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Balor
recumbent guru

Russia
991 Posts

Posted - 11/22/2019 :  01:03:37  Show Profile  Reply with Quote
I want to make prototype of my velo spaceframe from thin cromoly tubes (found local source, relatively cheap).
I don't weld - have neither facilities nor much desire to acquire skills.
I've already experimented with making a simple 'lug' from CF and 3d printed dissolveable mandrel, it works.

Obviously, making a lug of CF is not a very good idea - dissimilar CTE, carbon actually have negative CTE.
Glass fiber is better, but still pretty low.

Basalt fiber, though, have CTE very similar to steel and I have a bunch of it:
https://www.basaltft.com/hist.htm
I suppose that should work, given good, 'ductile' epoxy and proper surface prep?

warren
human power expert

USA
6560 Posts

Posted - 11/22/2019 :  09:10:32  Show Profile  Visit warren's Homepage  Reply with Quote
Seems like a good material. How well does it form to complex shapes? Glass fiber woven fabric forms very well, but CF is much stiffer so it's harder to work with.
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Balor
recumbent guru

Russia
991 Posts

Posted - 11/22/2019 :  09:44:17  Show Profile  Reply with Quote
Not great, not terrible - a bit stiffer than glass. I have a bag of 12mm long chopped fibers, that should do it I think + a few meters of cloth.
I think I'll do it like this (needs experimenting though):
Wet out a 'sheet' of scattered chopped fibers on a plastic sheet (and a few more layers of cloth to be sure), wait to partial vitrification, lay out this tacky mess over the mandrel, peel away the plastic, put under hard vaccum, than shove it into an oven at about 80C to reverse vitrification as in - turn it back into viscous fluid, kinda like short lived OOA prepreg.
I'll be using a packet sealer and food bagging bags to make 100% sure vaccum seal will stay unbroken during cure.

Should minimise my exposure to epoxy and make things less messy overall.
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Speedy
recumbent guru

USA
950 Posts

Posted - 11/22/2019 :  12:22:16  Show Profile  Reply with Quote
Every time I've built a bike there was something that needed changing.
There always is so much to learn about the bike.
Don't get stuck learning a new assembly process that ultimately won't enhance the final product.
Fiber cloth wrapped connections are known to work with bamboo, carbon and aluminum tubes.
Fiber cloth wrapped steel should work equally well.
3D printing takes time. Each lug takes 1 hour to print, 1/2 hour to clean, 1 hour to lay up, 1/2 hour to bond to a tube etc, etc.
Going straight to a wrapped connection will reduce the time to a finished project by probably 75%.
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Balor
recumbent guru

Russia
991 Posts

Posted - 11/22/2019 :  14:35:20  Show Profile  Reply with Quote
quote:
Originally posted by Speedy

Every time I've built a bike there was something that needed changing.
There always is so much to learn about the bike.
Don't get stuck learning a new assembly process that ultimately won't enhance the final product.
Fiber cloth wrapped connections are known to work with bamboo, carbon and aluminum tubes.
Fiber cloth wrapped steel should work equally well.
3D printing takes time. Each lug takes 1 hour to print, 1/2 hour to clean, 1 hour to lay up, 1/2 hour to bond to a tube etc, etc.
Going straight to a wrapped connection will reduce the time to a finished project by probably 75%.



I've heard a lot of cases when aluminium delaminated from carbon... but it has double the CTE of steel, so I guess I could be safe even with carbon, but this bike will not be light anyway, and I don't want to waste it - especially if I'll have to redo stuff - all too possible... I'll try to do preemptive accembly using 'tack gluing'... maybe with hotglue.

I agree about simply wrapping the joints, but that would require jigging and, preferably, mitering. Even 3d printed 'jigging' like Spidermonkey did take time and plastic, and I daresay moreso than my mandrels that are printed with minimum material.
Plus, much more messy and cannot be vacuumed (though can be shrinkwrapped, of course).

Lugs extracted from geometry are "self-jigging", in theory allowing one to create the bike like a lego puzzle - idiotproof (which is sorely required in my case).
If I'll ever get myself a proper workshop with a jig... but all in good time. I am trying to extract maximum fun from the process - going stright to the most optimal solution is actually counterproductive in this case :).

Cleaning up after layup is more like 1 day, btw, but it can be done in bulk - just plop them into the solvent and fish them out a day later, give it a light sand and it's done.
As for bonding - tube prep is exactly the same, but otherwise you cover the tube in thickened epoxy, push the tube into the lug and call it a day. My printer, unless I print too fast, makes very repeatable geometry (though it did develop some strange knocking noises recently, gotta give it a check).

