Super-Sized Office Chair Wheels

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Gave my Herman Miller Aeron Chair a 2" lift using scooter wheels and a custom designed 3D printed caster housing.

• There is an ergonomic reason for this project that I'll explain later

These are amazing chairs, and to be honest, one of the few expensive items I own that definitely warrant the high price. Luckily I didn't have to buy it myself, my employer did, but I gladly would have if I'd known it would help with my back problems and especially last this long.

Herman Miller Aeron Chair Website

Supplies

1. Scooter Wheels
2. 8mm Bolts, 90mm Long
3. 1/8" Spacers (Similar Sized Metric If You Can Find Them - I Couldn't)
4. 8mm Nylon Lock Nuts

TOOLS:

1. 3D Printer
2. Standard Hand Tools For Tightening The Bolts
3. 7/16" Reamer (Optional)

Step 1: 3D Print the Caster Housings

This was designed in Fusion 360, and printed via CURA under the standard (.2mm) PLA settings, with 75% infill and if printed in the orientation shown above it will require no supports.

• Each one took about 11 hours and consumed 118 grams of filament
• The axle hole is 8mm to match the scooter wheel bearings
• The caster post hole was sized for standard caster wheel posts, which are 7/16"

STL File attached below.

Step 2: Gather the Parts

Shown above are all of the parts needed to build 5 casters.

1. The wheels are made for scooters and have a 100mm (almost 4") diameter. These were actually the cheapest I could find at around $6 each. Which doesn't sound bad until you realize you need 10, and oh by the way, they come in packs of 4 for some reason (Don't scooters have two wheels?). But the color and design is perfect for my taste (I love green!)
2. Custom designed and 3D printed caster housings in black (I would have printed them in green but ran out of that color filament and its now on back order.)
3. All hardware was purchased from Ace Hardware

ERGONOMIC REASON:

There is actually a very important reason for the larger wheels. When I first got the chair, it did not go up high enough for me to comfortably rest my arms on the desktop. I'm 6'4", so I have long legs and arms. These larger wheels boost the seat height almost two full inches. The Aeron chairs do come in larger sizes but they are uniformly larger, which would not help for my stature. By only lifting the chair, the larger wheels placed my seat at the right height, while keeping the armrests at a height that they will just slide under my desk.

Early on, I purchased these: Giant Caster Wheels

Those served me well for many years in the office environment where there is that low pile carpet, but now since I'm at home in my office with wood floors, they didn't do so well. Thus, the actual purpose (besides just looking cool) for this project. And the timing couldn't have been better for the Super-Size Speed Challenge.

Step 3: Wheel Assembly

1. 1/8" bronze spacers go between the wheel and caster housing
2. Tighten the 8mm bolt/nut just to the point where there is no side play in the wheel assembly. Check the wheels for free motion. You might need to slightly back off the nut if you over-tightened it.
3. Reuse the caster posts from the wheels you are replacing. They are generally held place in by a friction fit of matching grooves in the post and wheel. They can be REALLY difficult to remove. My solution was to put the entire caster in a vise, then grab the post with a pair of vise-grips, and finally use a hammer to smack the vise-grips.
4. Clean the posts and re-grease both the side that inserts into the caster housing, and the other side that goes into the chair legs

NOTE1: I didn't design in the groove mentioned in step 3 above for two reasons. Any stresses like that applied to the 3D printed part is not a good idea. Second, it would have been sized for the oversized wheels I was replacing and not the more standard size length posts. This way, standard size posts or the longer length of the ones I used will both fit.

NOTE2: Because there is no friction fit of the wheel assembly into the chair legs, be careful when lifting the chair as they may fall out. As long as the chair is not lifted off the ground, it will function as normal.

TIP: I used a 7/16" reamer to clean out the post hole. All five of the 3D printed caster housings had burrs and minor stringing leftovers from the 3D printer. Nothing out of the normal, especially for such a large print, but cleaning the holes with a reamer improved the part by easing the post insertion and also not allowing any residual stresses in the part if you were to force the post in without reaming the holes.

Step 4: Finished

Above are a few more pictures of the Before & After.

Thanks for taking the time to read through my Instructable. Please send me any questions or comments you might have. I try to answer them all. Stay safe and healthy! Happy Printing & Telecommuting!