MYOG Tunnel Tent - Pole Connector questions
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Aaron Robson
(quintessence)

Locale: Texas, California, BC
Re: straight carbon poles for trailstar on 01/31/2012 20:52:33 MST Print View

Stuart,

I've done a fair bit of research into this when I was looking at pyramid tents - my overall conclusion was that the poles (I found) available on the market don't represent very good solutions for mid center poles.

For a mid pole, you have a fairly long unsupported span that has relatively high axial (compression) loading and almost no bending loads - unless you bump into of course. You want something that is as stiff and light as possible for a given length. Unfortunately, the available tubing tends to be either: thin-walled (light) but small diameter (bendy) OR larger diameter (stiff) but thick walled (heavier than necessary). I think this is because the thick walled tubes are designed to be multi-purpose, and resist both bending and axial loads. My ideal pole would be 0.5-0.8" in diameter, but still with a relatively thin wall.

Roger I believe had a wealth of information about CF manufacturing processes, all of which is very interesting.

Aaron

a b
(Ice-axe)
Pole for Mid on 01/31/2012 21:05:53 MST Print View

Here is what my 15+ year old Choiunard (Black Diamond Pyramid has for a pole.
.Chouinard Pyramid pole
.Chouinard pyramid pole
.Pyramid pole
.Pyramid pole
.
It weighs 8 ounces (Gasp!). You could fight off an Angry griz with it or pole vault the river Nile.
The one thing this pole never did was collapse. Even under some nasty high wind storms and heavy snow loads in excess of 6 inches.

Samuel C. Farrington
(scfhome) - M

Locale: Chocorua NH, USA
Elbows ad nauseum on 01/31/2012 22:02:35 MST Print View

Roger,
Thank you for that response. I note that you have several poles on your design, so that it must take quite a few guys to stabilize them all. But that is what I also see often on European tents used for high winds - lots of guys on the poles.
A while back someone posted a link to a video of a Warmlite tent in high winds without guys - frightful.

About the dihedrals - Just ordered a few and measured them with a protractor. That's where the 30 degrees came from. The kite folks don't seem to think in terms of degrees, so it has become necessary to order and measure. Same with the angled fittings. Makes for great cries of either delight or cursing at the kitchen table. Dearly hope the larger ones I ordered are the same angle as the two little ones ordered first. Expect so.

Aaron,
The size difference between tube and ferrule for both the Easton .344s and .340s is .003". You are thinking about a difference of .006" when the .340 tube is inserted into your carbon tube. Please note Roger's comment, above, about the result of having the tube too loose in a connector.

So I suggest you need a snugger connection, no more than .004" at the most, and ideally, .003".

Also, even if a .344" O.D. tube elbow were available, inserting it inside, rather than over your carbon tube as Roger does, will put a lot of pressure on the lip of the carbon tube. Not so good.

But anyway, I tried cold bending an Easton .344" tube with one of those cheap 3-slot benders that you get from the tool outlet sites ("Pittsburgh - made in China). But the fit was snug, and the tube broke almost as soon as it started to bend. Was in the basement at about 50 degrees F. temp, so will bring a tube upstairs and try again tomorrow at room temp. Will post if that makes a difference. As earlier noted, if I heat it, it will lose the temper - no good for an elbow.

You could talk to a machinist, who might know how to bend the Easton .344 to your desired angle and preserve the temper. Otherwise, the problem is that most of the 5/8" ALU stock, as well as the more tempered but bendable Jansport 5/8" tube, is closer to .4" I.D. than the O.D. of .387". If you drop to 1/2" stock, it is too small.

I guess what I would do, if I wanted a strong elbow and therefore didn't want to play with the softer plastic pipe fittings, would be to get the 9mm (.354") dihedrals , and fill the end holes with high quality epoxy, maybe a putty, and drill them out to .346". Then I would cut 3" inserts of Easton tubing and glue them 2" into the ends of your carbon tube. The protruding 1" should then fit into the dihedrals, and the carbon tubes would be less likely to break because the snugly glued inserts would spread the force over the 2". Sorry I don't have a better suggestion. Consider calling polesforyou.com before making a choice.

Edited by scfhome on 01/31/2012 22:07:49 MST.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Tube fit on 02/01/2012 00:50:08 MST Print View

Hi Aaron

Depends on exactly what material I have at hand.

For CF tube into Easton arrow shaft for straight coupling, 30-50 microns RADIUS clearance.
The inside bore of the easton poles is very smooth, and the OD of the CF arrow shafts are ground to dimension.

