I thought I was done building bike frames for this lifetime but my son came home last weekend with his new Specialized Stumpjumper comp. I really like the ride of the 700c mtb wheels especially on the loose sandy trails I'm often riding these days. I never thought the difference would be that great over 26". I can do without the suspension fork though.

After I did a quick sketch and some searching ,it looks like I could use OS road lugs without too much cutting, beating and bending. Darrell McClulloch's sloping TT lug set with a Nova BB and their chain-stays looks like it should work pretty well. I could make the 400mm axle-to-crown fork using Pacenti's beautiful MTB fork crown (is he still in business?)

Anyone here built one?

"Pacenti's beautiful MTB fork crown (is he still in business?)"

Yes, I ordered a few things yesterday. https://www.bikelugs.com/store/index....l&intItemID=46

BTW he has the crown on sale(along with other things).

Brian

Thanks Brian! I must have had an old link, That is good price on the crown, I was thinking I might have to disassemble a 26'' fork I made using his crown several years ago.

I've built a couple. If you want to use off the shelf lug sets and bb shells, you have to be willing to compromise things like tire clearance, bb drop, and chainstay length...none of those will be optimal.

It is certainly going to take some whittling on the downtube and chainstay ports to get it close to where it needs to be. Tire clearance I can manage to get about 7 cm between the chainstays using a single bend if I have a 46cm chainstay length. I'm trying to get a sketch of the s-bend stays from Nova, My only previous experience with s-bend stays was 28 years ago (Reynolds IIRC) They were designed to come square off the bottom bracket not at an angle like a single bend stay.

I looked through your Flickr Album this morning, nice work!

Do the main tube sizes of the nova MTB BB suite your project? That is thier only BB with 10° chainstay ports, the other BB they have are all road 7° ports. YOu might look at using a Sachs BB, I think they are cast with more tire clearance in mind than typical road BB.

You would also be much less constrained by pre-cast angles, get more tire clearance and suit whatever tubes you want if you used a lugless / fillet brazed BB shell, could still be combine with lugs elsewhere on the main triangle.

Raleigh built plenty of lugged "28ers" back in the day. I wonder if you scrapped the fenders and did the appropriate mods, one of the Roadster frames would take 700C wheels with 29er tires...

The Nova( Everest) BB would be less work with the file and dremel but I would like to use the s bend chainstays (I'm told they will work fine with a lugged BB) Changing angles in the CS ports is pretty easy I have done several times.

As for Sachs, I built one frame 7 years ago using his lugs, crown and BB. Best quality I had ever worked with. Then he stopped selling to us hobbyists several years ago.

I have avoided filleting bottom brackets, I'm going to continue to do so

It probably would, but if I was cheaping out , I would just order a $179 cheap-a-nese frame from Nashbar and ride it.

But after reading your post early this morning I started thinking. I have some 2.5" wide Berthoud fenders and a box of old english 3 speed Raleigh bike bits. I could do a 29er with big-a$$ 2.5 tires, a Raleigh paint scheme on the frame and fenders along with some of the old Raleigh parts like the tail lights, chain guard and Brooks B66 sprung saddle . Instead of derailleurs I could use a Shimano Nexus 8 speed hub.

I doodled on paper over the weekend and then while looking for something online I came across this simple bike CAD program that even a computer simpleton like me can figure out, Rattle-Cad. So here is what I can up with.



All of the cockpit dimensions coincide with my two current 26" MTBs. The only real difference is the top tube is 2 cm longer(2 cm shorter stem) so my size 13 1/2 feet clear the front wheel.

Most of the work will concern the 63 deg downtube . I have made 3 degree angle changes in lugs before so I used that as a bench mark. I lengthened the rigid fork to 425mm, lowered the bottom bracket height(7cm drop) and gave up 1/2 degree head angle ( I wanted 70). The bottom bracket angle spread is 125 deg, Nova has a long point BB with a 126mm spread that will work with minimal work. The lugs will be 6 deg Llewellyn's.

The 485mm chainstays are the same as my 26" MTB offroad tour-er which handles far better on loose trails than my standard MTB which is identical except for having shorter 435 mm chainstays.

I am staying with 31.7/28.6/28.6 tubing, I was thinking about going bigger diameter but decided to stay with what I know is working for me.

I was browsing through Ceeway's catalog and found they have a set of 29'er lugs and bottom bracket shell ! Quoted $71 with shipping to NY