unterhausen

Aircraft Spruce is selling the best 4130 right now. All the other guys are getting Chinese stuff that is often pitted, I saw a discussion of plating not working well on some racks because the tubing was pitted.

tuz

Yes I get my cromo and stainless from Aircraft Spruce in Brantford. I did get a few tubes showing some pitting but for the most part it's great stuff.

BTW regarding Allstate 11. The LWS has a little booklet saying it has a working range from 650C to 950C, with a remelt at 950C. That it works well with 2-4 thou radial clearance... Sounds pretty cool!

veryredbike

Just got 3 36" chromo tubes in the mail, 5/16 .035. They actually ended up throwing in about 10" of it for free. Not bad!

I've also got a tube of 1/4 and a cheap bender on the way.

I've got some sketches together for what it'll look like. I think it's going to be good, but I need to figure out where I use the heavy duty stuff and where I use the light stuff.

Which areas would you say are under the most strain? My thought is that I can use the heavier stuff for three "covered wagon" style arches and use the lighter stuff for the crossbar that the panier attaches to, since it's supported at three points. Thoughts? Should I use a heavier piece for the crosspiece?

PaPa

The racks that i've broke is nearly always at the attachment mounts near the drop outs. This is typically where the greatest bending loads are (from the loaded rake swaying side-to-side).

veryredbike

Hmmm... that mirrors what I've seen at the shop. Since I've got tubing that will nest, maybe I'll add a bit of 1/4 tubing inside the 5/16 right around the dropout area... taper it so that it doesn't create a stress riser at the end...

If I'm brazing a rod right along the side of the vertical struts of the rack... does it make sense to miter the side of it a bit to increase the contact area, or am I better off keeping both whole and just building up a nice big fillet?

Thanks,
Jim

unterhausen

in general, the more contact area the better for a brazed joint. However, in this case I'd just run them side by side and call it good

triathloner

If I'm reading aircraft spruce's website right, you paid 50 bucks plus shipping? I think we need a group buy somewhere. Those prices are spendy, though I can't find it cheaper anywhere. I want to make a bunch of racks, and can't afford that.

PaPa

Aircraft Spruce has typically been cheapest for me, but You might wanna check these others too. Especially if you're within travel distance.

https://www.airpartsinc.com/ (KC,KS)
Dillsburg Aeroplane Works (PA)
https://www.wicks.com/ (IL)

MassiveD

Making racks is spendy, while it doesn't really help, I try to think of my racks in comparison to what a custom rack would cost. You can spend 300 and more. So when all the bills for gas, silver, tubing, fixturing, and powdercoating or chrome build up it isn't going to make much sense if I compare it to a Chinese made Blackburn copy.

unterhausen

Dillsburg is Wicks, unfortunately. Dillsburg would always give you a better price if you were willing to buy a full length, which is approximately 20'

But as MassiveD notes, there really isn't any way to escape the expense. Although the stainless from McMaster is pretty cheap

veryredbike

Ok, I started in on it!

https://curmudgeonbicycles.blogspot.c...ck-part-1.html

I've got a thread going with progress on my first bike build, and I'll keep posting there as I continue with it, but I figured for the very beginning I might as well throw it up here, since this thread has been so active and informative.

veryredbike

Quick question. I'm attaching a metal barrel to a 1/4 tube. I'll also be brazing a washer to the side of the barrel. My thought is that it'd make sense to use two fillers so that I don't mess one thing up when I do the other.

LFB for the tube attachment, system 48 silver for the washer? Does that make sense? Just out of curiosity, would 48% silver be sufficient for both if I wanted to do it that way? It's going to be the rack's strut to the seat cluster area. I'm only using one, so the joints need to be fairly burly.

I'm making a lot of progress, but I still don't have a great idea of how strong a joint is going to be based on materials.

unterhausen

not sure why you want the washer. I would probably do both with LFB. Generally, you have to work pretty hard to re-flow lfb by mistake, although I did manage to do it recently

veryredbike

Sounds good! The barrel is big enough for the head of the bolt to go through. The bolt tightens to the washer and the barrel shrouds it. I think it'll look good.

unterhausen

I thought you might be capping the tube, but you said something about the side and I was confused

Andrew R Stewart 

VRB- agreed with Eric on the unlikihood of reflowing LFB when two joints are in close proximity. Still i do do the two temp filler thing on some of my joints to be sure. Maybe tacking the first and flowing it and the second in the next step? Andy

veryredbike

Ah, woops, yeah. Meant the end.

Thanks guys, I'll take your advice and do it with LFB.

JimBeans83

@C - has this ( 8989K461 ) been strong enough for the side struts for the rack ? It looks like the same that's also in coil form , which is incredibly ductile.

https://www.mcmaster.com/#catalog/118/145/=hsscyz