GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: rsterne on November 02, 2019, 04:21:19 PM
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I just ran across a source for a huge variety of Carbon Fiber tubing in Metric sizes.... Here is an index to what is available (scroll down)….
https://www.ebay.com/itm/134143296862?var=433589556806 (https://www.ebay.com/itm/134143296862?var=433589556806)
Click on the size you want, you can buy singles or multiple quantities.... and the shipping is very cheap.... They appear to be in inventory in California China....
Bob
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That’s nice. I’m getting a headache trying to convert measurements though. Lol
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Been purchasing that Chinese CF tube for a few years now. Actually the quality is first rate ( cosmetics wise anyways )
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I have been as well, Scott.... but just found this supplier, with an easy-to-follow index.... and low shipping prices....
Bob
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Mr. Sterne,
With your permission, I have another vendor to recommend.
I am not a fan of the checkerboard pattern of carbon fiber tubes and found pultruded carbon fiber tubes. The vendor of the size I needed was on Amazon. Initially they sent me the wrong size. When I let them know they quickly responded that they would cross ship the correct sizes and send me a prepaid return label for the wrong tubes. Not many vendors cross ship anymore. The vendor was "Truly Exceptional Products"
Here is the listing I bought:
https://www.amazon.com/gp/product/B07KWFX135/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1 (https://www.amazon.com/gp/product/B07KWFX135/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1)
The carbon fiber strands run the length of the tubing and that is supposed to make the tubing stiffer to flexing than the normal cf tubing. The finish is a semi gloss. I have attached pictures. The ones with flash show how the strands run. They look like scratches but they are not and just exaggerated by the flash.
I hope this wasn't considered a thread hijack. If yes, I apologize in advance, and I can re post in a new thread.
I just thought it was another good option.
Taso
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I just ran across a source for a huge variety of Carbon Fiber tubing in Metric sizes.... Here is an index to what is available (scroll down)….
https://www.ebay.com/itm/Glossy-20mm-OD-14mm-ID-1000mm-Length-3K-Roll-Carbon-Fiber-Tube-20-14-1000/283042432313?hash=item41e6a4c539:g:VVUAAOSwfgBdIxF7 (https://www.ebay.com/itm/Glossy-20mm-OD-14mm-ID-1000mm-Length-3K-Roll-Carbon-Fiber-Tube-20-14-1000/283042432313?hash=item41e6a4c539:g:VVUAAOSwfgBdIxF7)
Click on the size you want, you can buy singles or multiple quantities.... and the shipping is very cheap.... They appear to be in inventory in California....
Bob
ive bought from him before. the glossy finish is really impressive and the price is right
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Unidirectional CF tubing is a bit stiffer in longitudinal bending than the tubes with the woven fabric in the outer layer, on a same diameter basis.... I am quite familiar with CF tubing, and all the grades of CF and the construction, as I spent 30 years doing R/C model racing yachts.... In fact, at the 1980 World Championships we were the first to use a material which at that time was called "Pitch Fibre", and is now know as "Ultra-High Modulas Carbon Fibre" for masts.... There are now 4 grades, explained in this quote from Rockwest Composites....
Carbon Fiber Material: Modulus, Strength | Benefits, Features & Notes
•Standard Modulus | 34 msi, 700 ksi | Good structural properties - Stiffer than aluminum - Readily available
•Intermediate Modulus | 42 msi, 825 ksi | Great structural properties - Highest strength option - Great balance of stiffness and strength
•High Modulus | 57 msi, 670 ksi | Very stiff - Good thermal conductivity / stability - Typically used in all 0° & 90° (or off-axis) plies throughout the ply sequence / laminate orientation.
•Ultra High Modulus | 94 msi, 414 ksi | Stiffest option available - Great thermal conductivity - Used primarily as 0° plies in combination with lower modulus / higher strength fibers in the 90° orientation to create a well-balanced and functional composite structure.
As with most materials, there is a trade off in properties.... The stiffest material is also the weakest.... However, for barrel sleeves we don't care about strength, only stiffness.... One problem for those not living in the USA is that the UHM fibre is subject to the ITAR rules, and you may need a special permit to export it from the US.... ::)
The values given above are for the pure fibre, in the direction of the fibre strands, and do not take into account the resin matrix.... Steel has a modulas of 29-30, which would lead you to believe that even the standard CF tubing is stiffer, but in fact that is not the case.... Standard CF tubing is stiffer than aluminum tube, but not a stiff as a steel tube of the same diameter.... A tube made from UHM fibre, on the other hand, is stiffer than the same size steel tube....
