Andrew R Stewart 

The amount of stay width that was removed is substantial, maybe about half the diameter. So I felt that a plate that adds real structural support was needed. The plate was a cut off from a shear at a local steel dealer, I visit it a couple of times a year for scrap that fits a project.

I'll continue adding shots as the process progresses. Andy

guy153

Is the plate CrMo or regular steel? I think either would be fine as it's thick enough.

Andrew R Stewart 

All I know is that it's good old "merikan steel

Really I don't know the grade but by the way it worked I suspect a mid grade, maybe 1018/1020ish. Certainly cold rolled. Cost was $2 for the 30" length and that included a dollar tip to the place's pizza fund. Andy

Cynikal 

The last place like that here closed up this year. While it was never that cheap it was a good spot for practice welding bits. I will miss it.

Andrew R Stewart 

The main triangle is nearly all brazed up. Well all the joints are "fixed in place" but my poor fillet skills will have me doing a few spot "corrections" to the fillets for looks. Here's the ST/TT joint. The TT is 1.25" and the ST is 29.8 at the top's external butt. This motivated a different blending of the different diameters then the usual. The middle/upper "U" shaped feature will remain (the rest are lumps mostly filed down by now) and I hope to have the top of the SS mimic this... Andy

guy153

Looks like a good joint to me! Is the DT also 1.25" or even fatter? I only used 28.6 TTs on both the real "hard-tail" MTB I made and the recent "soft-roader".

Doug Fattic 

Andy, I've enjoyed watching you build this frame! I thought your tire clearance method was really cleaver. Looking at your fillet I'm wondering if you had both tubes positioned so they leaning over at the same angle from vertical? Like the letter V that isn't tipping over to one side or the other? It looks like your sags were all heading in one direction maybe indicating your top tube was higher than the seat tube so the brass was running in that direction when it was melting? In other words your brass should be melting towards the miter and not away from it towards the brass edge if your tubes are most effectively positioned. Of course that means your frame can't be held in a fixture and has to be constantly moved as your fillet incircles your top tube.

I am also wondering if when you are flicking your flame off of the joint (to control your heat like an off on switch), your flame motion - as it is leaving the joint - is along the brass fillet line? Maybe your exit motion was straight towards the head tube? Just making some guesses that may not correct. If your tubes are positioned so the brass is melting towards the bottom of a V and your flame is coming on and off the top tube's miter line, than your flicking on and off doesn't have to be quite as fast to prevent a sag. And the melted brass will form a nice contoured shape.

You have got to figure out a way to make a road trip to Niles so we can swap framebuilding stories while we work on something together. Maybe you can be my assistant when I host a T tool making party later after everyone is vaccinated?

Nessism

Andy, your "poor fillet" would equal "over the moon" if I made that joint.

Enjoying your build. Keep going...

Andrew R Stewart 

Thanks guys.

Doug- I did two passes to achieve what you see. Lots of repositioning of the joints, trying to keep the aimed for area as level as I can. I had some really nice sections with globby ones adjacent. I need what I am unlikely to do, get a lot of daily practice, for many days.

Last night I started to clean up the joint I shared and the curved ends of the TT that are proud of the ST are now much more defined. As I was making the fork then the CS/rear drops I had some shapes that reached out to me and I'm trying to duplicate some of that elsewhere on this frame. Kind of odd as I view a MtB as a pretty basic tool. Sort of like a plow horse, not an athlete like a race horse (or road bike). Yet here I am doing embellishment that has no merit. But that's why we do this stuff, because we can. Andy

Doug Fattic 

Andy, you and I do a similar thing when we post on framebuilding forums and that is while I am responding to your post, I am really writing to a broader audience that might wonder how to get a better result but not exactly sure how to do it. One of the huge advantages of fillet brazing is that it can be done several times until one is satisfied with the final result.

Practicing can involve two factors. The 1st is self discovery about how to do some aspects better (like holding the rod at a better angle). The 2nd is getting more coordinated at execution. For example muscle memory allows some aspects (like the angle to hold the rod) to be automatic and doesn't require your attention to do it. A brazer's concentration can not be on what is happening at the joint and making adjustments to keep it going right.

guy153

Yes this is spot-on. And sometimes you need more of one of these than the other. When you first start out you just plain suck (or at least I did) and you don't really know where to start analyzing where you're going wrong. But with practice you get a lot better without really knowing what you're doing differently. It just gets easier and comes out better. At that point you can start to think about what you can do better in an intelligent way and actually put those things into practice.

Andrew R Stewart 

Today's progress. I filed/sanded the seat junction to about near completion and prepped the binder collar.



The above shows what i was aiming for with the TT ends being proud of the ST. This joint took less filing then the others which is why i leave it for last among the main triangle. The binder collar had a shelf in it's top but I prefer a through hole. So I started to cut away and ended up with this.



Not the usual collar I have more plans to further cut and curve the top. Tune in next week. Same bike time, same bike channel. Andy

Andrew R Stewart 

More work done. First image is of the binder collar after brazing and before soaking off flux. It cleaned up well, I'll share an after shot soon.


Next up is the pre tacking set up for the chain stays. I needed a little weight and the stays needed to be kept apart/in place. The big round thing is one of my tube caps that I place over an otherwise open ended tube to reduce the chimney affect when brazing.


