Results 1 to 11 of 11
  1. #1
    donkey
    Reputation: nbrennan's Avatar
    Join Date
    Oct 2006
    Posts
    252

    New question here. Shortening a gusseted seat tube

    I've seen a couple MTBR threads about shortening the seat tube of an Ice Cream truck. I know it can be done, but I've been unable to find a frame builder local to me to do the work. I get the impression its too small a job for someone to make room in their schedule. If that changes I'm happy to support a pro plying their trade. If this experiment pans out I'll likely pursue a similar custom build with a shorter wheelbase.

    That said, I'm considering doing it myself with an angle grinder, hack saw, cutting guide, and drill. I have a pretty good idea of how to remove the necessary material but I dont have a strategy to close the vent hole that I expect to find inside the gusset tubing. Would leaving an open vent hole create a stress riser or any issue aside from exposure to the elements?

    I'm interested in removing to gusset to make room for a dropper post. At the moment I can't quite fit a 125 mm dropper given my saddle height. An extra 1.5" off the ST length should do the trick.

    Happy to post more pictures if that helps.
    Shortening a gusseted seat tube-img_1275.jpg

  2. #2
    mtbr member
    Reputation:
    Join Date
    Feb 2012
    Posts
    35
    Quote Originally Posted by nbrennan View Post
    I've seen a couple MTBR threads about shortening the seat tube of an Ice Cream truck. I know it can be done, but I've been unable to find a frame builder local to me to do the work. I get the impression its too small a job for someone to make room in their schedule. If that changes I'm happy to support a pro plying their trade. If this experiment pans out I'll likely pursue a similar custom build with a shorter wheelbase.

    That said, I'm considering doing it myself with an angle grinder, hack saw, cutting guide, and drill. I have a pretty good idea of how to remove the necessary material but I dont have a strategy to close the vent hole that I expect to find inside the gusset tubing. Would leaving an open vent hole create a stress riser or any issue aside from exposure to the elements?

    I'm interested in removing to gusset to make room for a dropper post. At the moment I can't quite fit a 125 mm dropper given my saddle height. An extra 1.5" off the ST length should do the trick.

    Happy to post more pictures if that helps.
    Click image for larger version. 

Name:	IMG_1275.jpg 
Views:	47 
Size:	60.0 KB 
ID:	1203191
    Angle grinders and frames often end in tears

    Can't you get away with lopping of the ST at the top of the gusset, and brazing on a collar?

  3. #3
    donkey
    Reputation: nbrennan's Avatar
    Join Date
    Oct 2006
    Posts
    252
    Quote Originally Posted by m-gineering View Post
    Angle grinders and frames often end in tears

    Can't you get away with lopping of the ST at the top of the gusset, and brazing on a collar?
    Yeah, an angle grinder seems like a bit of a hack job so I'm wary of doing it. I think I could render it usable but I imagine I'd create a few more problems along the way.

    Taking it to the top of the gusset makes sense, but I dont have the skills to add an integrated collar.

  4. #4
    Bicycles aren't motorized
    Reputation: life behind bars's Avatar
    Join Date
    May 2014
    Posts
    3,644
    If you are confident that you can wield a hacksaw and a couple of files successfully you can do this. Carefully hacksaw the gusset leaving a bit of it. It'll take a couple of different cuts to get it close. Do not cut into the top or seat tube. Carefully finish with a sharp flat file. Shorten seat tube to desired length and square it up with the flat file. Take your time, don't get in a hurry. Since you're going to be touching up paint, a dab of body filler to close up the vent hole. Finish it, prime it with good quality primer and paint it.
    You meet the craziest people riding e-bikes!

    Make
    America
    Gravel
    Again

  5. #5
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    1,076
    In my opinion, cleanly removing the gusset from the TT is probably a more challenging job than the alternative of leaving the brace in place and brazing or TIG welding a new seatpost binder.

    Get an old junk frame and practice with a hacksaw until you are confident with cutting up tubing.