The common CF tubes with the woven finish only have that fabric on the very outer layer.... It is basically to improve the appearance.... The majority of the layers in the tube laminate, typically 60-70%, are the same unidirectional CF that is used in a pultruded tube.... You would think that would give a significant edge to the stiffness of a pultruded tube, but in fact there is a higher resin content and lower fibre content in most pultruded tubes, because of the way they are manufactured (extruded and pulled through a die)…. The "roll wrapped" tubes have the unidirectional and woven layers (pre-impregnated with resin) wrapped around a mandrel and then compressed by an outer vinly wrap which presses the layers tightly together, and then they are cured in an oven using heat.... Generally, roll-wrapped tubes have a lower total resin content than do pultruded tubes, which are only about 60% CF by volume.... Pultruded tubes are generally made as a low-cost alternative, where hoop strength (to avoid crushing or collapsing on bending) are not an issue....
The primary factor in the stiffness of a sleeve on a barrel is the outside diameter.... The stiffness varies with the 4th power of that.... ie double the diameter and the stiffness increases by 16 times.... The modulas of the fibre is the next most important, a UHM tube may be about twice as stiff as the same diameter standard CF tube.... While a uni-directional prepreg layup may be a bit stiffer, I have my doubts if a pultruded tube is.... It probably depends on the manufacturer....
Bob
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Uni is always stronger in tension using the same fiber as woven. Bob is correct. a 60% to 65% fiber volume is the optimum in strength. A uni will give very high tensile but poor compressive strength that's why you need either a woven material or a 0/90/+ and - 45 fiber orientation that is balanced from the center of the laminate out such as 0,90,+45,-45,0,-45,+45,90,0 for a 7 ply laminate. I layed up some T beams for a composite wing we were making for Nasa using stitched RFI for the main wing uppers and lowers. The Boeing engineer that came up with the ply orientation table was off by only one ply. The beam had a curve to it and had the engineers thinking we plied it up wrong until I pointed out that the ply table was unbalanced. I'm the geek wearing the hat. lol
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Grey hat White shirt ... or, Grey hat Grey shirt ?
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Since this thread got off on a bit of a tangent (and I'm fine with that)…. here is a chart (from the Rockwest Composites website) showing the advantages of various types of CF tubing....The "Roll-Wrapped" tubes we are most familiar with, are made over a mandrel, so they are represented by the yellow line.... "Pultruded" tubes are shown in grey, and "Filament Wound" tubes are in orange.... The newest manufacturing method, called "Pull-Braided" is shown in blue as "CBC" (continuous braided composite).... The exact properties of any of these tubes will depend on the fabric layup used.... For example, a uni-directional "over mandrel" tube will be stiffer in bending than one with a fabric outer layer.... but that will likely still be better than a pultruded tube of the same size....
(https://i378.photobucket.com/albums/oo221/rsterne/Important/Differences_Of_Pullbraided_zpsczznazqr.jpg) (http://s378.photobucket.com/user/rsterne/media/Important/Differences_Of_Pullbraided_zpsczznazqr.jpg.html)
Pultruded tubes are the cheapest, but are not as good in bend (flexural properties) as Roll (Mandrel) Wrapped.... Filament wound tubes are primarily used to resist torsion (twist), and are the poorest in bending applications, because most of the fibres are on the bias (45*).... Buckling stability, hoop compression and torsional performance are not important for barrel sleeves.... The only important property (other than cost) for barrel sleeves is bending (flexural)…. The new "Pull-braided" tubes are even better than a Roll-wrapped tube in bending, and lower in cost.... so when they become more widely available, they will be a good choice.... The stiffest barrel sleeve would be a uni-directional mandrel wrapped tube made with UHM (Pitch) fibre, of course.... at about twice the cost.... :o
Bob
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Thank you Mr. Sterne and Mr. Robert! I learned something new today. Thank you for the diagram in your last post. It helps a lot!
I thought since the pultruded carbon fibers were basically going in the same directions along the length, like trees and lumber, that they would be stiffer to bending. So that stiffness would help us in stiffening our barrels.
