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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/16/2016 :  14:33:35  Show Profile  Reply with Quote
Just practicing keeping the bead going. Still need more practice. 0.035 is difficult to not blow thru...


Edited by - ShelGame on 01/16/2016 14:40:29
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/17/2016 :  06:19:20  Show Profile  Reply with Quote
I think my Oxy regulator isn't helping me. The lowest gauge reading is @10psi. So, getting it set to ~2psi is difficult. Difficult to read anyway. And, I have to assume the reg can't control as well at that low of a pressure.

EDIT: Just read the Harris specs for the reg I'm using, it should have an output as low as 0.43psi. So, maybe it's just an issue of reading the gauge easily.

Edited by - ShelGame on 01/17/2016 06:55:22
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/17/2016 :  09:14:12  Show Profile  Reply with Quote
I think I had too much fuel flow. Too hot a flame. I am using a Harris #1 tip. I'll try it with a higher pressure next. Everything I've read on bike building sites is to use 3-5psi on both oxy and acetylene. The flame is a little hard to set at this pressure/flow. Definitely better with lower fuel flow, though. Much more controllable flame. No blow-thru's this time. It is hard to keep the right torch angle as you go around the tube. Just have to do about a half inch at a time, move the piece, another half inch, etc.


Edited by - ShelGame on 01/17/2016 09:15:34
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warren
human power expert

USA
6087 Posts

Posted - 01/17/2016 :  11:47:57  Show Profile  Visit warren's Homepage  Reply with Quote
Even though Jerry says its not textbook, that does look much better! If I were you I'd weld up a test part like that and test to destruction to prove to yourself that it is strong enough.
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Speedbiker
human power expert

USA
3744 Posts

Posted - 01/17/2016 :  11:53:04  Show Profile  Reply with Quote
Of course Jerry is right, most guys welding thin steel use a Dillion (DHC)torch. And at those low pressures you need 2 stage regulators to get consistant flow. I don't know what bike builder sites you are looking at, but of all the df and bent frames builders I know, know of, or heard of, only one gas welds frames. Rick Gritters. 99% of the other either braze or TIG. I've never seen or heard of a gas welded df frame. You did beautiful TIG welds on your prone frame. Why not TIG this one?
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/17/2016 :  12:55:02  Show Profile  Reply with Quote
I didn't do the welding on aluminum frame. One of the professional fabricators in the shop I worked in did it. I don't own a TIG. When I used the shop TIG previously (to weld steel), I found it much easier than this.

I only have the 1 miter joint in this frame that I really feel needs to be welded. The rest will be fillet brazed.

I did about 5 more practice pieces this afternoon; progressively better. But, still not real pretty. Or textbook.

I don't really have time for welding school. Or the desire. I don't want to be a master welder of all things. I only need this 1 joint done.

Edited by - ShelGame on 01/17/2016 12:56:27
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Speedbiker
human power expert

USA
3744 Posts

Posted - 01/17/2016 :  13:16:03  Show Profile  Reply with Quote
As that is a high stress joint, can you replace that two tubes with one bent tube? Even if you manage what looks like an acceptable weld, it very likely won't be structurally sound. Or you could weld a mitered sleeve that fits insid the joint, then braze it in. It would look beautiful and nobody would be the wiser. You could make the sleeve by splitting a couple pieces of the existing tubing, and crushing it to a small diameter. The sleeve's sections could be quite short. Just an idea...
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/17/2016 :  13:19:44  Show Profile  Reply with Quote
You read my mind.

I think this is the answer I'm looking for - http://www.cycle-frames.com/bicycle-frame-tubing/NOVA-CRMO-38mm-DOWNTUBE-FOR-MTB-29er-WITH-BEND-NOV_CODT_B38_SHD.html

The angle between my tubes are 18deg, not 15. But, I bet I can work with that piece. I can probably tweak it 3 deg. Braze a sleeve in to extend it to the rear.

Edited by - ShelGame on 01/17/2016 13:27:24
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/18/2016 :  07:33:37  Show Profile  Reply with Quote
Since my welding skill sucks, I've decided to go with a bent tube from Nova, rather than try to butt-weld the miter in the lower tube. The bent 38mm tube from Nova isn't long enough, so I plan to insert a 35mm tube in the short end, and run that up to the headtube. Nova tubes should be here by the weekend.

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Speedbiker
human power expert

USA
3744 Posts

Posted - 01/18/2016 :  12:08:23  Show Profile  Reply with Quote
I just noticed your idler position. I am very sure you will not be happy with it. I'm pretty sure your inner thigh will touch it, over an over. Also, it doesn't appear you have accounted for the chain bouncing around. It is certain to hit your seat and stays, especially in certain gear combinations. Remember, when you aren't pedaling the loose chain moves up and down quite alot.
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warren
human power expert

USA
6087 Posts

Posted - 01/18/2016 :  13:00:23  Show Profile  Visit warren's Homepage  Reply with Quote
I usually just hang a smaller second idler wheel under the big one. I make the smaller idlers from cut down skate wheels.
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/18/2016 :  14:14:20  Show Profile  Reply with Quote
Yeah, I'm still playing with the idler position. That's the reason I got the T-Cycle universal 1-1/2" tube mount kit.

