mikeread

My Audax runs 32 spoke Ambrosio rims - very similar to open pro's I then run 25 or 28mm tyres at 80 psi front and 90 back. Frame is Reynolds 631 OS (28.6 28.6 31.7 .8.5.8)

Regarding front end comfort, the road shocks will travel up through the tyres, wheels, fork and bars to your hands. I cannot see how the frame will make much difference to this except perhaps the head tube supporting and reducing flex in the steerer tube.

I suspect that rear end comfort is mainly down to tyres, wheels, seatpost and saddle with the frame contributing - but maybe not much.

Recent experiences with an alloy frame - which I sold as it was so harsh, may have been mostly because of the stiff, over size bars and cheap alloy seatpost. I suspect the straight bladed, monster size, disc forks didn't help either.

So the frame I am building - (Double OS) should be comfortable to ride as long as I select bars and seatpost carefully.

So I am going to keep a look out for some NOS Deda 215 26mm bars - and a girvin flex stem

I would like to make my own tapered titanium seatpost but suspect this is beyond my capabilities.

Nessism

The front end doesn't flex a whole lot in the vertical plane, but there is some. You mentioned going with Columbus in other thread about poor dimensional (thickness) control by Reynolds.
What exact tubes are you going to use? And what fork? The fork has a significant effect on ride quality.

Regarding rear end flex in the vertical plane, I think that's much less than the front. And I don't think the seat post flexes much either unless you have a massive amount of post exposed.

mikeread

The tubes I bought in the end were a mixture of Columbus Niobium and Columbus Zona .8/5/8 and .8/.6 for the seat tube Double OS. Fork is Columbus Minimal 1 1/8. I am over 6 foot and 170 lbs

I am building with a sloping top tube for a long exposed seat post length - I am sure this has a bit of flex.

I have had a few days in the workshop over Christmas and my jig and tube clamps are finished. The clamps took longer to make than the jig!! and I learned a lot about using a DTI and a 4 jaw chuck. I told my 11 year old daughter I was making tinsel :-)

Tomorrow I will make a couple of drum sanders for cutting accurate miters. Then I just need my lugs (on back order) to get started - and an Oxy Propane set and ........................

Road Fan

Mike, the road shock does travel up the steer tube, but it also has force components perpendicular to the steer tube - the wheel can be knocked back and up or even forward and up. Then the fork flexes and rings due to the impact. The inital force is a sharp pulse, and the higher frequency ringing components of motion should be mainly transverse at least due to fork ringing. Some of this complex of energy is carried axially and transversely into the frame due to continuous headset bearing contact, and we can expect some new ringing to start at the frame/rider/loading resonant frequency, with damping so it tends to die out the high frequencies. Some goes into lifting the head tube which helps to lift your handlebars and the saddle. This all is much too complex to fully deal with in words. Perhaps they should flex as a result - both Nessism and I appreciate the comfort of an O/S thinwall frame like ELOS, and it has to have energy input from the fork. 853, also oversize and thinwall, should have similar characteristics.

It's also a physical reality that it's practically challenging to go much thinner than 0.4 mm without really exotic alloys like 953, and a double oversize has a rather higher 2nd moment than single oversize like ELOS so it is stiffer as long as it doesn't beer can. How much performance you get out of 2nd OS versus OS is certainly a complex question, and debatable. Damping can be provided by the tires, the tape, the saddle, and the rider, ignoring any racks or luggage. We all know softer tires give a ride that feels smoother, and that well-broken-in leather can feel softer to ride than say a Toupe without gel. The frame can reduce vibration but not convert the energy to heat, so it's technically not damping though it may improve the way the bike feels.

Any case, I think the frame has a lot to do with shock absorption at the handlebars. At least I think there are good reasons not to discount it.

However, I see you have by now bought tubes and are marching down your road. I wish I knew how to make a frame.

unterhausen

there is a slow motion video on youtube of someone doing a bunny hop on a road bike. The fork deflection is pretty amazing. It really recalibrated my notion of how much a fork steerer contributes to the deflection of a fork. It's a lot.

mikeread

Thanks Road Fan, what you say makes sense.

As you say, I am committed now so I guess I will find out - for better or worse.

If I don't like it I will learn, move on and make another :-)

Unterhausen - Just flicked through a few bunny hop vids, I couldnt see a lot, they were all BMX style with short - probably solid forks - I gave up looking when I actually got to real hopping Bunnies.

I don't doubt you though, I can see my fork flexing when I am riding.

Andrew R Stewart 

I learned about steerer stiffness with making myself three loaded touring bikes with 1" steerers, then one with a 1 1/8" steerer. This last one is far more confident to ride. I doubt I'll ever go back to 1" for a stressed bike again. Andy (which is almost too bad as I have a lot of 1" fork stuff on my shelves).

unterhausen

against my better judgement, I have plans to make a 1" disc fork. Hey, you can buy one (from Crust).

Andrew R Stewart 

It all depends on how much you lay into the front brake, from what I've heard Andy

unterhausen

if the brakes don't stop you, something will (stolen from an AT&T ad)

Andrew R Stewart 

"If the thunder don't get you then the lightning will" is how I heard it (Garcia "the Wheel") Andy

mikeread

Happy new year to you all.

