Designing-a-replacement-part-for-my-truck.md (4171B)
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- date: 2020-03-25
- title: Designing and 3D printing a new part for my truck
- layout: post
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- I drove a car daily for many years while I was living in Colorado, California,
- and New Jersey, but since I moved to Philadelphia I have not needed a car. The
- public transit here is not great, but it's good enough to get where I need to be
- and it's a lot easier than worrying about parking a car. However, in the past
- couple of years, I have been moving more and more large server parts back and
- forth to the datacenter for SourceHut. I've also developed an interest in
- astronomy, which benefits from being able to carry large equipment to remote
- places. These reasons, among others, put me into the market for a vehicle once
- again.
- I think of a vehicle strictly as a functional tool. Some creature comforts are
- nice, but I consider them optional. Instead, I prioritize utility. A truck makes
- a lot of sense — lots of room to carry things in. And, given my expected
- driving schedule of "not often", I wasn't looking to spend a lot of money or
- get a loan. There are other concerns: modern cars are very complicated machines,
- and many have lots of proprietary computerized components which make end-user
- maintenance very difficult. Sometimes manufacturers even use cryptography and
- legal threats to bring cars into their dealerships, bullying out third-party
- repairs.
- To avoid these, I got an older truck: a 1984 Dodge D250. It's a much simpler
- machine than most modern cars, and learning how to repair and maintain it is
- something I can do in my spare time.
- It's an old truck, and the previous owners were not negligent, but also didn't
- invest a lot of time or money in the vehicle's upkeep. The first problem I hit
- was the turn signal lever snapping and becoming slack, which I fixed by pulling
- open the steering column, re-aligning the lever, and tightening an internal
- screw. The more interesting problem, however, was this:
- 
- This plastic part holds an arm in place, which is engaged by a lever in the
- center of the window which folds closed over the truck bay. It's used to hold
- the window in place and provides a weak locking mechanism. When the arm is
- allowed to move freely, it can clang around while I'm driving, and can make
- opening the truck bay a frustrating procedure. I have been looking for a reason
- to learn how to use [solvespace](http://solvespace.com/index.pl), and this
- seemed like a great start.
- I ordered a caliper[^1] and measured the dimensions of the broken part, and took
- pictures of it from several angles for later reference. I took some notes:
- [^1]: Oh man, I've always wanted a caliper, and now I have an excuse!
- 
- Then, I used solvespace to design the following part:
- 
- This was the third iteration — I printed one version, brought it out to
- the truck to compare with the broken part, made refinements to the design, then
- rinse and repeat. Here's an earlier revision being compared with the broken
- piece:
- 
- Finally, I arrived at a design I liked and sent it to the printer.
- 
- I took some pliers to the remaining plastic bits from the broken part, and sawed
- off the rivets. I attached the replacement with superglue and ta-da!
- 
- If the glue fails, I'll drill out what's left of the rivets and secure it with
- screws. This may require another revision of the design, which will also give me
- a chance to address some minor shortcomings. I don't expect to need this,
- though, because this is not part under especially high stress.
- You can get the CAD files and an STL from my [repository
- here](https://git.sr.ht/~sircmpwn/open-dodge-d250), which I intend to keep
- updating as I learn more about this truck and encounter more fun problems to
- solve.