Sawed-off Pump Gun, OR Blackburn Trunk Pump...- Mtbr.com
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  1. #1
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    Sawed-off Pump Gun, OR Blackburn Trunk Pump...

    ...OR "Saturday Morning Pump Porn"

    OR "How to waste a perfectly good Saturday Morning"

    OR "How to waste a perfectly good $13 tire pump"


    For a long time, I've had an itch for a portable tire pump to reside in my bike box that I tote in the rear of my car. I've used the Topeak Mountain Morph, but the guage sucked, as did the $3 Supergo mini pump I picked up this week. A full size pump just rolls around and collides with the dogs and, well, is one more item to carry to or from the car when I move the bike box.

    So I decided to hack off a section of a perfectly good floor pump and make it work.

    My candidate for this operation was a Blackburn Track Pump. The criteria:
    * Cheap: $13 at Supergo
    * Low guage: Nothing to relocate, unlike a pump with the guage mounted near the top
    * Slaped-together shoddy construction: Purposely avoided pumps with threaded barrel ends
    * Cheap!



    Here's the pump unmodified, laying in the trunk junk box I want to tote it around in.

    I figured I'd need to hack about 8" off the barrel to make it fit. Notice also that the piston rod length has about 2.5" to spare (the handle is fully compressed in the photo).

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_1.jpg">





    Two screws hold the barrel's head cap on -- its not threaded on like some pumps.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_2.jpg">



    Using a drill bit as a guage, I took note of the hole size. Two similarly sized holes will need to be drilled once the barrel is chopped down.

    The two square notches don't align with anything on the piston top cap, so won't need to be cut into the barrel end.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_3.jpg">



    Hong Kong Fui!

    Before cutting, I removed the barrel completely from the pump base. Metal shavings = bad!

    Note to self: Stop trying to use hacksaws for jobs like this! The hacksaw blade twisted and wandered, leaving me a curved cut. I resorted to the saw shown, which was barely adequate but did the trick.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_4.jpg">



    Cleaning up the newly cut edge with a Dremel grinding wheel.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_5.jpg">



    Another example of shoddy construction:

    To save a buck during production, the design connects the rod by crimping the steel tube around the narrow nylon waist extending out of the piston.

    This doesn't disassemble easily, and requires some precision Dremel work in order to slice the steel but not melt or damage the piston head.

    I took my time here, slicing the steel tube longitudinally (akin to unzipping a girdle), then gently prying it open to release the piston head from its clutch.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_6.jpg">



    Back to the barrel, I placed the head cap on to the newly cut end, and drilled the two pilot holes for the screws to tap into.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_7.jpg">



    These are the lengths I ended up cutting the barrel and the piston rod down to.

    Due to grease lining the barrel wall, it took more than a casual rinse to get the metal shavings out of everything. A couple of passes with clean rags did the trick.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_8.jpg">



    No heroic attempt to duplicate the crimp job used to secure the piston head to the steel rod. I chose to use a punch and divot the steel tube in a few select locations to hold everything in place. I ended up with a very good fit, and I don't think the piston head is going to be able to work itself loose over time.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_9.jpg">

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_10.jpg">



    Packed for action -- It Fits!

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_11.jpg">



    Pointless waste of time? Perhaps. But it works! The pump has lost some efficiency due to its decreased volume, taking about 45 / 60 strokes to reach 30 / 40psi on a 2.1" tire. Good compromise, though, when compared to a mini pump. And I can leave my good pump at home where it belongs, not banging around in the car with the dust and dog hair.

    <img src="https://gallery.mtbr.com/data/mtbr/500/234077trunkpump_12.jpg">

  2. #2
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    Reputation: singletrack's Avatar
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    That's slick. Good work.

    I too have a bike box for the car and a pump that doesn't fit in it. Hmmmm...

  3. #3
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    Reputation: LBmtb's Avatar
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    Nice work.

  4. #4
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    Nice work. But instead of cutting the piston loose and "moving it up" the rod, couldn't you have moved the handle down--or was it threaded on?

  5. #5
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    Quote Originally Posted by WaveDude
    Nice work. But instead of cutting the piston loose and "moving it up" the rod, couldn't you have moved the handle down--or was it threaded on?

    That was my original idea. I checked out 3 different cheap pumps for this surgery: The Blackburn, a Supergo house brand, and a Pedros. It looked as if the pump handles are on all are either molded or glued to the handle with no easy way for removal. Once I took this one apart, moving the piston up seemed like the easier option.
    Last edited by Speedüb Nate; 10-10-2004 at 08:07 AM.

  6. #6
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    I'd just get a longer box...

  7. #7
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    Quote Originally Posted by Haggis
    I'd just get a longer box...
    You must have missed the picture of my car...

    <img src="https://gallery.mtbr.com/data/mtbr/515/234077anothersmallcar.jpg">

  8. #8
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    Quote Originally Posted by Speedüb Nate
    You must have missed the picture of my car...

    ROFL!!!

    wicked.

  9. #9
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    <img src="https://gallery.mtbr.com/data/mtbr/516/234077prestige.jpg">

    Round two. The first one worked out pretty well, but I wasn't 100% happy with the pressure guage.

    So I dropped a little more coin on this Pedro's Prestige. The extra twenty bux didn't buy me much -- pretty much the same construction as the Blackburn (prolly outta the same factory from the looks of it), with the exception of a guage with a little more resolution to it. Plus got the purdy orange color to match my Buzz Bomb.

    I did the mod in pretty much the same manner, only this time I used a pipe cutter to split the barrell (instead of a saw).

    v.1 is up on eBay, if anyone is interested.

  10. #10
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    Reputation: singletrack's Avatar
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    Quote Originally Posted by Speedub.Nate
    Round two.
    So didja saw off the dog as well?

    Again, good work. I personally would have gone for a pump with no gauge at all, as the only gauge I trust is the one built into my hand.

    I've got an old Giant pump with a gauge; It likes to tell me I've got 100 psi in my 2.7 Minions.... ignoring that, it fills tires good.


    Anywho, nice job, thanks for sharing.

  11. #11
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    Quote Originally Posted by singletrack
    So didja saw off the dog as well?
    Poor lil guy has a serious case of Napoleon Complex. He tells all the big dogs about it whenever they give him the chance.

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