Retrobike Forum Index

It is currently Fri Dec 09, 2016 3:10 am

* Login   * Register * Search  * FAQ



Post new topic Reply to topic  [ 4 posts ] 
Author Message
 Post subject: Conifer Customisation
PostPosted: Thu Oct 17, 2013 10:51 pm 
Retro Guru
User avatar

Joined: Mon Sep 24, 2012 9:10 pm
Posts: 669
Gotta be spam, right?.... Wrong. Although this is probably even more of a minority interest than that. Trees are flavour of the month- over on 'readers road bikes' you've got pauln cutting bike frames out of trees and making them a few sizes smaller, and Gastheerg has a rifled hardwood peg inside his white Gios fork steerer. wtf is this thread about? An introduction:

Those of us who came of age in the '70s or beyond got used to the idea of parallel frames- by default 73/73 seat-tube/head-tube. Before that, it seems that frames were more often slacker in the seat-tube than the head-tube. This would have helped to accomodate the ubiquitous Brooks saddle, with it's built-in reluctance to being positioned far back on the seatpost.

Having spent the late 70s perched on a leather/foam covered plastic saddle typical of the time, I never quite twigged :| that I was oftentimes sitting on the rear rim of the saddle, even though it was as far back as I could get it. It felt like not much was keeping me from falling off the back of the saddle except the insides of my thighs. When I started using a Brooks, this became obvious, because I found myself always sitting on rivets, and there's not enough lard on my posterior to ignore that. What's the point in having a comfortable saddle if you barely get to use the comfortable bit?

The relative position of saddle to bottom bracket is primary to getting comfortable on a bike. You'd think this was only a problem for tall riders, but I'm not that tall... about 5' 10". A few threads on the CTC forum explore this problem, with requests for 'layback' seatposts and complaints about framebuilding fashions. It seems that riders with shorter thighs and longer shanks can get comfortable, with an in-line seatpost if necessary, but, short of a custom frame, or an older one with relaxed seat-tube angle, those of us long in the thigh and short in the shank are left short-changed. Doctoring the rail-clamp on my existing seatpost and getting the Brooks as far back as it will go puts the nose of the saddle about three inches behind the bottom-bracket on my 73deg. parallel frame. That's likely an extreme position already, and possibly a saddle-rail stressor too, but even so, I think I woud be happier with four inches. Some of us are just built that way...

So... I explored the layback seatpost market, such as it is: A beautiful (and very expensive) chromoly Nitto, Velo Orange Gran Cru, Zoom, and many pretenders with barely more (if any) layback than standard. I'm a stingy bastard. No way am I spending over £100 on a seatpost, beautiful as it is... or even a third of £100... so, I was left casting about for a cheapskate solution.......

Luckily I was able to find a new plain steel 27.2 seatpost. What I intended to do was bend it. That requires a fair bit of leverage. Which required a fair bit of preparation. About three days of preparation for about 10 seconds of actual seatpost bending. Rooting :( around in the shed I found a seven and a half foot long piece of 3" square softwood, and some scraps of mild steel plate about 1/8th of an inch thick. I spent a fair bit of time getting a 27.2mm hole in two pieces of that mild steel. One of the steel scraps had a short piece spot-welded on at a right-angle. I wanted to wrap that piece around the end of the piece of softwood, so I spent another fair bit of time bending another right-angle into the steel in the vice, mainly using a big adjustable spanner as a lever. A bit of hacksawing in the 'angle' and I was able to hammer it down into a right-angle. I got that plate on the end of the piece of softwood with a nice tight fit, and then used auger bits and a hand-brace to bore into the end-grain (through the 27.2mm hole in the steel) of the softwood piece- first a one inch auger bit, then, a bit deeper with 3/4 inch. When I had a deep enough hole to accomodate the top three inches of the seatpost, I hammered the seatpost into the hole. Again a nice tight fit was what I was aiming for. When I had done, I couldn't get the seatpost out by hand, and, laying the 7 1/2 ft. length on the ground, I could stand on the seatpin, lifting the other end of the 7 1/2 ft. That was my test. Tight enough. Here is the result in the photo.. along with a hardwood peg which is an interference fit inside the bottom 5" of the seatpin. I had to hacksaw off the bottom few mm. of the seatpost, with it's inside 'lip' so that I would be able to get that peg in. As you can see, years of dedicated practice have enabled me to bore dead-straight into end-grain, with the help of a few stiff drinks to calm my nerves...
Image

So.. that was my lever sorted. Now I needed a secure anchor for my levering, which is where the conifer comes in. It needn't be a conifer- it just happened to be one- one that was already dead I might add. I wouldn't do this to a living tree.
I cut a shallow mortise not far from the base of the tree, and secured the other mild-steel plate- with it's 27.2mm hole- in the mortise with two coach-screws.
I now needed to bore a seatpin sized hole in the tree at least as deep as the seatpin would be in the frame seat-tube. About 5". You know I'm a stingy bastard don't you? did somebody mention that? If I had any sense I might have got myself a 27mm auger-bit to bore that hole- instead I saved money and used a 25mm. bit- which I already had- and then spent ages enlarging the hole from 25mm to 27.2mm by various inefficient methods. When I was satisfied that I would be able to get the bottom 5" of the seatpost into (and out of) the hole, I made a hardwood form to guide the bend, cut another shallow mortise in the tree for it, and secured it with another coach-screw. Here is the result of my efforts...
Image