But I am a little confused. Are you gentlemen in agreement in your initial posts? :o
Thank you,
Taso
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Pultruded has the correct fabric orientation (axial) to produce the best stiffness.... However, Roll-wrapped tubes, made with Pre-preg epoxy on a mandrel.... have the fibres glued together better, and even though they have fewer fibres running lengthwise, they perform better, at least according to that chart.... Pulltruded are much cheaper, however.... The thin woven fabric outer layer (in a roll-wrapped tube) has uni-directional fibre immediately under it, and each layer is about 0.006" thick, plus half the outer woven layer is also running lengthwise.... so the better gluing of the fibres together more than makes up for the few additional fibres running lengthwise in a pultruded tube of the same size....
Pulltruded tubes are good as barrel sleeves.... particularly since they are cheaper.... I have never seen any made with high-modulas or ultra-high-modulas fibre, probably because there seems little sense to use an expensive material in a cheaper product....
Bob
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Thank you Mr. Sterne!
Taso
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Grey hat White shirt ... or, Grey hat Grey shirt ?
Grayish hat white lab coat.
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How do you deal with the taper in mandrel made? Inside diameter.
find it a pain but in short sections ok. I waste more than I use. It's a bugger to turn but the best.
It's a new to me material so my views and suggestions should be taken with a pinch.
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The mandrel is straight, and produces tubing that is constant inside diameter from one end to the other....
unless you purchase tapered tubing, of course (like a fishing rod)….
Bob
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Unless it's a room temperature cure you use aluminum for the mandrel which when you heat it expands. The resin system then sets at the expanded dia. Then when it cools the mandrel shrinks back to original size allowing it to be with drawn from inside the tube. For room temperature cures you would need a very shallow draft or taper to be able to get the mandrel out. Use heat shrink tape to apply pressure.
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Would it be unreasonable to use a pultruded inner sleeve with a mandrel wrapped outer sleeve and bond the two sleeves together?
What glue or resin would be optimal?
Hunter
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The very outer layer is the most important in terms of the stiffness imparted to the barrel.... The larger the OD, and the stronger the fibre, the better.... Nothing wrong with using pultruded as the inner layer because it's cheaper.... I have considered using stepped layers of CF tubing to replicate a tapered barrel, but not done that yet....
I use Loctite 638 to glue the sleeve to the barrel, I suppose you could use it between sleeves as well.... It isn't really intended for plastics (which is what the resin in the CF tube really is)…. but with a post cure to hurry it up it bonds CF to steel just fine.... I use 175*F for 3 hours, after first allowing a room temperature cure for 16-24 hours.... You could also use an Epoxy resin, but it need to be a thin viscosity because the gap is likely to be quite small.... I have heard Acraglass is good, but never used it myself.... You should sand the OD of the inner tube and the ID of the outer one to give it some "tooth" and get rid of the gloss finish....
Bob
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I have updated the link in the first post, as the one in there was dead.... The new one has an Index of available sizes if you scroll down the page....
Bob
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Another link, this time from AliExpress in China, with an index....
https://www.aliexpress.com/item/1005004160356196.html?spm=a2g0o.productlist.0.0.3c587c091pRqD7&algo_pvid=c1b19185-d2bc-4ef6-9f0c-1635b988d724&algo_exp_id=c1b19185-d2bc-4ef6-9f0c-1635b988d724-6&pdp_ext_f=%7B%22sku_id%22%3A%2212000028234246464%22%7D&pdp_npi=2%40dis%21EUR%217.97%217.97%21%21%21%21%21%402101d91e16639263300068140e9721%2112000028234246464%21sea&curPageLogUid=dWV3VXXucsUv (https://www.aliexpress.com/item/1005004160356196.html?spm=a2g0o.productlist.0.0.3c587c091pRqD7&algo_pvid=c1b19185-d2bc-4ef6-9f0c-1635b988d724&algo_exp_id=c1b19185-d2bc-4ef6-9f0c-1635b988d724-6&pdp_ext_f=%7B%22sku_id%22%3A%2212000028234246464%22%7D&pdp_npi=2%40dis%21EUR%217.97%217.97%21%21%21%21%21%402101d91e16639263300068140e9721%2112000028234246464%21sea&curPageLogUid=dWV3VXXucsUv)
It looks like they are all 1mm or 2mm wall, however....
Bob