For SS elbow machined down into CF tube, hum, about the same.
The ID of the CF tube is very smooth (ground SS mandrel), so the machining on the SS has to be good. A quick polish with fine wet&dry is normal after turning.

Cheers

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: straight carbon poles for trailstar on 02/01/2012 00:54:06 MST Print View

Hi Stuart

Yeah, I'd give that a go. I am assuming you are not trying to handle a storm on the Main Range though!

Ferrules: I would recommend finding an archery shop and seeing what they have from Easton. Be worth trying an Easton 2317 shaft I think.

I would not use pultruded!!!

Cheers

Edited by rcaffin on 02/01/2012 00:54:47 MST.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Elbows ad nauseum on 02/01/2012 02:01:01 MST Print View

Hi Sam

> the tube broke almost as soon as it started to bend.
Chuckle! You can't 'bend' Easton tubing with a conventional tube bender. You have to roll it in small increments.

I have managed to curve 340 or 344 tubing to have a radius of under 6" with little loss of strength, but you need complex rolling gear.

I was fascinated by your suggestion about composite elbows. Yeah, could work. As a matter of fact, I think you could start with larger 6060 Al tubing which will bend in a bender, and then sleeve that down with Easton tubing. Hum ...

Cheers

Stuart Allie
(stuart.allie)

Locale: Australia
Re: straight carbon poles for trailstar on 02/01/2012 03:03:19 MST Print View

Aaron, thanks for that. I agree with what you said - I just can't find any (non-pultruded :) carbon tubing that has a large diameter but fairly thin wall and is available in small quantities. I'll keep looking though.

Roger, I don't know about the Main Range but the shelf camp at Mt Anne in Tassie can get pretty windy (as I'm sure you know!) so I am looking at something *quite* strong...

Taking your advice and ignoring pultruded tubing... how about the 0.319" wrapped tube with a core of 0.240" solid pultruded rod? Basically using the solid rod as internal ferrules with no gaps so I'd end up with an almost solid carbon pole, pultruded on the inside and wrapped tubing on the outside. That'd still be fairly light (somewhere around 100g I think) and pretty strong I think?

I wlll keep looking for some larger wrapped tubing though.

Thanks.

(P.S. the crux pack is wonderful so thanks for that too!)

Samuel C. Farrington
(scfhome) - M

Locale: Chocorua NH, USA
Elbows - Ad noseeum on 02/02/2012 20:36:45 MST Print View

Roger,

Chuckle all you want - the devil made me do it.
After the .344 was warmed up to just above room temp, it actually did bend to about 5-10 degrees, but then still snapped.

Still wonder if a machinist knowledgeable of metalurgy would know how to hot bend the Easton tempered tubing without losing the temper.

Thought about using something akin to your 'rolling jenny,' but decided that an elbow with a 5-6" radius would be quite a bit longer than Aaron would like.

Don't know what those kite dihedrals are made of, but will find out soon enough how strong they are when the order arrives. Need them for a pack frame, as noted before.
The approx. 30 degree angle won't work for the XX tent I'm making. Easton .344s bent to the required 120 degrees would be awesomely better for the tent than the heavier 3/16" Titanium rod cut from tent stakes that I'm using.

About the ALU tubing. Yes - great idea. Saw some 7/16" (11.1mm) 6060T6 tubing on a kite site and ordered a piece. Yes, it will bend nicely with a bender, and probably hold the angle in your application. But don't have a 7/16" bender, so will have to try it with a half inch one, maybe with something to tighten up the fit on the rollers. If that works, will try drilling out the ends of the elbow to fit snugly over the .385" O.D. carbon that Aaron is using. That would produce a fairly light and short elbow that would fit over the tubing, thereby reducing, IMO, the likelihood of failure of the carbon. Stay tuned - there is light at the end of the tunnel (no connection intended with the shape of your tent).

Troy Ammons
(tammons) - F
MYOG Tunnel Tent - Pole Connector questions on 02/02/2012 22:17:53 MST Print View

I dont know if its been mentioned but if you are going to bend aluminum tubing try filling with sand.

I bent some NANOLITE tent poles from Quest by hand into a very tight curve.
Way tighter than straight tubing would allow. Pretty easy really.

