Some ideas for a custom build
 

So I have a crafty friend who has built maybe 5-7 lugged frames over the past few years. He currently resides in Boston and hangs out with some pro frame builders in their shop and uses their tools. I have chatted with him a bit and he has offered to build me a frame at about cost. In addition, I bought a tube set enough to build a frame for about $40, so I thought that this might be a great opportunity to have something unique that is more tailored to me. Looking for a lugged sport touring type bike.

I am going to a physical therapist that has fit me to my litespeed in the past. He has one of those Calfee custom sizers. This will be nice because it will take some of the guesswork out for him since he doesn't have any significant amount of experience in fitting.

So here are some questions:

1) I might ask him to try to do an extended seat tube like this: http://cdn3.media.cyclingnews.future...atmast_600.jpg
With this kind of design, do you still need to have a seat post penetrate a couple of inches past the the top tube? Is this possible to do this with a lug? Would you trust an amateur to take on a job like this?

2) My fitter in the past told me that since I have short legs and a longer torso, I would benefit from a slightly sloping TT. I am 5'4" and don't usually have a plethora of space between the TT and my junk when standing flat footed. I've never had problems, but it'd be nice :) Are lugsets that accommodate sloping TTs readily available? I'd want a very slight slope so it can still give a little bit more of a traditional look.

3) I've always wondered about this question, but was afraid that I'd get flamed for it. Oh well, it's time to ask. If an amateur builder and a pro builder puts together a frameset that only differs in things like clean brazing/welds, but tubeset/geometry is the same, would you notice any differences in ride quality?

Of course, I can ask my friend these questions, but I'd like to sound a bit more informed before I fire away. Any insight would be greatly appreciated!

1- I'm not sure i'd want such an extention of the ST above the TT. There is a reason that seat posts have a min insertion mark. It's to make sure the post extends below the junction of the TT and ST. Have your friend do a test build first with the extended ST and test to destruction, then decide if it's going to hold up for you. This is one of the answers to #3. The pro has done this trial and rejects or is good with designs before you ride the finished product.

2- Sloping TTs are common these days. Some lug sets exist for this design. Lugs can be tweaked a little bit for further angle changing. Have your friend help you here. he is the one building the bike and has the motivation to choose parts that both work as a final product as well work for his skill set. Another reason to trust the pro more, he has the experience in knowing which parts work for the design.

3- In theory if the design is the same, the torch control and brazing the same, the mitering the same, the paint the same (go on here with other building aspects) then the finished product is the same. but the finished bike is more the this to some customers. The name on the frame means a lot to some. The ability to fall back on a warranty has a value. Whether there's insurance (or not) could come into play if something goes wrong and some one gets hurt (and this might not be the rider or decided by the rider).

Last point i'll make is that I would be very hesitant to build a bike that the customer was providing the parts for and trying to control the design strongly. As the builder I have a stake in the finished bike meeting many needs, the customer might not be taking all of them into consideration. As a builder my reputation might be worth more then the profit. (Oh yes, you mentioned that there would be no profit). I have been is your friends position and ended up giving back my customer/friend's deposit to keep the friendship. Andy.

1: A normal seat tube is quite thin at the top because it is supported by the top tube and the stays near the load point so there is little bending moment supported by the tube itself. If you move the load point away from the tube junction, the tube needs to be reinforced to carry the extra bending moment which increases as the square of the distance, so doubling the tube extension quadruples the bending moment. Whoever builds the frame needs to be able to calculate the extra tubing thickness required to support this extra bending moment.

A thought experiment: place the frame with the seat tube horizontal and the head tube up, supported at the dropouts and the seat stay junction. Now jump on the end of the seat tube extension and see what happens.

If you think the frame will never see that much load when ridden, think again.

2. Darren McCulloch (Llewellyn Bikes in QLD, Oz) designs very nice lugs for sloped geometries, available direct and from Ceeway in the UK and Nova in the USA.

3. In theory probably not, but in practice probably yes. A professional will make your frame his way, which will probably be better than your frame your way.

Thanks guys. Apparently, I'm totally looking at this the wrong way. I'll let him lead :)

I just thought it'd be fun to try out something new, but I guess I don't want to have half a seat tube jammed in my ass. I just saw that extension on a Hampsten and a few others frames and thought it looked awesome. I didn't know if the seatpost penetrated far enough. There was a MTB frame, however, with the extended tube and a very stubby seatpost.

Chime in from small wheel world.. Bike Friday uses a seat post mast,
of extended length,
but the tube OD is oversize, straight gage, with a machined Al shim at the top
to go down to fit the seat post standard size of 27.2.



BiFri folds.. Bene: the low step over. I swing my leg
in front of the saddle, in dismounts.


I note brace tubes and gussets added in some situations,
like X frame MTB's..

