Tigging tabbed dropouts tips?

Looking for any helpful tips on this subject. I've tried tigging tab-style dropouts only once copying my old Indy Fab cross frame and it went just ok. I've brazed my other tabbed dropout builds to the stays. But i've got a frame coming up that is using 7/8" chainstays and Paragon low-mounts. Slotting the stays and filling with brass will not work in this situation. Although I saw a thread with Joe of Clockwork's method of brazing them the "Pott's" way I really want to dial in the "Firefly" or "Indy Fab" (and many others) way using TIG.
What's your process and how is this done right and well?

Thanks,
Whit

Here's my first attempt to show ...Attachment 68201

Whit,

I'm not sure what exact questions you have as the process is fairly straight forward, but I'll share a few thoughts...

Mark's dropouts are notoriously unsuited for capped/scallopped finishes when using large diameter stays. The height of the dropout tab needs to fill the diameter of the tube for a strong joint. Instead, you are forced to fill the area above and below the tab as the stay wraps around it. One of the reasons the examples you have used make their own dropouts.

The tube should be notched to accept the dropout tab predujiced to the inside, so that the stay meets the tab as flat as possible, minimizing the amount of fill for the remaining curved section of the tube.

Get some flat stock 4130 of at least .045" to create your plates. Leave them a couple thousandths proud so you may use the extra to help fill and roll over the joint.

If I'm doing scallopped ends, I will set the radius of the scallop with the hole saw and then cut the curved plate out of the same size tube using a cutter one size up, then snip off the flat transistion.

I tack mine with the stays pointing toward the ceiling and argon flowing down into the joint, this insures that this critical weld is as contaminant free both inside and out as possible.

Leave the weld unfiled unless you used a heavy plate and have full penetration...filed joints with poor penetration will fail quickly in the area due to torsional load.

Here's a pic of a Ti frame with flat capped transistions...

Attachment 68348

Check out Drew's stuff as well, as he had his own dropout made to deal with many of the issues we just discussed and has the process dialed for his aesthetic.

rody

IMO this is one of the hardest things to do with bicycle fabrication and have it look clean. I do not like the look of a proud weld on the actual tab of the drop out so it needs to be done right to allow proper penetration and filler and have a smooth transition. It is very difficult to weld .250" plate to .050" sheet to .028"-.039" stay material all in the same spot. Requires good welding skills and a good process. Here is a 1" chainstay (.028") showing a clean transition into my drop out which was designed to allow the use of a 1" stay (just welded today). Paragon's stock drop outs are designed for bullets IMO and there is not enough material there to make a strong and flowing connection.

https://farm4.staticflickr.com/3902/...cd6160b1_o.jpg

Rody,
This was exactly what I was hoping for. I was wondering how you did your Ti 29+ seen on your blog with the low-mounts so cleanly. I was having trouble making it all fit on the low mounts, so knowing those dropouts aren't ideal for this setup makes a lot of sense and will make me consider other dropout options (next time...). You seem to do pretty well with Paragon's dropouts and this method on your bikes!

The welding in one plane was the headscratcher at first. Maybe it is the small real estate on the dropout but it seemed less than ideal in rigidity and strength but i know it's been well tested. I was wondering if you or others somehow welded the inside of the tab to the tube or just around the tube and cap.

For process, I first tacked the stays to the dropouts in the fixture, then used filler to weld on the caps, then welded the stays across each side of the dropouts. It seemed pretty easy to 'cook' the joint, partly due to imperfect fitup because the narrow tabs and large diameter stays. What do you recommend for process, and do you just fuse the cap to the coped stay or weld it normally with filler?

Lastly, I 'popped' the caps out of the same diameter tube as the coped stay for the end caps and filed down to make fit. Is there a faster way you use for the end caps?

Thank you for the reply!
Whit

Drew,
I'm glad you consider this difficult to do right, you have perfect examples of what I strive for.
I've only been able to make "proud" welds on the tab/cap interface (i'd call them more of the "humble" sort though...), like what you see in my first example and it's because of the thin-walled stay being welded to the thick tab.
On steel would you do a two-pass technique like on Ti? I know you need a lot of heat and to move fast, but is there any way you minimize the chances of cooking the joint with a given process? Hoping i'm not asking too much, just looking for tips.

Thanks,
Whit

That drop out is all done in one pass even with titanium. Too much risk of contamination to attempt to fusion weld it first. Only the main welds are fusion pass. Bridge and drop outs are done in standard single pass. The process requires a good back shield to capture the argon coming out of your torch and hold it in the area you are welding. Fit up needs to be good as well since you are running gas from the inside which will escape and make welding harder if there are gaps. Flat caps are better for the cap to drop out transition gives you a better valley to put your weld. Unless you are committed to this style of attachment it is not really worth the effort for one or two bikes a year (unless time is not a concern). You will need to send stuff to the recycling bin of you want to get the process down.

Attachment 68852Attachment 68853
We have been finishing some tab style dropouts this way for a couple bikes. I think with a little more finish work it could be done nicely on a one off frame. We notch it out with a belt sander and then tap it over the edge of a table with a hammer. This provides lots of weld surface and not putting all the stress on very end of the tube. If the stay has a seam of internal scaring it can crack when being formed, kind of a bummer if you only have one set.