Positioning braze-ons ?

Is it OK to put rear brake cable bosses on the tapered section of the butt or must they be on the thick,end section?

Are there any recommended dimensions for where you place these items to get the best cable run? Anything I should look out for?

I am using Llewellyn limpets which have quite a large contact area. Also is it worth rounding off the corners on these cable stops as they are quite sharp?

I have been left at home alone over the holiday and its amazing how much you can get done with no interruptions or distractions! I will post some pics of progress when the weather clears up. There isnt enough room - or light in my workshop to take a photo and I dont want to take my shiny tubes out in the rain!

Thanks

Mike

Nessism

It should be fine to put the cable stops on the taper section. Those limpets are specifically designed to provide extra surface area to assure the tube won't tear in extreme usage. And don't think there is any need to modify them other than I suggest smoothing out the casting before install because they are a pain to smooth after application. I also suggest putting a chunk of silver in the cutout on the inside; this will assure silver gets underneath.

Andrew R Stewart 

Mike- I like to locate cable casing stops a bit further from the tube ends then most do. Yes this means attaching on the taper or even the thin section. Why? Because I am a shop mechanic and grow tired of too short casing loops that contribute to friction and add a spring like force to the calipers or bars. But I ride smaller frames and the casing loops are already shorter then most. I take some care to cable path and the ability to service cables in the future, so all my stops are slotted for cable removal. Andy

mikeread

Progress so far:

The jig is a simplified Arctos type and was very easy to build, the tube clamps took longer !! I might improve the rear axle holder at some point and the brackets for the cones need to be guided better as there is some side to side play, but it is OK as is for the first frame.

The drum sanders were very effective and I dont think I could get the mitres any better. The sanders don't remove material very fast so I had to do some hacksaw cuts first. The second mitre on the top tube took some time as I had to go little at a time. I have a 3HP belt sander in my workshop which would cut mitres in seconds but building a jig to hold the tubes would have been a big job - one day.

I am all worked up now as my lugs are on back order.

WheelNut2

You can always try to build up a little bit of a fillet around the edge of the cable stop to provide a smoother stress transition if your concerned about stress risers on your cable stops. Brazing material with a slightly lower silver content will build a bit of a fillet. You could experiment with some 30% silver. The problem is of course that brazing cable stops without creating hot spots using 56% silver is hard enough as it is. Trying to build a bit of fillet will be more difficult, but not impossible if you practice a bit on some sacrificial parts.

mikeread

I completed my first practice lug today, Photos below are immediately after brazing, I have overfilled the shore line in a couple of places but penetration looks OK, I will quarter it to check when I get back in the workshop.

I dont think I overheated the tubes, It did glow a dull red at times but I believe this is OK? Your expert opinions would be much appreciated.

Thanks

Mike

unterhausen

I am pretty sure that spot on the tube got a little too hot, nothing too severe though.

The important spot is inside the lug ears, do you see filler in there? without cutting it apart, that is the point where you can see if you got penetration

Andrew R Stewart 

As a practice piece that the binder ears are hollow (this is besides the flow Eric referenced, IMO) doesn't mater. But for a real frame leaving the ears hollow is asking for future problems. Hollow ears tend to distort/crush in with binder pressure. Andy

Nessism

For what it's worth here is a photo stolen from Richard Sach's flickr site showing how much flux he uses. Maybe excessive but with this much flux you don't need to worry not having enough and leaving the joint open to burning.
Oh, and for what it's worth, I bought some Gasflux Type U for silver and didn't like it because it just runs off the joint when heated (leading to the possibility for charring the joint.) I rejuvenated some old Harris Stay-Silv that had dried out by adding water and was much happier with it.



DSC06312 by e-RICHIE, on Flickr

unterhausen

I always say you can't put on too much flux, particularly if there are photographers around.

Mike's piece definitely looks worse because he didn't clean it. I would like to see it cleaned.

There is puddling in a couple of spots. I would move that around. Usually you can pull that inside the lug. Or it could be moved inside the ears. That's one reason I leave the seat tube long, if I really get out of control with filler, I can pull it onto the excess tube. Filing is just horrible work, try not to do any.

Andrew R Stewart 

I get my flame's inner cone right up against the still moist flux and dry it out ASAP before more general heating up. Andy

mikeread

Unterhausen - by hot spot, do you mean the red/black patch? Is there anything in particular that indicates overheating? I will clean it up and section it today if I get time.

I am not worried about the binder bolt and was a bit mean with the flux, I dont want to use it all up on practice pieces :-)

Thanks

Mike

unterhausen

is flux really expensive for you?

Red means you oxidized it. Black is carbon precipitating out, and is normal. Particularly if you didn't use much flux. I wouldn't really worry about overheating a lug, except it means you might stop penetration. The only reason I mentioned the lug ears is because there should be a fillet inside there if you did a good job of brazing. It's a really good measure of how well you did. Obviously you don't care about the strength of those ears. I can't tell if there is filler visible there or not.

I think you should clean it, flux it back up and try to clean up the shorelines.

mikeread

Regarding the flux - I am just a bit mean :-)

Good idea to clean up the shore lines, I will have a go before chopping it up, I have washed the flux off now and it has a bit of rust in places so not sure how well the silver will flow.