(I don’t drink beer, sorry-not-sorry.)
Overthinking time! Today: Throttle locks.
Have you ever done a ride so long, your right hand is left useless? For those gaudy fucks who have cruise control (real cruise control) I salute you with my erect middle finger. For the rest of us mortals who have a bike with no lavish fly-by-wire throttles, there are other solutions.
You have fancy ones:
Less flashy ones:
And things you should not even use to clamp a sub’s dick to a wall:
But, and it’s a big BUT, I have realized they are all wrong, because, you see, they put the control in the same hand that you want to block. What you really want is to lock/unlock with the left hand, leaving the right alone to do it’s speedy-speedy/stoppy-stoppy thing. And no, using your left hand to hold the throttle is definitely stupid beyond even the shittiest throttle holds. /transfers over the connection and SLAPS YOU for thinking that/
BUT, how, you might be asking, can one accomplish that? (you are probably asking why, instead, but I don’t give a fuck.)
Well, my CB500x has a continuous tube handlebar, wich means I can run a bowden tube through all it’s lenght and connect something on the left side, to something else on the right. Easy.
A bit of drawing later:
So, at first I tried to just cable actuate a similar screw-clutch type than the more streamlined locks, but that proven complicated by requiring both a 90º vector turn in the cable with no micro-pulleys avaliable, and too much lenght of travel cable-wise.
A printed test model:
I must admit It did work to an extent, but that was not the bestest way by any means, I knew well before even finishing the print. Meanwhile I was waiting, I happened to discover that the throttle handle body, at least in my particular model, happens to go beyond the end of the metal tube that holds it. I could definitely use a drum style brake in there once I had tested, and failed, with the first idea.
Since I needed measurements from the various internal diameters, I decided to bite the bullet and dissasemble the counterweights in my own bike. You can’t imagine my face when I saw that this was inside the handlebar:
I had always assumed the thing was just the outher portion you could see, attached with some kind of inclined plane nut (like the first model at the top of this post), but nooo, it had to be massive and hidden away and act as a surprise when I decided to overengineer a stupid thing in it’s place.
Oh well… ¯\_(ツ)_/¯ …in any case, that is just an elongated nut to add mass, back to the studio:
Damn, this thing looks like a German WWII grenade.
So, this is the drum brake thing implemented on the right, throttle brake side:
The central plunger separates both halves that contact the white nylon drum in the throttle grip, braking it.
But, you might ask, does it actually work?
Well shit, yes it does, shut the fuck up already.
Here’s a video of the brake shoes moving (white piece is teflon for maximum slipperness):
The rubber band is just to hold them. They can’t fall once installed. I did implement a groove to leave the rubber permanently in there, but that would also reduce the braking surface, and as said, once installed, they won’t go anywhere. (Think of it like some bearing retainers in those flexible clutch/brake levers that can fall down when you work on them, but won’t once finally installed).
On the controller side, I really want to look both unconspicuous AND simmetric to the other side, so I made the effort of operating the cable pull using the existing sleeve coupled to a rotary inclined plane:
That inclined plane piece links to the outside grip cover with a passing headless screw.
Should you where been paying attention, you might be asking by now: “What is that weird groove in the bottom of the cross-sectioned piece?”
This one, you unattentive bitch.
Well, as I told before, this is a bowden driven mechanism, that means that somewhere in the piece there is a cable and a sleeve that run along the thing. But this also has an angled nut to retain itself in the handlebar tube. Unfortunately, those types of nuts have the bad habit of twisting around until they are fully locked, and that would put the bowden in immediate risk of shear.
To prevent that, an antirotation pin was added, and it’s seat in the nut elongated, so it can move up and down when tightened/loosened. Said pin also doubles as axle for the brake pads to pivot.
Here’s a frontal view of the bowden/pin interaction:
When the screw is loose, the amount of play built in the front piece means that the nut top groove for the bowden tube can’t go above the shear line. As you tighten it, the nut can only go down (in the graphic) and also can’t rotate, keeping the bowden safe at all moment. The pin would act as downward limit for the nut, but you should not be using this in a tube whose diameter is so much different than the nominal diameter of the piece.
Pretty nifty if you ask me.
Since I was at it, I decided to go all fancy out and make the parts to be the same for both the left and right sides for TWO reasons:
- Why not?
- I can.
- Surprise, motherfucker!
Actually at manufacturing is easier if I have to make more of only one model, albeit slightly complex overall, instead of different models. That can streamline the machining process a lot.
As for holding the outher grip pieces in place, I made simple ring clips and recesses on both sides of the piece:
It’s a shame I can’t use steel wire that looks like enamelled copper, the color contrast would be wonderful. With a copper ring the sleeve stays in piece really well, but still can’t risk it in road conditions.
Unfortunately, the cable puller piece has to be machined out of metal even for this test.
The pressure required to hold the cable with that little vertical M2 screw and withstand the pin sliding in the inclined plane would be too great for the PLA to hold. That will have to wait for the next chapter of the adventure.
For now I’ll leave you with a size comparison between the metal counterweight and the 3D printed model.
No, I didn’t print the longer nut because that would be a waste of PLA and it doesn’t add anything to the mechanical requirements for a test.