Now I was almost ready to bend. All that remained to be done was to fill the hopefully soon-to-be-bending part of seatpost with sand, and pack it in there tight by inserting the hardwood peg, upending the whole 'lever', and bouncing the hardwood peg a few times on the ground. That done, I finally got to unite the lever with the anchor.
Image
Nothing between them but about 3" of sand-filled seatpost. Then it was just a question of lifting the lever about 45degrees. Job done. Here is the result- plenty ripples at the back, but a surprisingly fair curve at the front. A little bit of scarred chrome-plating.
Image

So now I was off to L(ish)BS to get one of those old-style saddle-clamps. Two quid. The seatpost itself was a fiver, so my new seatpost cost seven quid. Post and clamp together weigh about 30g. more than the old alloy post, plus whatever the 14mm spanner I now need to carry weighs. I can live with it if I don't have to sit on rivets all the time. Here is before and after pics.....
ImageImage

I reckon an improvement, functionally and aesthetically. A few things: With the rail-clamps below the 'bolt', as in the photo, the very top of the seatpost was digging into the leather, and the saddle rails, where they converge in front of the seatpost, foul on the sides of the seatpost itself, preventing any further adjustment of the saddle backwards.
AFAICT these issues would all disappear by having the rail-clamps above the 'bolt' instead, but it probably looks better the way it is in the photo. As it is, retensioning the leather of the Brooks (it sure needed it) was enough to provide clearance between it and the top of the post.
With the top of the seatpost closer to horizontal than to vertical, you really need to get the clamp tight on the post to prevent the saddle falling over sideways, probably more so with the rail-clamps above the 'bolt'.
I don't have an account with the CTC forum, so if anyone does, and wants to share my experiments with others with the same problem, here's one relevant thread: http://forum.ctc.org.uk/viewtopic.php?f ... 7&start=75


Top
 Profile  
 
PostPosted: Fri Oct 18, 2013 10:08 am 
Retro Guru
User avatar

Joined: Mon Sep 24, 2012 9:10 pm
Posts: 669
So this morning I reversed the clamp to get the rail-clamps above the bolt, and, as I suspected, the 'issues' disappeared. It actually looks better this way,too, IMO..Here's a picture of the saddle close to as far back as you can legitimately get a Brooks Pro. This is a 23"(c-t) 73deg. parallel frame. The nose of the saddle is now 3 1/2" behind the bottom bracket centre, and with it that far back, I'm beginning to appreciate the 17" chainstays on this frame! You might appreciate the fact that Torqueless has belatedly remembered that the camera is set to manual focus.

Image
Bear in mind also that this saddle has been re-tensioned since the original 'before' photo above, so it's maybe a 1/4" longer in the nose now. Without the re-tensioning, the nose would now be 3 3/4" behind the bracket. I reckon you could get to 4" with a bit of clamp-fettling.


Top
 Profile  
 
PostPosted: Fri Oct 18, 2013 10:49 am 
Retro Guru
User avatar

Joined: Wed Apr 25, 2012 2:08 pm
Posts: 2186
Location: Shrewsbury
Very good.

But I had a tree fall down in the garden and I whittled this out of it.....

Attachment:
Renovo-R4-Pursuit-Wooden-Bike-10.jpg
Renovo-R4-Pursuit-Wooden-Bike-10.jpg [ 112.45 KiB | Viewed 194 times ]


Attachment:
Renovo-R4-Pursuit-Wooden-Bike-9.jpg
Renovo-R4-Pursuit-Wooden-Bike-9.jpg [ 115.69 KiB | Viewed 194 times ]


:lol:


Top
 Profile  
 
PostPosted: Fri Oct 18, 2013 11:45 am 
Retro Guru
User avatar

Joined: Mon Sep 24, 2012 9:10 pm
Posts: 669
Those Mahogamaplepadouk-laminate trees are rare indeed, Robbied. You are beyond fortunate to have one deliver itself into your workshop thus, not to take anything away from your skill with the whittling-knife..

Anyhow, I've just been for a test-ride. I moved the saddle down after 100m, up a bit sometime later, and so on, until it was just right. I also slackened the nose-bolt on the Brooks a bit to let off some of the tension I applied yesterday- your probably not supposed to do that, but my saddle came without the Brooks rulebook, so... better. I'm still up for that 4" though...


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 4 posts ] 

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 10 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

About Us

Follow Retrobike

Other cool stuff

All content © 2005-2015 Retrobike unless otherwise stated.
Cookies Policy.
bikedeals - the best bike deals in one place
FatCOGS - Fat Chance Owner's Group

Powered by phpBB® Forum Software © phpBB Group