Custom Piaggio MP3 scooter rack nearly complete!

Cześć, merhaba, and hello, everyone!

(This blog post will likely only appeal to hardcore gear-heads, so those not interested in the construction and technical details of Ara's custom carrier (or "rack") for the Piaggio MP3 250, designed for her 2008 Chevy Tahoe Hybrid, should bail out now.)

Guest blogger Michael (Level-Two Tech Support, Base Camp Manager, and Eighth-Level Geek) here! Ara has mentioned previously we are working with Mike Huspen at Fab-N-Weld to fabricate a custom carrier for the scooter. Today, we went to see the latest incarnation, and I've got to tell you, the artistry and simplicity of its design has me all gooey in my slacks. We couldn't wait to tell our faithful readers about it (unfortunately, the only camera available was Ara's iPhone 3G, so the pictures are less-than-stellar; we'll take better shots soon, I promise).

We've worked closely with Huspen on a number of other projects so he his familiar with Ara's limitations. Thus, the leading design principle was that no strongman tactics would be required to get the bike on to the carrier, or to batten it down once on the carrier. Beyond that, Ara gave him a fair amount of freedom with this project, outlining problems she saw and letting him determine the best way to solve them. Suffice it to say, the direction Huspen took has received the full thumbs-up from Ara!

Back in April, we looked at the 1st-gen carrier Huspen created, and could see things were definitely moving in the right direction. The carrier was designed with a platform atop a central fulcrum, with the "default" orientation of the platform being as a ramp. The idea was that Ara would drive her scooter up on to the platform, and the weight of the scooter would cause the ramp to tip up to a horizontal orientation. Then, while still sitting on the scooter, she would reach over and tighten a pin to lock the platform, dismount, and use ratcheting tie downs — hooked to rings welded to the platform — to secure the scooter in place for transport.

Custom Piaggio MP3 carrier, v.1.0.
Huspen (left) studies the angles;
Ara (on scooter) waits in position.

Huspen got a number of things right on the money with the 1G carrier. Sufficient space between the innermost edge of the carrier and the Tahoe's bumper allowed Ara to shimmy in and open the rear lift gate. The lift gate had plenty of clearance to open, too, even with the scooter on the carrier. Carrier width was even within DOT limitations. He really did his homework.

Nevertheless, there were some issues*. The combined weight of the carrier plus the scooter is upward of 600 pounds — aggressing the maximum tongue weight for the 2008 Tahoe Hybrid. Considerable thought was given to reinforcing the factory hitch/tow bar assembly, but this idea was discarded**.

The paltry hitch ratings for
2009 Chevy Suburban half-ton K1500 LZ,
identical to those for the 2008 Hybrid Tahoe.

Ultimately, Huspen bolted a second receiver tube to the bumper/tow bar. An extended pintle goes in to this second receiver. Once the main carrier is mounted in the factory receiver tube, the extended pintle bolts on to the carrier, forming a single unit. This setup will help resist carrier torsion and also distribute the tongue weight over a larger portion of the bumper/tow bar.

Custom Piaggio MP3 carrier, v.2.0,
featuring dual-pintle anti-torque design (patent-pending).

Another exquisite feature of the 2nd-gen carrier was the addition of a DC winch to pull the scooter into place. This eliminated a number of balancing and safety concerns we had around Ara riding the scooter up on to the ramp*. Now, all Ara has to do is lock the front fork, attach the winch hook, and gently pull Michi up the ramp!

The one-ton, DC-powered winch. In its final iteration,
the cord(s) will allow the controller (itself out of frame)
to unplug from the winch for stowage inside the vehicle.

Huspen wisely chose combination tail lights with stop, turn and tail lamps that feature illuminated side markers. Carrier 1G had the lights mounted, but no electrical work had been performed; carrier 2G was wired for action.

I got in the driver's seat to turn on the headlamps so that we could test the wiring, and was able to check out the reflective safety tape that runs the entire edge of the carrier. The tape even wraps around the front of the carrier so that the driver can see exactly where the sides of the carrier are (see photo below).

Side view mirror perspectives for driver (left) and passenger (right).
Green arrows indicate the carrier's safety tape,
visible even in these images taken with a cell phone camera.

We plugged in the wiring harness and gave the turn signal a go. (Click on the image below for a 770KB animated version!)
Very exciting. It's in the home stretch! Once the carrier is complete, the next step for Ara will be a trip up to Grand Rapids for a three-hour safety instructional with Pastor Freak's son, a one-on-one class customized to her own specific needs, as well as the abilities and limitations of handling the Piaggio MP3. Driving the Tahoe up for the lesson (instead of scootering there and back) will not only cut Ara's travel time in half, it will save wear and tear on her personally — not to mention provide a nice road test for the carrier itself!

We welcome any questions or comments you might have about the carrier. As of this writing, it isn't finished, so if anyone thinks of something we didn't take in to account, please speak up! Thanks!


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Notes:

* Many of the issues we encountered with the 1G carrier had to do with the intricacies of Ara's primary disability: her lack of an abdomen. Although she is fine balancing on the scooter while she is riding it, the delicate process of trying to drive the scooter up the ramp was a problem. Moving with enough momentum to overcome the ramp lip (and gravity), but without so much momentum that she slams into the roll stop, was hard enough. But those "in-between" moments when the front wheels were on the ramp but the rear wheel was still on the ground were precarious; Ara's feet couldn't touch the ground or the ramp. That put her in danger of falling over. Additionally, once level on the platform, she couldn't lean over far enough to reach the locking mechanism that would secure the platform in a horizontal position. That meant she would have to dismount without the platform being secured — another dangerous situation.
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The locking mechanism,
roughly level height with the receiver tube,
was too far out of Ara's reach.

** Newer model GMC truck hitches have integrated body-frame architecture, where the receiver tube is attached directly to the bumper assembly.
Previously, buyers had the option of a receiver tube attached to a tow bar assembly independent of the bumper, similar to aftermarket models (e.g. Rigid's). An example of this can be seen at Shawn's 2000 Tahoe Limited page. The main difference between the two designs is not so much their towing capacity or distribution, but rather how the receiver tube distributes tongue weight to the frame. The aftermarket-type receiver tube/tow bar setup attaches to the vehicle at numerous points, distributing the load over more of the frame; the integrated receiver tube is essentially attached at one point only: the center of the bumper. A vehicle's bumper is designed to be a crumple point upon impact. On the Hybrid Tahoe (and the 2009 Suburban), the bumper is attached to the frame at its ends, allowing for some degree of flexion at the integrated tube. Reinforcing the bumper tube would not be a straightforward endeavor, as there are at least two fenestrations in it already (one each for the receiver tube and the wiring harness). Reinforcement could also compromise the safety of the designed crumple zone, and would require a major disassembly process… so this approach was set aside.
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