    Example of the binder that you would then need is;
    SEAT BINDER AND BOLT - PREMITERED :: SMALL PARTS :: BRAZON/SMALL PARTS :: Nova Cycles Supply Inc.

    You don't necessarily need a skilled framebuilder to help with adding the binder, most any non-bike welding/machine shop could easily braze or TIG weld the binder for you for minimal cost if you have it all prepped for them.

  6. #6
    donkey
    Reputation: nbrennan's Avatar
    Join Date
    Oct 2006
    Posts
    252
    Thanks for the info guys. There are some good threads about this here on MTBR. Below are the two most helpful links... I think I'll have to DIY this project and post back with results.

    Shortening a Surly fatbike seat tube.

    https://bikingtoplay.blogspot.com/20...y-surgery.html

  7. #7
    mtbr member
    Reputation:
    Join Date
    Feb 2015
    Posts
    67
    I managed to cut my seat tube down on my Boardman FS Pro using a jubilee clip and a hacksaw. Re-slotted the tube and drilled the bottom of it as stress relief. No problem,,

  8. #8
    donkey
    Reputation: nbrennan's Avatar
    Join Date
    Oct 2006
    Posts
    252
    did you use a hack saw to re-slot the seat tube? did you drill the stress relief hole and then cut towards it? i was thinking about using a punch to center the drill bit. I've never done any frame modification so i'm trying to be pretty circumspect about it. Thanks for your input.

  9. #9
    mbtr member
    Reputation: scottzg's Avatar
    Join Date
    Sep 2006
    Posts
    4,958
    Quote Originally Posted by nbrennan View Post
    did you use a hack saw to re-slot the seat tube? did you drill the stress relief hole and then cut towards it? i was thinking about using a punch to center the drill bit.
    That's how i do it. I use 2 hacksaw blades in the saw and saw towards the stress hole. Clean it up with a file.
    "Things that are complex are not useful, Things that are useful are simple."
    Mikhail Kalashnikov

  10. #10
    mtbr member
    Reputation:
    Join Date
    Feb 2015
    Posts
    67
    Quote Originally Posted by scottzg View Post
    That's how i do it. I use 2 hacksaw blades in the saw and saw towards the stress hole. Clean it up with a file.
    That's how I did mine. I cut around 18mm from the length of the seat tube.

    First I marked the tube with a fine sharpie pen, then placed a jubilee aligned with the pen mark. Once tightened up, used as an edge guide for the hacksaw.

    I didn't have enough tube left to extend the original slot, so I added a slot directly opposite the original. Slotted using a hacksaw and followed up with a needle file to increase the slot width.
    You must drill the relief hole first, use a punch to centre the drill.

    I can now use a 125mm dropper.

    Looking at your picture, I don't think that you'll be able to lose much more than 15mm, or you won't be able to use a seatclamp

  11. #11
    donkey
    Reputation: nbrennan's Avatar
    Join Date
    Oct 2006
    Posts
    252
    I plan on removing the gusset as well, so the seat tube will be trimmed to just below where the gusset currently is.

Similar Threads

  1. Shortening a Surly fatbike seat tube.
    By Saul Lumikko in forum Fat bikes
    Replies: 90
    Last Post: 01-22-2018, 10:21 PM
  2. Frame Modification - Head Tube shortening
    By kdonks in forum Frame Building
    Replies: 7
    Last Post: 12-18-2017, 04:53 PM
  3. Seat-post Shortening Suggestion
    By Skids! in forum Tooltime
    Replies: 33
    Last Post: 10-28-2015, 01:17 PM
  4. Seat tube, top tube, head tube deal
    By calstar in forum Frame Building
    Replies: 0
    Last Post: 08-29-2013, 10:12 AM
  5. Sloping Gusseted Frame SeatPost Insertion
    By diegomtb in forum Bike and Frame discussion
    Replies: 2
    Last Post: 06-03-2013, 02:18 PM

Members who have read this thread: 78

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

mtbr.com and the ConsumerReview Network are business units of Invenda Corporation

(C) Copyright 1996-2018. All Rights Reserved.