Pogies for aerobars

Motivation

• my commutes these days are about 5-9 miles long & I find it faster & more comfortable to stay in the aerobars 95% of the time, the exceptions being

  • rough roads with potholes

  • slowing down/using brakes

  • delicate maneuvering through traffic

  • shifting gears

• regular flat bar mitts were indeed warm, but

  • cumbersome to mount

  • my position is less comfortable on the bike

    • more upright, which meaningfully slowed me down

  

  • while indeed I could get away with thin gloves with bar mitts, not only is it far too cold to use such thin gloves on the aerobars, but it's very unsafe in that I can't easily get to the brakes if needed

    • it's also a real pain to shift gears

• this train of thought motivated the creation of aerobar pogies

Constraints

• quick access to brakes for safety

  • this necessitated having the sides at least open quickly, even if that included breaking them somehow

    • ideally, they'd also be easy to close – especially one handed so that stopping the bike & dismounting was not necessary

• easy mount & dismount: mounting & dismounting Bar Mitts on drop or flat bars is a real pain

  • thankfully aerobars are fairly easy to mount to

• aerodynamics are not a consideration & more of a bonus if anything

  • I'm fairly certain that being in this position is a net positive compared to bar mitts & sitting upright

Construction

it's essentially a box-shaped frame with a skin over it:

Mounting

• designed around Profile Design T3+ aerobars, but could be adapted to work with others

  • I took some rough measurements & generated this CAD:

    

• shown above is a section view

  • the MOUNTING PLUG, shown in grey, simply slips into the ends of the aerobars, or the skis as I call them

• The overlap is designed to be 50 mm, which is stable without any other locking mechanisms

  • this works out well because

    • unseating 50 mm is practically impossible with any normal crash, & even if it did, you'd probably already be thrown off the bike & have greater problems to contend with

    • it is extremely fast to mount & dismount

    • N.B. due to a design oversight, it's actually slightly difficult to remove because I didn't plan for clearance on the reverse side of the ski

      • in practice, I do have to bend a bit of the plastic to remove the box, but it's fine & I'm too lazy to change it until it breaks

Attaching the box to the mounting plugs

• This joint is made with M6 hardware

  • the max useful screw length is about 78 mm

    

  • this way, the screw itself works like reinforcement, like rebar

    • to maximize this benefit, the mounting plug would ideally have tapped threads so as to maximize contact to share loads with the screw

      • I'm currently using an older version (rev 6 i think) which uses simple brass heat set inserts + a clearance fit around the screw which is far weaker but seems to be doing well anyways

  • designed for an M6 button head screw with loose clearance fit in the front panel such that the front panel can compensate for skis not mounted exactly at the right spacing width-wise)

Cover

• possible materials

• ESD mat

• Neoprene

  • Mouse pad

  • Keyboard mat

• Cardboard, with coating to make waterproof

• Campaign signs, coroplast

• For static covers, print a thin skin

  • Might crack over time

Hinge mechanisms for the sides

• any rigid panel + TPU living hinge

  • this would require some kind of integration/joint

    • I don't have easy multi filament printing ability, but this could be well achieved with this interlocking feature in Cura

• any rigid panel + magnets

  • magnets would also have supreme ease of being able to close the sides one handed while riding

Iteration

Early iterations (rev 4)

• my early iteration was a paneled box with a front, back, & 2 sides

  • no joinery, just M5 hardware used to bolt everything together

  • due to a design oversight, this meant that I could not extract my hands from the aerobar position to my brakes in a straight line; I'd have to pull straight out of the box first, then go to the brakes

  • because of this, I tabled the project for about a year before the latest revision

• I stretched 2 plastic shopping bags over the frame & used a really big hair tie-type elastic band to secure the bags into a channel printed in place

• the bags were absurdly noisy in the wind

• the front was also made with about a 10 x 10 mm square cross section for the beams, which experienced a lot of torsion

  • therefore, I wanted to fix this by stiffening that area in the next version, as well as trying to reduce the mass cantilevered about the mounting points

Latest iteration (rev 12.1) as of 2024-02-18

• uses dovetail joints & M3 hardware (qty 6 CSK screws & square nuts to join the major panels)

  

  • top used 0.2 mm clearance which was a little loose

  • bottom accidentally made with 0 mm clearance, but able to force it in

  • should really be 0.1 mm clearance

• uses a cover which is flexible but somewhat rigid to mitigate flapping in the wind

  • optionally waterproof

  

• the various holes on the top & bottom panels (yellow & red) are for M3 CSK bolts & nuts, which were provisions for attaching smaller pieces to hold the windblocking front cover in such a way that

  • it wouldn't flap in the wind

  • I could reversibly break open the cover to reach the brakes

    • I could reseat the cover one-handed while riding

  • in practice, the cardboard I used for the windblocker simply doesn't flap in the wind, & I believe that by designing in mild interference (0.5-2 mm) along the edges with the top & bottom panels, the friction alone would be sufficient to hold the cardboard in place

Windblocker

• I printed this out 1:1 & used it as a template to cut a piece of cardboard out

  • PDF attached

• note the bend lines

  • align the bend lines with the corrugations of cardboard

  • score the bend lines with a utility knife but only cut through the first skin of the cardboard, not the second

• rev 12.1 is designed for use with 3 mm thick cardboard

Future improvements

I've been riding with this rev 12.1 “draft box” for about 3 weeks now

• it rattles a little bit, but I can't figure out the exact source

  • the end of one of my skis was mangled in a crash a few years ago, & consequently it's a bit shorter than the other one, so that's my primary suspicion at the moment

• design in sufficient clearance to cleanly remove the box

• design a variant for aerobars where the skis are completely straight

Blocking wind on top & bottom

I found it easier to print a 1 mm thick skin, which is surprisingly robust in PLA. Here is the box depicted upside down & from the inside:

• here is the top

• note that the cardboard windblocker has settled in a slight fan out

  • it still doesn't flap in the wind, which is great

• it used to friction fit snugly inside the frame, but now no longer

• I was supposed to use M6 button head screws with a clearance fit in the PANEL, FRONT, but forgot & used CSK screws instead

  • the intent was to allow a small amount of float in case the aerobars were not exactly measuring center to center when I first took the measurements

  • in practice, it worked out fine

Again the inside, showing the various M3 mounting points I never used:

Here is the box mounted into the aerobars:

2024-02-25

• I swapped out for some PLUG, MOUNTING parts printed in Durable resin on a Form 3 & tapped to M6 threads all the way

• this way the long M6 x 75 screws can transfer stress a lot better to the plastic walls