Stealthy Bullitt Pump Compartment

There’s a fair amount of usable space under a Bullitt’s cargo deck, space which I don’t think is often utilized to it’s full potential.  A good candidate for making use of this space is small / thin objects which you want to have with you all the time – like your pump and puncture repair kit.

In this article I’ll summarize how I’ve designed and implemented a stealthy compartment for holding such things.

This solution aligns with my guiding Bullitt principles:

  1. The Bullitt should be carrying stuff, not me: E.g. I should never need to wear a backpack.
  2. Peak performance: the Bullitt is a lean machine, so unless restricted by a specific cargo load, the overall performance of the Bullitt should be maximized.  That means nothing that limits speed, handling or cargo carrying.
  3. Elegance: the Bullitt’s fit-out (locks, pumps, bike bags, etc) should be elegant.  Elegance should be the product of following the first two principles, and likewise, by aiming for elegance I should achieve the first two principles well.

General Concept

The concept is to have a hinged compartment that runs along under the cargo deck.  The obvious location is along the side opposite the steering arm – for easier access.  Having it hinged at one end provides a good balance between accessibility and strong mount.

By utilizing the space under the cargo deck:

  1. The exterior of the bike is not cluttered with stuff, which frees up space for other things (both on the frame in general, but also in terms of cargo carrying.
  2. It is not directly visible in most scenarios, so not so obvious to casual thief’s.
  3. It is protected from the worst weather.

Compartment Design

In my case, I only have a thin space available since I already used the central space under the cargo deck for my speaker system (see: Bullitt Boom Box).

I decided my compartment only needs to hold the pump and puncture repair-kit.  I didn’t build it to hold my tools as well – for a number of reasons, one of which is that this is bit of an experiment: start off small and see how it goes.

Above is the compartment, detached from the Bullitt.  On the left is the forward attachment point, through which runs a single bolt with a wingnut; this is how you release the compartment for loading/unloading.  On the right is the top of the rear mounting hinge.  This is permanently screwed to the cargo deck.

The long wooden board provides the main structural part of the compartment, joining the two attachment points, and provides something to secure the pump against.  The rear box-like area holds the puncture repair-kit.

You’ll notice the gap at the rear, between the hinge and the side board, this is to accommodate the Bullitt’s front wheel brake and light cables that run along under the frame. 

Mounting

The rear mounting point is immediately in front of the cross-bar, on to which the kick-stand presses when the Bullitt is parked.

Be aware that the sweep of the kick-stands pads will likely scrape the back of the pump compartment if it’s too close.  Also make sure there’s enough room for any cables to run past.

In terms of the cables, at the front of the Bullitt these should be located to the side, before the run up to the front forks.  This means that there should be enough room for the front mounting bolt on the inside of them.  I then have mine running down the side of the speaker enclosure, in such a way that they are secure but with enough flex to run comfortably along the outside of the compartments long side board.  They then exit through the rear of the compartment.  Make sure that the compartment doesn’t foul on them with opening or closing.

The front attaching position is well forward – just behind the front cross-bar.

Images: left – the rear mounting bolts.  Centre – with the compartment removed, showing the bolts sitting in position ready to take the compartment.  Note the location of the kick-stand (in down position) and the cables running around the back of my custom speaker enclosure.  Right – photo taken from a similar angle, showing the compartment attached.

There are three mounting bolts, all of which are flat-head and counter-sunk.  When mounted, this type of bolt head sits flush with the cargo decks surface, so there’s zero impact to cargo.

My cargo deck is made from 7mm plywood.  This isn’t especially thick, but it will safely hold the counter-sunk bolt head as long as the bare minimum of counter-sink is used (so that as much wood as possible is retained, to hold the bolt head).  Part of the reason I think this is safe is because the load the compartment carries is very light.

Note: depending on your design, I suggest you periodically check the holes, and the wood around the bottom of them, to ensure there’s no wear or weakening – you don’t want the compartment to come loose whilst riding.

The forward bolt:

  • The hole in the deck only needs to hold the bolt in position, the bolt is held fast by the wingnut used in combination with a flat washer and a spring washer.
  • The diameter of the hole in the compartment is such that it slides easily on/off the bolt.

The rear mounting bolts – I’ve used two slightly different approaches for these:

  1. The holes in the deck only needs to hold the bolts in position, the bolts are held fast by the compression due to the compartment mounting.  The same diameter is used for both bolts.
  2. The compartment hole for bolt-A is tight, so that the bolt’s thread bites securely into the wood.  Be very careful not to over-tighten otherwise you risk striping out the wood that holds the bolt secure.
  3. The compartment hold for bolt-B is not tight, the bolt slides through and is fastened by a hex type locknut.

Why the two different approaches?  Basically it’s bit of a hack and an experiment. making the wooden hinge was much trickier than I anticipated – the one you see is about the third attempt.  The wood used is strong enough but I managed to break the first one whilst working on it – so I was mindful not to over-stress the wood.

I also wanted to maximize the strength of the hinge, which meant having enough thickness to secure the metal hinge, side panels and so on.  Using this combination seemed to work the best based on my first two attempts.

Bolt-A provides the most timber for strength of the unit, whilst bolt-B provides the most secure fastening due to the locknut.

In Closing

The position of the front bolt is such that it’s fairly easy to access the compartment, but it is a little bit fiddly to re-attach.  It’s definitely convenient enough for occasional use but it’d be nice to have a slicker design if you wanted really frequent access – and don’t forget to manage the Bullitt’s cables.

The pump is secure sitting in the compartment, but I also use a piece of rubber to tie it to the side board so that there’s no rattle whilst riding.

I’ve had this in operation now for around 6 months and all’s going well.

If you don’t have a speaker system under your deck: (a) you should get one :P, and (b) you will have more flexibility in terms of your compartment design and what you can accommodate in it.

 

 

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