It also helps if you are trying to bend tube on a tubing bender. Supports the tubing and helps it hold its round section profile. Sort of like a cheap mandrel.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Elbows - Ad noseeum on 02/03/2012 02:04:00 MST Print View

Hi Sam

> Still wonder if a machinist knowledgeable of metalurgy would know how to hot bend the
> Easton tempered tubing without losing the temper.
To the best of my knowledge, that is simply not possible. It loses its T9 temper not very far above boiling point, or something like that. Note that T9 is actually off the conventional tempering scale: Easton are the only company in the world to be able to do it.

> Saw some 7/16" (11.1mm) 6060T6 tubing on a kite site and ordered a piece.
Plenty strong enough. Go for it, and let's see photos.

> 30 degrees won't work for the XX tent I'm making. Easton .344s bent to the required
> 120 degrees
I had that problem too, which is why I went from 1 elbow to 3. In *addition*, 3 elbows gave me much better headroom inside. 2 elbows is OK for head room but leaves a flat top which is dangerous for snow loading.

Cheers

Edited by rcaffin on 02/03/2012 14:39:56 MST.

Aaron Robson
(quintessence)

Locale: Texas, California, BC
Re: MYOG Tunnel Tent - Pole Connector questions on 02/03/2012 09:51:09 MST Print View

What Troy said is definitely worth a shot - I've seen that technique discussed in a number of different places. Of course, you have to seal the ends of the tube you are bending so the sand doesn't just get pushed out, but it is supposed to give very good results.

Aaron

Daryl Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Re: MYOG Tunnel Tent - Pole Connector questions on 02/03/2012 21:08:59 MST Print View

Aaron,

I don't have a solution that specifically addresses your question. I do have some of the same (or very similar) carbon fiber tubing that you are using, however. Here are a couple of ideas that I offer as food for thought. They may trigger some better ideas from some of the other members.

Here's a post that shows how I used these poles for the fly shown in my avatar.

here

And here's an external elbow I just bent that fits the tubing. I used some scrap aluminum tubing that is OD about .5 and ID about .4. The fitting weighs .5 ounces. It was easy to bend with my tube bender.

here

Daryl

Samuel C. Farrington
(scfhome) - M

Locale: Chocorua NH, USA
bending with sand on 02/03/2012 22:27:23 MST Print View

Troy,
OK, the Nanolites are the Easton .344s, on the Quest website.

Wondering what 'very tight' is before I go snapping more tubing.
Suspect you must have bent it over a cylindrical form. Wondering what diameter or radius you used for the form. (Was thinking of a tire for some high radius bends I need to make for a pack frame.)

The Quest elbows have a 2.5" radius for a 90 degree bend. Anywhere near that tight?

Would appreciate your advice on these points.
Thanks.

Samuel C. Farrington
(scfhome) - M

Locale: Chocorua NH, USA
pole breaks at connectors on 02/03/2012 22:52:39 MST Print View

Daryl,
Scroll back a few posts and read Roger's comment about loose fitting connectors and carbon.

A couple years ago, I did a slew of break tests on every wrapped carbon tube I could get my hands on. Bet you can't name one that I left out. While I was very careful to put the same pressure on each sample, and the results were good enough to steer me to the right carbon tubes (see Roger's post on that above, also), the results were not reliable from a scientific point of view.

The reason? The closeness of the fit of the connector over the carbon tube had to be exactly the same, or the results would vary substantially, even for the very same tubing. The snugger the fit, the higher the break point (pounds of force required to break) - much higher.

At one point I thought I had found the miracle tube, until I realized it was just because I was using a much tighter connector tube over the test piece. It was not possible to address this problem fully, because i did not have connector tubes to fit every piece of carbon tube with exactly the same amount of snugness. But finally got the tests uniform enough to determine that the Victory 300s were 20-30% stronger than most other carbon wraps, like the Sky Shark, and gave the best strength for weight. A lot cheaper too, BTW.

Using a .4" I.D. connector over a .385" O.D. tube would be pretty loosy goosy. Much more likely to break under stress than with a snug fit. It helps to have tube and connector materials with the same flex ('modulus of elasticity'), and to use external connectors that go over the ends of the carbon tube and protect them; but the loose fit is a killer.

Fortuitously, about the same time I found the Victory 300s, I also found that the Easton nanotubes, or .344s, fit over them with just the right amount of snugness - no detectable wobble, but no difficulty with insertion. It is necessary to make sure the connections are clean of dirt and sand before connecting, but that is true of any tent pole; and as with most BPL stuff, the little bit of extra care is the price we pay for the ultra light gear.