Third is the same but after tacking (should have shot this before the added flux was applied...) You can see the two tacks on the stay ends undersides. There's another pair of tacks on the stay's top points.


The after brazing and soak off state.


The seat stays with enough tire clearance is now in process. This took quite some thinking and trials. I first thought about bending the stays at the tire's widest point. I also wanted a "shot in" version of the stay/tube joint but the very small amount of stay between that point and the tube's backside is very short. I did some trial bends with straight cromo stock and found the tube was flaired too much at the bend to look good, the bend radius was too large (about 6") for the fit up and i was worried about the thinner walled stays being even more problematic to bend and come out nice. So i pivoted and thought about a bridge/monostay design. That seems to hit the right nail heads so this image is the early stages of that. The top few cm of a fork blade (likely from one of the 24" ft wheeled bikes I've done) and a hand curved strip. I hope to braze this up tomorrow and have filed enough to do the miter Sunday when it will be above freezing (just so) in the garage where the mill sits. Note Alex Meade's cool fork blade clamping block. Andy

Andrew R Stewart 

Another day in the basement, another step done. The started bridge/yoke was brazed up, cleaned up, mitered to fit and brazed to the ST. What you don't see is that I added a preform (just bent and looped 3/32" rod) to the monostay before I tacked it to the yoke. This time it worked well (I have done this loading of filler inside a joint before with less then grand results) with really good wet out and internal fillet. This is the first time I have done a monostay, let alone a self made one. So far I am happy with the looks but still wonder about the long term. Andy

guy153

Looks nice! My only concern with the design is the stiffness of the yoke. People use them made like that on chainstays but the main load there is at 90 degrees to what it is here. The stiffness of a flat bar like that might be 1/5 that of a 20mm thin-wall tube. On the other hand you do also have the chainstays to resist bending and it might actually give a beneficial suspension effect!

Andrew R Stewart 

I agree with your concerns and have already thought about some reinforcement...

This frame is an experiment in many ways. I bought a small spray gun and might try painting on the garage when the weather turns warm. The chain stays clearance thing, the unicrown fork and it's drop outs, the geometry, only my third disk braked frame, first running 584 MtB wheels, first real MtB. As I am nearing completion I am beginning to think about doing what I have mocked before. Clear coating only, then build it up and see how it rides before investing time and $ in real paint. So much so different, kind of reminds me of me when I was first starting out, little history to draw from and some disregard of what others will say (yet here am I writing about this)

Today will see a stay/ring dent get done and the start of fitting the seat stays. Andy

Andrew R Stewart 

I have trial fit the crankset and only had a couple of mms of chainstay/inner ring gap. So I made more clearance. If I had really done a best job at the planning and set up I would have done this before the stays were brazed onto the shell. But I didn't. One of my stay crimpers had to be taken apart and only the two layers that sandwich the stay were used. Since the big pressure screw was no longer available for the crimping I positioned the form and snugged up the 4 draw bolts to hold all in place while I applied a 5lb irresistible force (hammer). Crimp done. Andy

Andrew R Stewart 

Finally the frame has no open loops. Still needs a lot of bits added and a few more final finishing touches but the basic structure is complete. Shot 1 is of the prebrazing set up for the seat stays. The more I use these machinist clamps the more I like them.


The after filing and sanding. The ST top and clamp is rather different then what I usually do. The ST ID did need some reaming before honing but not as much as I had thought. Andy

guy153

What do you mean "reaming before honing"? You ream the ST and then also hone it?

Andrew R Stewart 

Of course. Reaming removes a lot of material compared to honing. Much like filing VS sanding. Reaming gets the size and roundness a post wants and honing removes any remaining burrs and results in a smooth ID surface. Andy

Doug Fattic 

Andy, I've been enjoying watching the process of your MTB frame with some original ideas on the frame was well as how it is made. It is certainly nothing you could buy in a store. BTW, I encourage my frame building class students to put their frame together to ride it 1st before painting it for real just to make sure all the braze-on bits are in the right place and they haven't left one off they now wish they had. As you already stated, a clear coat over bare metal won't last long but I'm sure long enough to figure out if you need to make any changes. You might want to consider putting on just a primer instead. House of Kolor primers that come in red, blue, yellow as well as black and white are actually nice colors and might be another option for you. Because they are primary colors, they can be mixed to make almost any color.

guy153

I'm learning about new levels of perfection I'd never even heard of

Nearly every commercially made bike I've owned had issues with the seatpost slipping down unless you did the clamp up so tight you nearly broke it, especially if you greased the seatpost, which of course you should, but I ended up having to clean it off and use linseed oil instead in an attempt to achieve additional stiction.

I'm not sure they even reamed them because all my own frames are far better. Grease and moderate torque on the bolt and zero slippage, exactly as it should be.

duanedr 

What do you use for hone? I use a simple flex hone (for stem clamps as well). Looking great. I like the seat post clamp treatment.

unterhausen

I use a Flex hone from Brush Research. Is there really another option?

duanedr 

There are hone machines or those stone things they use for engine cylinder walls. There may be others that I'm not aware of - which is why I asked. I tried the stone hones but it chattered and there was very little pressure applied so the effect was minimal.