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SpiderMonkey
recumbent guru

USA
725 Posts

Posted - 11/23/2019 :  07:38:51  Show Profile  Reply with Quote
quote:
Each lug takes 1 hour to print, 1/2 hour to clean, 1 hour to lay up, 1/2 hour to bond to a tube etc, etc.
Going straight to a wrapped connection will reduce the time to a finished project by probably 75%.




In most cases, I think that would be true, and off course you and others on this board have forgotten more about building bikes than I'll ever know...

I'm using negatives to make interior lugs with cheap bladders -- inner tubes for now, going to try surgical tubing with a Schrader in one end for smaller tubes next. Well, I've made one so far. Despite doing a lousy job laying it up, it came out really dense and really stiff, seems it will be superior to the wrapped bends I did on my first steering tiller assembly.

I'm going to make steering with these first, and then try them for my space frame seat, and if it goes well, I'll likely use them as part of the main bends on the next SWB.

Cons:
To print, my small molds take 6-8 hours for both sides, the large ones take more like 12-16. I just run them at night at work. Since I fixed the spool feed on the printer at work, it no longer fails or requires supervision.

Definitely takes some time to cut the fabric for layup, wet it, and wind it well over the bladder.

Can be tough to remove the bladder sometimes, though I've never gotten one stuck yet, and usually I just stretch the tube and it pulls right through.

Cleanup on the interior lug after de-molding takes some time, but not too bad. Since my tubes do vary slightly on ID (though they're impressively consistent overall) the opportunity to sand them to fit is another way to look at it. As a note, I have found I don't need any release agent, because I can just put a layer of cling film lining the mold, and it works perfectly.

Pros:

Faster with repeating join geometry? I think so. My space frame seats require something like 12-16 of the same 45 degree-to-45 degree join. By making that an entire, smooth, 90-degree bend, I am sure I'll reduce time for that particular case. My experience wrapping those fiddly-little joins is that they're not easy to wrap well.

Faster join with multiple-tubes and acute angles? I think maybe. Related to above, my experience with wrapping spots with 3 or more tubes in close proximity is that it's tough to get a nice compressed composite. Whether using just plain tow Calfee-style or fabric and trying to conform it to the lines of expected forces, it's been hard and very time consuming to get those right, both in layup and in cleanup.

Stronger Join? I think so. My plan is to bond inside, then lightly wrap outside. I'd rather have the join lapped on both sides, especially with the inside lug made of well-compressed fabric custom-tuned for the direction of forces (when applicable).

Nicer looking join? Probably. Depends on one's artistry with the wrapped lug and how much one cares, if at all.

The big one for me is: Perfect alignment on tube bends and angles, with minimal work. I probably spend an hour or more on important bends with my jig(s) making sure everything is as straight as I can make it. Even then, I've had to take some joins apart and redo. And HOLY CRAP is super-glue strong in a simple butt-join on mitered CF tubes. I couldn't actually crack a bond-line loose, and had to cut the tubes apart.

A final one for me is that I am very close to zero-waste on my tubes with my design, meaning that I have it such that the 500mm stock length I get is entirely used up -- so if I cut wrong, or I want the bike to be 2cm longer, I'm out of luck. With lugs for some of my joins, I conserve some stock tube, or I get a free 2cm or so per tube which is helpful for me, especially since the last "500mm" tubes I bought came in at about 496...

I'm lucky in that I've got access to a decent 3d printer for free, and I'm also doing things for fun, so wasting time and learning what doesn't work (or doesn't work well enough to be worth the time) is OK.

If I were prototyping or making version one, I'd just wrap -- and I'd probably choose water-activated polyester-based resin and glass, or broken-bone casting material, such as everyone seems to use for bamboo bikes now.

--SpiderMonkey

Edited by - SpiderMonkey on 11/23/2019 07:54:12
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carolina
human power supergeek

USA
1373 Posts

Posted - 11/23/2019 :  08:27:53  Show Profile  Visit carolina's Homepage  Reply with Quote
First problem. Choose the hysol you needed and forget epoxy.



Get your free aircraft spruce catalog:


———————-
I would not use basalt.

I would also use carbon tubes in structure area from ebay. Rockwest has carbon tubes.

I built this full carbon lowracer with hysol.

https://youtu.be/Kn51U1-RDjc
____________

velosRus.com
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Balor
recumbent guru

Russia
991 Posts

Posted - 11/23/2019 :  10:19:22  Show Profile  Reply with Quote
quote:
Originally posted by SpiderMonkey
Pros & Cons



Excellent post, I agree on all points.
Can you describe how you did your bladder-formed lug, btw?