Edited by scfhome on 02/03/2012 22:58:01 MST.

Samuel C. Farrington
(scfhome) - M

Locale: Chocorua NH, USA
ALU tube and Dihedrals on 02/03/2012 23:40:53 MST Print View

Roger,

No sooner was the 7/16" tubing ordered, than the kite company put a message on its machine that orders will be delayed due to an illness in the family. So it may be a while before there is anything to post. Ordered some custom drilled hubs from the same outfit before Christmas, and they are still outstanding, so now will have to drill one out myself from some hub blanks I got way back from Fibraplex. Have only two to work with, so only one mistake allowed. What fun.

Got some 6mm excel dihedrals from Goodwinds, though. Molded plastic, but very sturdy, with plenty of room to drill out for .24" (6.1mm) carbon rod for the pack frame. They weigh .23 oz (6.5gm), though, a little heavy, but only need to use two of them. Probably too heavy for tent pole use, but just FYI, each end takes 2.5cm of tube/rod. The 8mm ones, large enough to drill out for .295" tube would be even heavier.

Cheers.

Stuart Murphy
(stu_m) - MLife
Re: Elbows ad nauseum on 02/04/2012 00:45:56 MST Print View

Polesforyou.com will bend Easton tubing bought from them up to and including 13mm diameter.

The poles are pretty reasonably priced... don't know why you'd want to muck around with it as DIY.

Woops, sorry, just realised you're talking about bending aluminium for use as elbow connectors... please disregard post

Edited by stu_m on 02/04/2012 00:50:18 MST.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: ALU tube and Dihedrals on 02/04/2012 01:47:17 MST Print View

Hi Sam

You ought to be able to buy suitable tubing from many places. Try Mcmaster Carr for instance.
(Sulk- they won't export to me. Export regs are now so complex they don't make a profit any more on export orders becasue of the paper work. That's the USA Govt helping American industry.)

Snug fits - YEAH!
However, if you get some snug-fitting Easton arrow shaft which fits over the CF tube, you can epoxy a short length over the end of the CF tube to *help* reinforce it. It might help prevent what you can see below. (I had better add, that pole was not on MY tent! The damage was due to misuse.)
CF pole damage

Cheers

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: ALU tube and Dihedrals on 02/04/2012 05:28:06 MST Print View

One trick I picked up from building fly rods was to wrap the connection with fine thread. Then use heated (gently heated) epoxy over the threads to hold tension. This adds a bit of pre-load from the tight thread wrap. It will add a gram or two of weight but also adds a LOT of reinforcement to the ends of the poles. About 3-3.5 times the diameter of the tube, down is a good compromise between strength and weight for the connector. I believe they use similar techniques to make barrels by heating a band, pressing to quickly over the wood and letting it shrink.

Looking at Rogers pic, the connector is really too short. The ends should also be sanded smooth as in the pic. You can see the miltiple layers of delamination. Thread wrapping helps prevent that. Epoxy makes it smooth for easy insertion into whatever.

Daryl Daryl
(lyrad1) - MLife

Locale: Pacific Northwest, USA, Earth
Re: pole breaks at connectors on 02/04/2012 09:38:06 MST Print View

Samuel,

Thanks for the info. I had noticed the snugness comment from Roger and your experience really amplifies the importance of it.

I'll keep the Victory 300s in mind for future projects. Been using Skysharks. There have been some good deals on Skysharks lately. That's how I ended up with the .385" od stuff.

My primary aim in making the elbow was to see how difficult it would be to make one for .385" od tubing. I concluded that it was easy. One just needs to get the right size of tubing and make sure it can be bent.

Back to the snugness factor. I wonder if snugness can be fine tuned by wrapping the carbon fiber tubing with something like foil or teflon tape?

The .385" od carbon fiber tubing also fits into the black nylon 1/2" od barbed plumbing fittings I bought from McMaster-Carr. It only goes in about 1/2", however, so I couldn't see an application to this thread.

Daryl

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: Re: ALU tube and Dihedrals on 02/04/2012 14:02:36 MST Print View

> Looking at Rogers pic, the connector is really too short.
Well, that depends very much on the quality of the fit. My own experience is that with a snug fit that length of connector is just fine and has lasted for maybe 8 years of heavy use with zero damage (on my tents).

The connector in the photo was broken by gross violence at the bend by someone else. I really don't think one should infer anything about the connector length from that case.

Cheers