesting topics.

Nylocs and metalocs on aircraft are re-used if they still have the required amount of running torque (and now days they are good for many re-uses).

The video you are referring to is actually about a BAC-111 and it was the Captain sucked out. Don't feel bad about getting it wrong, I teach this stuff and do not have perfect memory for it.

The video I use is similar to the one below followed by a ppt presentation of the root causes from the official investigation.

My instruction to staff is to use the appropriate bolt gauge before they leave store. A six to ten dollar tool (depending on the bolt type) that can save the stress of an inquiry, millions of dollars, and save having to find a supervisor.

Complacency is the number one cause of accidents, and not just in aviation

https://www.youtube.com/watch?v=pOcm6E10anI

Attachment 19528

I kept hoping by some miracle the captain would survive, but fully expected he was gone. I'm blown away that he survived that, and is still flying! Awesome!! I had not heard about this incident. Thanks for sharing this incredible story. :)

Thanks MiTasol
I will correct my memory banks, there is nothing worse than inaccurate information you can see what happens.
you are in a career working in an area I would have loved to be involved in - sounds sick to want to be an accident investigator but its with the best intentions. I'm quite a spiritual and sympathetic person and would be working to respect those lost and their families. Its interesting how many large corporations play the blame game, they always sound like they want the whole thing cleared up as soon as possible and argue the amounts of compensation. Believe it or not I would keep an open mind but see too many programs on air accidents where the assumption is pilot error. Its a miracle that people fly at all, if i told you to strap 150 tonnes of metal on your back and jump off a building I think I could work out the answer. in a large number of reports I have seen or read the pilot error accusation has been unfounded, ice actually played a big part in three, Pitot tubes, ice in fuel and the Airbus computer taking over the throttles and thinking it knew best resulting in a heavy aircraft running out of runway at takeoff.
God help us when they make us all have Autonomous cars. They are conducting trials in the UK with articulated trucks, 3 in convoy to be exact. Can you imagine the chaos that will cause when someone wants to pull on to the motorway from the slip road or they get there timing wrong for pulling off at a junction and have to try and get back into lane between the trucks.
All in the interest in road safety.

Well my chosen path wasn't to be, didn't do a degree and there is only two or three universities that cover aviation, I was in the Navy but unfortunately no aircraft in the engine room. Now too old, still looking forward to being a fireman or an astronaut though, if only as a child I wanted to be a farmer I would be living it up on a 145 acre farm now. If i prised it out of my brothers hands. Just a lowly engineer (engineering technician to be politically correct).

That was an amazing video, excellent graphics with some real shots. An amazing survival story.
On fasteners this is not NASA approved but does have a lot of useful information. It's from a local shop called The Bolt Shop who deal in fasteners and retainers of many kinds. I hope it is of use to someone as a handy reference.Attachment 19530

Forgot to say there is a rerun of a TV program called Mayday on one channel here and I'm very impressed with the detail into what caused an air accident. Even malfunctions are examined closely. What disturbs me is the amount of reported problems from pilots and maintenance crew that are just filed and not followed up until a disaster occurs.
With the aircraft windscreen the fact that somebody actually doing the job questioned the bolt supplied should have set off alarm bells somewhere, that pictorial of an accident trajectory I have copied and are going to print and glue to a wall as a reminder of how easy complacency can kill.

NortonDommi
Really good info thanks, i have downloaded it to my pdf library.

I guess for us home-brew / DIY enthusiasts is to know when to apply the appropriate standards, in a perfect world we should be professional in our hobbies and committed to maintaining a high standard of work. I'm guilty of building stuff without being particular about the overall build, however i do set certain rules of thumb which on the whole are overkill for hobby builds - or are they. keeping in the spirit of this post and as mentioned before should we as tool builders adopt the same standard we will be using at work or in our previous job roles, I say yes why not.
i am currently making a steel structure for a guy to support a balcony banister, it involves hiding a steel support inside his oak banister to prevent any possible event of a fall from the balcony should the wood rot and end up not fulfilling its task. My part of the project requires four wall fixings, two for the banister and two for the kicker bar, the front of the balcony has two upright steel box sections (which i did not make) The balcony itself is Ibeam cantilevered into the wall - solid as (again i did not make). The banister steel is my baby. So i have to consider the type of wall fixings, the load and stresses likely to be on them, the suitability of the wall for the required fixings. Then comes the angle plates i'm bolting to the wall, how thick should the steel be how to attach the steel inner support and wooden banister to the angle plates. So i'm using 8 mm plate the width and height of the banister, the plate has an angle welded under it to support the banister and used to bolt through fixing the banister to the wall. a steel frame extends out to the two front uprights and across the front of the balcony. This will be welded to the two uprights at the front of the balcony.
So applying some standards, welding should be by coded welder designed in such a way as to comply with numerous regulations and fit for purpose capable of meeting load requirements. I'm using 8 mm Rawl-bolts for the wall fixings which will have a predefined tensile strength, In the civil engineering world i would probably have to pay attention to the balcony itself even though its not part of my remit, if the balcony were to collapse the chances are the banister would go with it.
would the failure of the banister still be my fault, well technically yes. If it were solid and still hanging in the air then one could argue the banister performed its task.
we all make decisions like this every day especially with our homebrew projects. Actually taking the time to analyse a project and implement our knowledge of standards , health and safety etc then our hobbies need not be inferior to that we would do at work. Cost is always a major player in projects but it should not compromise our integrity. incidentally the experts can get it wrong on a biblical scale, they more than likely have cut corners to get there. I'm thinking of Grenfell tower in London UK, in this case standards were followed. https://www.youtube.com/watch?v=S4Ic7c5Qbdo.

