Site Logo

 
It is currently Tue Jul 22, 2014 12:44 pm

All times are UTC - 6 hours




Post new topic Reply to topic  [ 30 posts ]  Go to page Previous  1, 2, 3  Next
Author Message
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Sun Mar 15, 2009 11:24 pm 
Offline
User avatar

Joined: Wed Jan 28, 2009 9:53 am
Posts: 928
Location: Eagan, MN
metis wrote:
all of those examples are inline with axis of layup and not dealing with crossing impacts. think of a fiber golf club: it transfers a lot of energy through some spring and momentum to another object via the head but it you hit it against a tree it shatters. we need to hit a tree.

You've used this example before, with me, and I don't see how it necessarily means fiberglass is a bad idea for our Spoon handle.

A golf club is all about impact. It just has a surface designed to withstand the impact--the angled face on the metal head, obviously. The shaft can flex and/or twist slightly at the moment of impact, then recover. It's not a problem because the head is much more dense than the shaft. By that time the ball has already been propelled downrange, but there still is bending and reformation.

Now, if you lose your temper and smack that damn oak tree that's always in the way with your 9-iron as hard as you can, and in your blind rage make contact with the handle, then yeah, your spendy carbon-fiber shaft will probably evaporate into flying threads (and woe betide the poor schlub standing in the path of the club head). But if you manage to hit the trunk dead-on with only the head, well, you'll put a nasty dent the bark. Feel better now, bruiser? :P

Anyway that's what I think you're picturing, since our "club" (the Spoon) isn't hitting the "tree" (horizontal 2-by-4 at the top of the frame) with the "head" (the bowl of the spoon). Bear in mind we've already got a few small mitigating factors to that impact--the frame is well padded at that point, and if the handle is positioned just right in the rope spring, the Spoon should hit the pad exactly at the bend, with the angle of the pad matching the angle of the bend, so that the heavy bowl of the spoon is supported & its tendency to flex downward is reduced. (The weird 90-degree spoon head is practically pointing in the direction it's being propelled already, in a ballistically inefficient and un-catapult-like manner, because it happens to be the way Spoonbridge and Cherry was sculpted.) So... all we should have to do is make sure the Spoon's handle is hardened at the point of impact.

A fiberglass boat has a sort of built-up "lip" around the gunwale, where it's likely to run into piers, the dock, other boats, etc. (Don't drink and sail, y'all.) It is possible to reinforce fiberglass against impact with more fiberglass. Of course, it's better if you use those rubber bumpers, 'cause that's what you bought them for, cap'n.

_________________
my workplace blog
my builder blog
my personal blog


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Sun Mar 15, 2009 11:33 pm 
Offline
User avatar

Joined: Wed Jan 28, 2009 9:53 am
Posts: 928
Location: Eagan, MN
OK, here's Tiger Woods in slow-mo, showing me that the shaft of his driver doesn't actually flex much at the moment of impact with the ball. The ball does all the flexing.

The shaft DOES flex as he initiates the swing, though, and when he reverses direction at the top of his swing to bring it down, and then again after he's hit the ball downrange & is slowing the club down (presumably so he doesn't strangle himself and/or twist around backward before flopping face-down onto the green).

Still: as long as the swing arm (club, spoon, hammer, drumstick, etc.) takes the impact at a point where the surface has been engineered to withstand it, the rest of the system will survive just fine.

_________________
my workplace blog
my builder blog
my personal blog


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Mon Mar 16, 2009 12:45 am 
Offline
User avatar

Joined: Wed Jan 28, 2009 9:53 am
Posts: 928
Location: Eagan, MN
Waaaaait a second. :lol:
metis wrote:
now, the trebu-foshay would be ideal to have a foam frame laid up around a...

_________________
my workplace blog
my builder blog
my personal blog


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Mon Mar 16, 2009 10:27 am 
Offline
User avatar

Joined: Wed Jan 14, 2009 10:06 am
Posts: 1219
Location: NE Minneapolis
you made my point for me theo.

the golf club does *not* flex or deform however it also does not STOP. the conversion of energy occurs where the ball deforms off the face and rebounds, and much of the energy of the swing is retained within the continuation of the stroke.

we need the entire system to come to a near instantaneous dead stop in order to transfer the energy. any energy that does not go into that hard stop is lost and not transferred into the projectile.

again, on boats, the top coat is protective, where the fiber is forming a resilient form for it to be added to. sort of like our metal base. the metal lip is generally a rolled glass edge on larger boats, with the metal only used to protect the exposed edge of the glass.

we have 2 options for glassing really, one is foam the shape and glass over as structure, and the other is build the structure and glass as support.