Also, I don't think the sport idler I bought is near that big. I think it's only a 13t (maybe 15t? I need to count).

Edited by - ShelGame on 01/18/2016 14:14:43
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alevand
human power expert

USA
2908 Posts

Posted - 01/18/2016 :  14:27:48  Show Profile  Visit alevand's Homepage  Reply with Quote
Why don't you just bend the 2 tubes yourself, it's only 18 degrees. Fill it with sand and use a big radius block. If it kinks some well then braze or weld the brace there. You can also cut halfway through and bend and weld the top.

C:
Tony Levand
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/18/2016 :  15:48:53  Show Profile  Reply with Quote
Well, I don't have anymore 1-1/2 x 0.035" wall tubing anyway. I'd have to buy more, and then have it bent. If I have to buy more, why not just buy it with a bend already in it? A nice, smooth mandrel bend at that. It's only a few dollars more expensive.

I don't do muffler shop pinch bends. Except on exhaust systems. I'm pretty sure they couldn't reliably make an 18deg bend anyway.
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warren
human power expert

USA
6087 Posts

Posted - 01/18/2016 :  16:32:05  Show Profile  Visit warren's Homepage  Reply with Quote
It looks like that butt joint has a fishmouth crossmember covering half of it. That plus your weld should be pretty strong.
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alevand
human power expert

USA
2908 Posts

Posted - 01/18/2016 :  16:35:20  Show Profile  Visit alevand's Homepage  Reply with Quote
Get a mig welder.

C:
Tony Levand
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/18/2016 :  17:27:07  Show Profile  Reply with Quote
quote:
Originally posted by warren

It looks like that butt joint has a fishmouth crossmember covering half of it. That plus your weld should be pretty strong.



It does. But, I would need a whole lot more practice to get to the level of quality in that weld that I want.

I'll be happier with the bend and reduced OD down tube. Should be lighter, too. Both tubes are double-butted. And now on order.

Edited by - ShelGame on 01/18/2016 18:00:46
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/19/2016 :  06:42:15  Show Profile  Reply with Quote
quote:
Originally posted by Jerry

Muffler shop bends would be way better than your welds! Are you sure you did the lay out? Or did you have someone do the lay out for you? It took 15 years on your first bike, and someone else did the welds and lay out. Just wondering!

I hope you have learned a valuable lesson here. You should practice welding on scrap, not what you are building!




Thanks for the lesson, but I did practice on scrap. I'm not dumb enough to think I can pickup a (new) torch for the first time 15 years and think I'll just get it all done on the first try.

A half caved-in muffler shop bend is no better than a crappy weld. They both compromise the structure of the tubing. And, I don't want either on my bike. You like muffler bends, feel free to use them on yours.

Of course, if you had read anything other than just the last posting, you'd realize I already bought pre-bent tubing. And, don't plan to weld the miter joint myself anymore.

What do you mean by 'layout'? The tube fit-up or the drawing? Doesn't matter - I did both. All the pics are here in this thread. Let me know if you think I did a crappy job there, too.

No wait, don't. I don't really care what you think.

Edited by - ShelGame on 01/19/2016 06:43:24
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warren
human power expert

USA
6087 Posts

Posted - 01/19/2016 :  08:38:38  Show Profile  Visit warren's Homepage  Reply with Quote
Cleaned up some snarky posts...
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/19/2016 :  13:48:13  Show Profile  Reply with Quote
OK.

quote:
Originally posted by Jerry

I totally disagree with your second sentence. I believe you are.



quote:
Originally posted by ShelGame
I'm not dumb enough to think I can pickup a (new) torch for the first time 15 years and think I'll just get it all done on the first try.





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PUGZCAT
recumbent enthusiast

Canada
459 Posts

Posted - 01/20/2016 :  04:54:30  Show Profile  Reply with Quote
I am no great torch welding guru, but I may throw in my two cents. Off hand, I think you need a smaller torch tip. Also regular braze brazing with flux coated rods is easier and quicker and still plenty strong. Cleaning off the flux before painting is a bit of a bitch though. I like your chain ring set. Hang in there and get it done.
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warren
human power expert

USA
6087 Posts

Posted - 01/20/2016 :  05:56:08  Show Profile  Visit warren's Homepage  Reply with Quote
Yes, you are on the right path and doing great.
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/20/2016 :  05:58:13  Show Profile  Reply with Quote
Thanks guys. I'm also much more comfortable now with all of joints being brazed. Going to go look for a tracking number for my tubing from Nova...
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ShelGame
recumbent enthusiast

USA
254 Posts

Posted - 01/23/2016 :  15:12:26  Show Profile  Reply with Quote
Got the new pre-bent tube and 35mm downtube fitted in today; polished up the areas I'll be brazing. If I have time, I'll do some practice brazing tomorrow.



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warren
human power expert

USA
6087 Posts

Posted - 01/23/2016 :  19:46:16  Show Profile  Visit warren's Homepage  Reply with Quote
Nice!
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