BentAero
Well-Known Member
The idea of a "boom restraint" came to me like a lot of things in life; after a mishap. While preparing for a ride, I leaned the seat against my thigh then bent down to check something on the rear wheel. *WHAM* That horrible crunching sound after the front boom pivoted to the right was my Force 22 Yaw front derailleur slamming into the edge of the seat hard enough to crack the clear coat on the pan -and completely screw-up a perfectly adjusted derailleur. Needless to say, I was NOT happy. Something had to be done to make the front end behave.
My goal was not to create a 'steering damper' as some others have done, but merely install a limit device to keep the boom from swinging all the way left or right.
Enter the Boom Restraint.
I used a piece of Delrin, turned it on a lathe into a spool shape, then drilled a hole for a 5mm bolt.
I then got real brave and drilled a hole in the frame to install a 5mm Riv-Nut. (Just like the ones on the underside of the Steer Tube for mounting a water bottle cage.)
To install a Rivet-Nut, you'll need a tool similar to this one along with the metric adapter and inserts:
It looks a lot like a common Pop-Rivet tool, but costs 4x as much.
Riv-Nut installed.
Once the Delrin spools were installed, it was then some trial and error with different O-rings to get the correct tension. By varying the quantity, diameter, and thickness of the O-rings, you can adjust the amount of tension you like. The end result:
I put 300 miles on it last week on a 5-day tour (DALMAC) and I'm very, very pleased with the result. I can now hold the bike by the seat/headrest and move it around, lean the seat against a post at a rest-stop, easily load/unload from the back of a vehicle, etc. without the front end flopping to one side. With the O-rings I have on it, the boom will move about 45 degrees from center before stopping if I let the boom 'flop'. I never even notice the resistance when making a tight turn or U-turn.
As a bonus, there is a small steering-damper effect as well. Not much, but it is noticeable. Again, a damper was not my goal, but it does smooth the twitchyness a little.
For me, it's a keeper.
My goal was not to create a 'steering damper' as some others have done, but merely install a limit device to keep the boom from swinging all the way left or right.
Enter the Boom Restraint.
I used a piece of Delrin, turned it on a lathe into a spool shape, then drilled a hole for a 5mm bolt.
I then got real brave and drilled a hole in the frame to install a 5mm Riv-Nut. (Just like the ones on the underside of the Steer Tube for mounting a water bottle cage.)
To install a Rivet-Nut, you'll need a tool similar to this one along with the metric adapter and inserts:
It looks a lot like a common Pop-Rivet tool, but costs 4x as much.
Riv-Nut installed.
Once the Delrin spools were installed, it was then some trial and error with different O-rings to get the correct tension. By varying the quantity, diameter, and thickness of the O-rings, you can adjust the amount of tension you like. The end result:
I put 300 miles on it last week on a 5-day tour (DALMAC) and I'm very, very pleased with the result. I can now hold the bike by the seat/headrest and move it around, lean the seat against a post at a rest-stop, easily load/unload from the back of a vehicle, etc. without the front end flopping to one side. With the O-rings I have on it, the boom will move about 45 degrees from center before stopping if I let the boom 'flop'. I never even notice the resistance when making a tight turn or U-turn.
As a bonus, there is a small steering-damper effect as well. Not much, but it is noticeable. Again, a damper was not my goal, but it does smooth the twitchyness a little.
For me, it's a keeper.