And can you elaborate on water-based resins and 'broken bone casting'? Sounds interesting.
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Balor
recumbent guru

Russia
991 Posts

Posted - 11/23/2019 :  10:26:40  Show Profile  Reply with Quote
quote:
Originally posted by carolina

First problem. Choose the hysol you needed and forget epoxy.
I would not use basalt.

I would also use carbon tubes in structure area from ebay. Rockwest has carbon tubes.



Well, I agree that for a 'final build' that is certainly preferable, but that is quite expensive, and this is only a prototype that may or may not work out at all.

If everything works as intended, I'll surely buy carbon tubes, use carbon lugs, and specially formulated adhesives instead of diy (I have special epoxy with 'carbon nanofibers' which I suspect really carbon black, but it still supposedly gives epoxy superior performance as adhesive, plus fumed silica of course.)
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carolina
human power supergeek

USA
1373 Posts

Posted - 11/23/2019 :  11:00:51  Show Profile  Visit carolina's Homepage  Reply with Quote
BALOR: Wish you had bunch of pics for deplorable amateur like me. Your builds could help alot of people. Try photo bucket. Nice people and drew always answers email questions.
——————

velosRus.com
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SpiderMonkey
recumbent guru

USA
725 Posts

Posted - 11/23/2019 :  12:48:44  Show Profile  Reply with Quote
quote:
Originally posted by Balor

quote:
Originally posted by SpiderMonkey
Pros & Cons



Excellent post, I agree on all points.
Can you describe how you did your bladder-formed lug, btw?

And can you elaborate on water-based resins and 'broken bone casting'? Sounds interesting.



Here's Calfee wrapping a bamboo bike. They used to use epoxy and hemp string, or CF tow, but he likes this better now. https://youtu.be/-eHxrsqP7gE

This is just fiberglass casting tape, water-activated poly resin over glass. You get maybe 5 minutes to wrap. Cheaper to buy it 4" wide and cut it in half. Such as: https://youtu.be/-eHxrsqP7gE

I've never used it, but it would make a decent thing to take on a tour on any bike, since you could splint a bone, metal, or CF frame if you needed to. Also seems like a good prototyping joint-wrap.

My first, test lug:



That's after trimming. Here, nested inside the 22mm OD / 19mm ID I'm going to use for handlebars next time around:



Here, being made, none too well. I tried to lay the wetted CF into the mold, then put the inner tube bladder in on top, then sort of overlap the layers, then put on the top half of the mold, and it was a bit too much to fit nicely in the 19mm diameter. Also, I used overlapping squares for each side of the bend instead of just a long continguous piece because I was worried it wouldn't conform well to the bend. It would have just fine. This one is 1 layer 9 oz uni + 1 layer biaxial 45/45, 9 oz, plus a layer of 6 oz weave.







Next time, for these thin ones, I'm going to try using a smaller bladder (hopefully surgical tubing with a schrader shoved in one end axially), and I'll roll the layers on it like rolling paper on a core, then put in mold and inflate slowly. I think it'll expand nicely enough. We'll see.

This one, which I thought I'd have to toss aside, will work just fine for 'bent tiller steering.

--SpiderMonkey
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SpiderMonkey
recumbent guru

USA
725 Posts

Posted - 11/23/2019 :  16:02:35  Show Profile  Reply with Quote
Carolina, I love that build. Your stuff is always interesting and makes so much sense. I've seen you make a lot of those square tubes, but I don't remember if I've seen how/what you use for layup, fiber orientation, etc. From the photos everything there seems to be 3k or 6k twill on the outside? Inside?

--SpiderMonkey
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carolina
human power supergeek

USA
1373 Posts

Posted - 11/23/2019 :  17:11:37  Show Profile  Visit carolina's Homepage  Reply with Quote
I have few vids on my deplorable amature channel:)

7 ounce, 11 ounce twill, uni down in both sides of mold.

1) i pulled 3 piece mold from aluminum tube 40mm
2) u see these two booms i made on yellow and the 4 wheel velo.
3) bought bladder from piercan near San Diego.
4) cervelo contractor in Los Angeles taught me how to build valve. I made half and machinists made other half.
5) 2 part mold bolted together, epoxy runs out both ends into buckets.
6) i have clear lexan angle clamped to end opposite vale.
7) bout 12 to 15 lbs. all night .
8) i use slow epoxy.
9) i have a oiless comercial vaccum for the following morning to suck down the bladder.
10) i use mclube 507 bladder release agent.