A seattube extension isn't necessarily a bad idea. It's done a fair bit around the industry so it can't be all bad. I don't know how others deal with it around the seat cluster, or if they use a conventional seat post extending below this junction, but the ISPs out there obviously don't have a seat post as such. Don't tell this guy it can't or shouldn't be done. http://www.englishcycles.com/ Note that his stays are attached lower that top tube junction as well. Cool stuff!

That said- I do it too. I do it a little differently than the ISP guys. I use a conventional seat post with most of it's length removed (you only need insertion below the clamp.) The reasons I do it are...

One- I don't like the appearance of a conventional seat post sticking up above the clamp. Two- It saves weight. Three- there is always distortion in the tubes at the seat cluster, so by extending the seat tube there is no need to ream for seatpost fit, which I feel weakens that joint on an already thin seat tube.

The downside is that there is no height adjustment so you better get the fit right. One upside? No one asks to ride my bikes because they probably won't fit them unless thay are the same size as me.

I've also done it on two lugged frames but the appearance (improvement) aspect just doesn't fit lugs.

Just because I do it doesn't make it right. I don't do any fatigue testing except by actual seat of the pants mileage. So far so good, and in the case it isn't you'll get plenty of warning before the seat tube pokes you in the butt. I don't build for others so I needn't worry about the problem of either durability or liability. Like you, I am also short, so also light weight.

For some reason I can't insert a pic, but here's the link to the latest bike (only #10)

First is completed frame before paint. Before painting I thrashed this bike for roughly 800 miles.

http://imageshack.us/a/img593/1504/readyforpaint.jpg

Second is the same frame just painted. Looks sooo much better than the rust. Ride weight- 16# 3oz.

http://imageshack.us/a/img832/2655/newbiker.jpg

with that shaped tube it's not really representative of the potential failure you would see with a round tube ISP.

I always wondered what Rob English's failure rate was like. I see production bikes that were not made to be weight weenie bikes fail all the time in the top tube/seat stay area. And I hear custom builders talking about failures in the places where he has no reinforcements. Admittedly, a lot of those are on mountain bikes.

I have thought about doing an ISP, but they generally weigh more and are more expensive than a standard seatpost arrangement. I would never do a lugless bike without a reinforcement at the top tube/seat stay junction, but even that might not be enough for an ISP.

Andrew; +2 on it. I am of the opinion that the minimum insertion line on seat posts is just a "boiled down to idiot proof" level way for the manufacturers to suggest how the rank amateur can use their product without completely "&*%ing" it up. Probably also is an attempt to do a littel CYA for liability purposes. Eitherway, the extended seat tube shown breaks most assumptions... If I was asked to build that bike frame, I would swap out the normal seat tube for a fairly heavy straight gauge tube of the right diameter. Might even add an additional next size smaller tube inside it as a sleeve going down about 12 inches past the top tube intersection and just sweat it with silver after the main tubes are done... Worse case I might have to find or make him a seat-post to fit, but at least he wouldn't wreck the family jewels on a broken stub of CroMo...

Ksisler- Agreed that an extender seat tube (EST?) need heaver, stronger, stiffer tuing. I think this is why Eric says they are heaver (weigh more). I, too, have seen a few broken off ST tops from too much post extention.

reddog3- I'd like to see aclose up of your rear canti bosses. I've done a few canti mounts which needed more contact to the seat stays (IMO) and sleeved the canti boss base with larger tubing. Yours look like this might be the case too. Interestingly this is the same issue as ESTs but with brakes. Andy.

Andy- Most folks don't pick up on my strange (brake fetish.) I like the feel of linear pull (v-brakes) when coupled with canti or road, short pull levers. I've used this combo a lot on my personal bikes after some experimentation to figure out what works for me. You can't put V-brakes on a road/race bike?

I'd be more than happy to send you a closeup, but text will probably explain it better.

On this particular frame the "boss" to stay is a chunk of .8x14mm (leftover seatstay cutoff). It's notched to fit the stay. I've never felt than attaching that "hunk" of canti boss was the best idea, so this was my solution.

What I did (once the spacing was determined)(the tubes were notched and attached determining the spacing) was take an available boss and machine it to fit the tube. Every effort was made to remove as much weight as possible- within reason of course.

The extension of the "boss" below the stay has a purpose. I made an aluminum bung and epoxied it into to the the canti boss tube. If I noticed deflection in the stay with brake application I was going to fashion a brace (similar to a fork brace) and attach it with a center drilled aluminum bolt.

No need for the brace. These (thin walled stays) have nothing in comparison to the deflection that my factory built Alu frame has.

Thanks- Donn L

http://bikeforums.net/attachment.php...hmentid=282914In a further attempt to hijack this thread- Donn L- here's a shot of what I was talking about re canti bosses being beefed up. Andy.