I am planning on building one of these (although mine will not look nearly as finished and nice as this lol) and I was wondering if anyone has build one before or used one and would have any advice for me?
The main challenges I think it will pose is trying to get some machined threaded parts to fit into the bottom bracket to protect the frame although I have considered using a piece of wood in the bottom bracket to protect the threads in there. I don’t know if that will be hard enough to stand up to the kinds of forces this thing will be pulling though, it’s not a precision tool that’s for sure. Not really sure who to approach to get a threaded piece like that made.
I also think the actual clamp that holds the seat post will be an interesting challenge, I think it’s probably going to have to be a case of accepting that this tool is the death of seat posts and just drilling through them but I’ve had some ideas for yolks that could be machined to clamp around seat posts and then be bolted onto the actual puller. But again, this is not a precision tool.
by bropdars
10 Comments
You could try using an old bb to protect the threads. Then you just use a threaded rod or some kind of bar to go through it and keep it in place. Saves you some machining cost which can be expensive with such small quantities.
Medieval torture device for innocent bike frames?
[This video](https://www.youtube.com/watch?v=mJ8R_Dqk1u0) goes pretty in depth about making one. Seems like they are just using some kind of “machinable plastic”. Start around the 18 minute mark.
Use a BB rather than machined plugs. Most of the frames you’ll be working with will be BSA. Any other BBs will accept a straight tube so you can make those as needed.
As for the holding onto the seatpost, watch the video the picture is from. Pretty sure it’s Phil Vandely, he seems to have it sorted. My other thought is a prussik hitch with some very static dynema core rope.
I mean, the guy that made the video that you screenshotted this from made one. It’s very detailed as you should know.
Secret tip:
Get an impact wrench (best with a hole in the anvil). Get a hex nut that fits over the seatpost diameter. Cut off the clamp of the seatpost. Bore holes in three sides of the hex nut and thread them with m5 threads. Screw on the nut to the seatpost with some strong screws (not stainless). Fasten the nut to the impact wrench anvil with some brake pad retainers.
Blast it with the impact wrench and pull at the same time. The impact driver should have around 400Nm of power. If yours does not have a hole in the anvil you could pull using a headset wrench that fits over the steerer but does not fit over the nut.
Afaik I invented this tool, I’m loving the impact driver for bikes.
This will unseize seat posts so tight that they would bend the jaws of a bench vise.
I priced welding one up for some of the London workshops, there’s a few different options.
Personally, I was planning on looking for the cheap BBs with removable cups, or even old cup and cone BBs.
For the seatpost, try: “double split clamps” as a search term, you’re unlikely to find them in exactly the size you need, so having them machined to size would be easier.
From the people I know who’ve used them, the handles aren’t the easiest to turn, so longer will be better, but you’re limited by your ability to build a strong handle .
Cut the top off the seatpost, insert a close fitting steel bar to act as a mandrel, file/grind two flats into the seatpost 180* apart, clamp seatpost in a vice on the flats, twist frame off seatpost.
I want to build one where there is the option to turn the seat post at the same time as pulling on it…
Nope.
30-45 minutes of vertical cutting a handful of clearance slits inside to out in the seatpost after lobbing off all but the top inch does it with *zero risk to the frame*.
Draft two of the slits like a keystone & pop it out, squeeze the remaining C profile together and move on to cleaning & lubing for a new seatpost.
The only reason I might consider a contraption like this is if the seatpost is worth more than the frame.