What i was taught buy airplane friend in Oklahoma:

1) the lay up, doesn’t take alot of layers. I ran bafangs and other cranks on these booms and tried to break something. It want.
2) two clam shells.
3) clam A (the mold part a) after mavcoat release lay carbon just up to split of mold.
4) clam B (the mold part b) lay carbon in it but let it lap out on both sides as it will reach the top inner of carbon on clam A.
5) lay coated (5 times) bladder into clam B, fold carbon over the bladder.
6) put A on top of B and bolt together/set pressure.
7) your valve is in one end.
8) make your 2 part mold longer than needed in my case.
9) next morning vaccum out your bladder wash in hot soapy water & hang vertical. Wash again before using again and adding your mclube.
10) clean your mold.
11) theres a post on here somewhere year or so ago.

—————————-
LMAO, heres the first one i ever made. This is still laying on coffee table and beautiful, strong too. Nowdays with mavcoat release it practically falls out. This mold is 1&1/2” x 1&1/2” five feet. Other mold is shorter/45”.

https://youtu.be/P25gYPUqtB8

—————-
Heres the window to see bladder and so it want blow up and also so the epoxy can run out in bucket. Bolts and clamps/alot.


______________

velosRus.com

Edited by - carolina on 11/29/2019 20:52:36
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carolina
human power supergeek

USA
1373 Posts

Posted - 11/23/2019 :  17:35:09  Show Profile  Visit carolina's Homepage  Reply with Quote
Heres making the mold, painted and polished aluminum tube.



Overhead of mold and cone shapped valve. It pinches in the bladder and works great.



Heres my VACCUM:



____________

velosRus.com
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Speedy
recumbent guru

USA
950 Posts

Posted - 11/23/2019 :  19:58:12  Show Profile  Reply with Quote
A 3D printed internal lug for jigging up the frame could be a valid short cut.
Glue the 3D plastic lug inside and leave it.
Then wrap the outside with fiber and epoxy as is common.

Again ... when building prototypes it's important to keep the assembly process time as short as possible.
Always seek the shortest path to success.
Get on the road as quickly as possible.


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purplepeopledesign
recumbent guru

Canada
709 Posts

Posted - 11/24/2019 :  13:03:50  Show Profile  Reply with Quote
Variable angle welding clamp

:)ensen.



Those who claim to be making history are often the same ones repeating it.

Video of my trike
http://www.youtube.com/watch?v=MdSLRD_2vzc
Photos of my trike
http://www.flickr.com/photos/purplepeople/
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alevand
human power expert

USA
3726 Posts

Posted - 11/28/2019 :  13:08:23  Show Profile  Visit alevand's Homepage  Reply with Quote
Why not just buy a mig welder and learn to weld. People also braze the joints.

C:
Tony Levand

Edited by - alevand on 11/28/2019 13:10:12
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Balor
recumbent guru

Russia
991 Posts

Posted - 11/29/2019 :  04:02:17  Show Profile  Reply with Quote
Cannot do it in the kitchen, I don't have a workshop, and unlikely any time soon. I can rent a garage to store the velo, but not to use it as a shop.
Plus I just like the idea of using composites (unique strength to weight and form flexibility characteristics), and will only get better, cheaper and easier to work with.
Making a monocoque liner/velo is also out of the question (that doubly require a workshop), but using a combination of vacuum-formed lugs/3d printed mandrels/premade tubes/foam shell seems doable even for a clumsy oaf like me... and I already have a 3d printer (which pays for itself - I print stuff for a modest fee).
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alevand
human power expert

USA
3726 Posts

Posted - 11/29/2019 :  08:54:37  Show Profile  Visit alevand's Homepage  Reply with Quote
You can have one of my fairings, some have a frame already inside. They are much too big for me, 5'7, 135 lbs, but might fit you OK. I can give you details, if interested, maybe shipping to Russia is not so much.

C:
Tony Levand
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Jeroen s
Starting Member

Netherlands
34 Posts

Posted - 11/29/2019 :  09:13:48  Show Profile  Reply with Quote
I don΄t think the proces u describe will work. Once the epoxy gets tacky, u cannot reverse that proces by adding heat, that will only speed up the curing proces even more.

Using a 3d printed plug to keep the tubes in the right positions might be a good idea. i΄d still wrap them with fibremat and then squeeze it out with tape. Adding the short fiberstrands would do nothing for the strengt. I always try to have a back up to keep things in place, if the glue might break. Like an increase in diameter, an iregular form, a bolt true.
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alevand
human power expert

USA
3726 Posts

Posted - 11/29/2019 :  09:24:39  Show Profile  Visit alevand's Homepage  Reply with Quote
The Piranha bike frame is pop riveted aluminum tubing and plate gussets, no welding, and has been holding together for decades..