An inferior cladding was used on the building which aided the fires spread up the building, it did meet the current building standards. The cause of the fire is thought to be faulty household appliance. At present there are hundreds of product recalls for faulty electrical goods, how many of these goods could have been in this tower? 100+?. Are the big electrical goods companies doing sufficient to recall faulty goods, we will have to wait for the incident reports findings to be published.

If you believe you are invincible and you are the safest in the world, it will bite you in the arse. The Titanic is just one example of this type of complacency. Humans are not invincible but unfortunately trying to convince your elders/superiors they are heading for a fall takes some guts and more than likely they wont listen. Attempts have been made to have an open door policy within companies but it tended to depend on who you are, the scroat on the workshop floor could be coming to you every day with crappy ideas, he only needs one good idea to save your company or save you money. It is for those in charge to learn how to manage people, having the right environment will go some way in trying to prevent mistakes like the bolts on the aircraft cockpit window.
If we are working on projects then the ones is on us to ensure some thought goes into what we expect the desired outcome to be.
so 55 mm bolts and 1" steel plate for my banister it is.

A company I was with had bid on and was awarded the contract to provide an architectural steel awning over the side walk of a concrete building that was being built. 2 of my young engineers and our architect had poured over the plans for a couple of weeks and could find no major dependencies in the proposed plans so it was submitted and approved by the consulting firm while I was away on business. When I returned I glanced at the layout only briefly then took a good look at what our architect had designed the weight was within parameters all fastenings and diagonal down bracing appeared to be fine, at first I was ready to stamp it for production but for some reason I decided to visit the site first just to double check the location where the awning was to be located. What I found was instead of a reinforced 300 mm thick concrete wall on the second floor as was specified in the original drawings the contractor had used solid concrete blocks with no vertical or lateral steel reinforcing and no continuous concrete beam had been poured at the level where the upper support plates were to be through bolted for the diagonal bracing.
I went to the general contractor to inquire about it and to explain that in order for my company to be able to provide the awning we needed at the very least a 600 mm reinforced beam poured a the specified location where our support mountings were to be placed.
He took exception to my conversation and asked me to leave stating that he had been building high rise buildings in the Middle East for 20 years and had never had one fail. So I told him and you can build this one with my blessings only it will not have our awning hanging over the sidewalk.
I then flew to Holland to visit with the Consulting firm and meet with the owner to formally void our contract based on public safety concerns. Armed with a copy of the original plans our drawings 3 structural analysis studies done by some of our younger engineers my personal study including wind loading, and a camera full of on site photos. 3 days later the general contractor was fired an new general hired and 10 sections of the 2nd floor wall was being torn down.

Hello MeJasonT,
Glad that can be of use. We had a lot of building rules changed here after the Christchurch earthquakes particularly after a building fell down killing a number of people. The inquiry found that the chief architect had no formal qualifications and had relied on B.S. and 'mates' to cover his butt for decades. No formal qualifications wouldn't matter if he had done the job to an acceptable standard but what made it worse was that he had altered the original plans to remove structural bracing and reinforcement at a critical junction. This had been picked up by some junior staff who were subsequently fired for raising questions about his competency.
Senior Council bureaucrats who had signed off ran and ducked and after 5 years no one was held responsible, the entire building industry has had an overhaul though with new "accountability measures" put in place whatever that means.
For the D.I.Y. guys this has ups and downs, one positive is if you want to build a balcony there are material specifications including hardware that must be used which has meant that the price of SS fasteners has plummeted due to increased supply and strength and safety are now BBQ conversations for more than tradies.
Frank, building fall down or burn down in the Middle East don't they? At least in China they shoot those responsible so they can't take shortcuts again.

In Sept of 2008 there was a little 6.1 near Qeshm Island in Iran I was up on the 32nd floor of a building being built in Kuwait City at the time it happened with no walls on the building yet only the concrete structure and the core and some of the floors had been poured we felt the building sway quite a bit even being several hundred Kilometers away. Towers down in Dubai were evacuated as a precaution that stupidly tall thing they have in Dubai now is supposedly rated to withstand a 9.1 but you wouldn't catch me in it I was invited to a conference to be held on the 65 th floor but as luck would have it I was in Germany at a trade show during the time it was to be held

I have to think there's something not obvious going on here. I've seen a lot of vibrating machinery in my time, and if most nuts loosened as apparently easily as it appears in the video, stuff would be falling apart all around us ...

IN the the video I suspect these fasteners were attached to a single member and the harmonic resonance was perfectly tuned for testing and demonstration purposes . in real world application while the possibility of perfectly tuned resonance does happen between dissimilar size and shaped parts it is rare that there would be only 1 fastener in place on critical structures or assemblies. blind doweling 2 parts together helps to elevate this possibility as well. but vibration is no where near the only cause of fastener fails, thermal expansion and contraction wind loading torsional stress tension loading and relaxing structural flex improper chamfering of the mating holes just to name a few

Fastenal Technical Reference Guide

https://diqn32j8nouaz.cloudfront.net...uide_cover.jpg

single member and the harmonic resonance was perfectly tuned, weh-hey sounds just like us guys her on the grandiose homemade tool forumartos. we should all get a pin.