i do not believe that a layup has the strength to withstand the impact forces on it's own in any fashion. i *do* think that as support for an underlying structure it'd be helpful. however, we're going to have issues attaching a new support structure to the existing spoon without at least slicing into the bowl to place some sort of extension of the throw arm into it, which leads me to think we make the current spoon pretty or leave it as an example piece.

i think that the 3 most reliable options for us are as follows (in no particular order):
-notch, bend and weld steel square stock, welding on two thin steel faces with a lip on the perimiter. this will be a more significant welding and forming project, but a monkey ton of fun as far as i'm concerned. hoot will be bruised from forming the bowls, but she's tough.
-laminate with appropriate glue, a lot more clamps, better steam setup, and better quality wood a beam that is solid throughout, and integral to the spoon head. a fiber sleeve over the shaft won't hurt.
-find a ~1.5" dia fruit wood branch as close to the bends that we need (the near 90 at the neck and curving back) as a natural bend, steam the monkeys out of it, and finesse the last bit, slotting into it either a bent ply or laminated bowl, bound through with large formed washers.


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Tue Mar 17, 2009 7:01 am 
Offline

Joined: Tue Jan 13, 2009 8:26 am
Posts: 378
metis wrote:
anyone have a metal bandsaw?

The shop here in my office does. For a simple item (one or two or three cuts) it would be no problem for me to come in on a Saturday (or evening)(or even do it on a lunch hour or break) and cut up whatever we need cut up.

It's NOT the nice big gravity feed kind, where you put the piece to be cut into a holder, clamp it down, release a screw and watch the nice, liquid-cooled saw slowly chew its way through your stock. It's the flat-table finger-stealer kind that requires the user to hold both halves of the work piece and slowly push it against the blade. Works great, though- I've cut all manner of metal with it, and I have no doubt that it could produce some nice cuts on a piece of, say, square iron tube- although it's worth mentioning that because of the way the device is structured, there's a limit to the size of the workpiece. There's only about 18" of clearance from the vertical support to the blade, so that kind of limits some of your options.

Also, we have a nice vertical milling machine, which can be used to square the ends of the workpiece.

_________________
Mike H.
My maker blog


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Tue Mar 17, 2009 9:15 am 
Offline
User avatar

Joined: Wed Jan 28, 2009 9:53 am
Posts: 928
Location: Eagan, MN
Metis -- don't forget there's that tabletop Ryobi bandsaw of mine sitting in your garage. If it needs to cut metal, a fine-toothed ribbon blade is not very expensive at Home Depot. (It's not useful for my deck work, so I won't need to take it back today, and anyway I got all my lumber ready for that before winter hit.)

_________________
my workplace blog
my builder blog
my personal blog


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Tue Mar 17, 2009 9:45 am 
Offline
User avatar

Joined: Wed Jan 14, 2009 10:06 am
Posts: 1219
Location: NE Minneapolis
what we'd be looking at is cutting... probably 10? v notches into one side or the other of a piece of thin walled ~1" square stock. the point wall would remain, and probably have a target drill hole located in the point a bit wider than a saw blade. angles would need to be pretty exact, but could be marked in advance and noted. a few more than 3 cuts.


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Tue Mar 17, 2009 10:50 am 
Offline

Joined: Tue Jan 13, 2009 8:26 am
Posts: 378
metis wrote:
what we'd be looking at is cutting... probably 10? v notches into one side or the other of a piece of thin walled ~1" square stock. the point wall would remain, and probably have a target drill hole located in the point a bit wider than a saw blade. angles would need to be pretty exact, but could be marked in advance and noted. a few more than 3 cuts.


I could do this, easily. I could even do the holes, using the mill- it would be infinitely easier than trying to do it with a hand drill.

Let's see- the notches should be an isosceles triangle, so the two sides line up nicely. The angle would be dictated by the degree of shape change we want to attain. Hmmm. Anyone have a nice side-view image of the spoon bridge?

_________________
Mike H.
My maker blog


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Tue Mar 17, 2009 10:52 am 
Offline
User avatar

Joined: Wed Jan 14, 2009 10:06 am
Posts: 1219
Location: NE Minneapolis
yup, in DWG already even. will try to sort out cuts later this afternoon if i get a minute.


Top
 Profile  
 
 Post subject: Re: Spoonapult v1.0 the wreckening
PostPosted: Tue Mar 17, 2009 10:56 am 
Offline

Joined: Tue Jan 13, 2009 8:26 am
Posts: 378
Nice. I believe my CAD program (A9CAD) can open a DWG file well enough.

_________________
Mike H.
My maker blog


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 30 posts ]  Go to page Previous  1, 2, 3  Next

All times are UTC - 6 hours


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Template made by DEVPPL Flash Games