C:
Tony Levand
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Balor
recumbent guru

Russia
991 Posts

Posted - 11/30/2019 :  10:51:20  Show Profile  Reply with Quote
quote:
Originally posted by alevand

You can have one of my fairings, some have a frame already inside. They are much too big for me, 5'7, 135 lbs, but might fit you OK. I can give you details, if interested, maybe shipping to Russia is not so much.

C:
Tony Levand



That's interesting indeed! But I suspect that shipping will number in the thousands of dollars on top of what you'll ask.
Or... well, people been shipping velos, should work for a liner as well? I can scrape a few hundreds of dollars if I'll ask around.
But aren't those BM liners? I suppose they all don't have any suspension and very limited sight and steering? No point in buying one (even if I'll manage to fit inside, and that is a very big if, I weight almost exactly two times more than you do) if I'll have literally nowhere to ride it...
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Balor
recumbent guru

Russia
991 Posts

Posted - 11/30/2019 :  10:59:15  Show Profile  Reply with Quote
quote:
Originally posted by Jeroen s

I don΄t think the proces u describe will work. Once the epoxy gets tacky, u cannot reverse that proces by adding heat, that will only speed up the curing proces even more.

Using a 3d printed plug to keep the tubes in the right positions might be a good idea. i΄d still wrap them with fibremat and then squeeze it out with tape. Adding the short fiberstrands would do nothing for the strengt. I always try to have a back up to keep things in place, if the glue might break. Like an increase in diameter, an iregular form, a bolt true.



You can, that's how prepregs work actually:
https://www.velocipedesalon.com/forum/f10/diy-prepreg-composite-building-38260.html

Obvously, for 'real' prepregs you need higher temps and pressures, but I guess this will do as well, like I said - I've already tried it and it worked. Obviously, you need a slow curing hardener.
More than that, if you freeze your "prepreg" and continue working in freezing temperatures (since "Winter is coming" (c) we'll have that aplenty), you don't even need to wait until epoxy sets this much, I've tried that as well.

Only problem is making a proper 3D model to extract lugs from, I frankly suck at 3d stuff, makes my head hurt :(.

As for a 'bolt though" that's a good idea, worth adapting.

Edited by - Balor on 11/30/2019 11:01:02
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Speedy
recumbent guru

USA
950 Posts

Posted - 11/30/2019 :  11:33:51  Show Profile  Reply with Quote
Cal Poly bikes were built for ASME competition. (Associate Students of Mechanical Engineers)
Part of the rules, there are 4 riders who change out during the competition. Machines need to be sized for the largest person. At some point in the history of the competition rollover hoops and rider restraints were added to the requirements adding even more size and mass to the designs.
So ... not the best Battle Mountain racers but should be great when adapted to street use.

[/quote]
That's interesting indeed! But I suspect that shipping will number in the thousands of dollars on top of what you'll ask.
Or... well, people been shipping velos, should work for a liner as well? I can scrape a few hundreds of dollars if I'll ask around.
But aren't those BM liners? I suppose they all don't have any suspension and very limited sight and steering? No point in buying one (even if I'll manage to fit inside, and that is a very big if, I weight almost exactly two times more than you do) if I'll have literally nowhere to ride it...
[/quote]

Steve Delaire


Edited by - Speedy on 11/30/2019 11:35:13
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alevand
human power expert

USA
3726 Posts

Posted - 12/01/2019 :  10:03:48  Show Profile  Visit alevand's Homepage  Reply with Quote
Yes, you would have to make bomb bay or fabric doors to put your feet down and hinge the fairing top for access, make a new frame for the Black Stallion fairing. They are BIG, would certainly fit you.. They would need smoother roads too. It looks like the Black Stallion was set up as a fwd tilting trike. The other two fairings are nearly 5 feet tall, Lazarus and Kevlar fairings.

Page 28:
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=2ahUKEwj9x5b16JTmAhURca0KHbUhDLMQFjAAegQIBRAC&url=http%3A%2F%2Fdigitalcommons.calpoly.edu%2Fcgi%2Fviewcontent.cgi%3Farticle%3D1328%26context%3Dmesp&usg=AOvVaw1T3AFQy2XHqTiBO1eXyTnE

kevlar:

lazarus:

C:
Tony Levand

Edited by - alevand on 12/01/2019 10:12:09
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Jerry
human power supergeek

USA
1530 Posts

Posted - 12/01/2019 :  11:22:26  Show Profile  Reply with Quote
Tony, do you think my Baron low racer would fit in one of those shells? I would be interested in buying one from you if I can get one of my bikes to fit it.
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