The Arm

Version 1.0

The original arm. Based on the rudimentary designs readily available. The emphasis here is the lowest possible costs - in early development and on a limited budget I was reluctant to employ the mechanisms used in the later arms.

The hand is also the original “Jesus pin” quick-release type.

Version 2.0 / 2.5

This is the update to the V2.0 arm. The internals have been redesigned, and the removable outer shell has been implemented. There are fewer machined parts and more 3D-printed parts.

This is the first arm in which the improved quick release is used. The hand no longer being comprised of machined parts, and instead being a single 3D printed composite part.

Version 3.0

In the current arm, the bulk of the internals from v2.5 are carried over and the internal and external 3D-printed parts are revised.

The hand, still a single 3D part has some minor changes to increase the range of movement at the wrist.

The Arm v1.0

“Don’t spend any money”

I needed an arm, both quickly and on a very limited budget - so v1.0 fit those requirements/limitations.

This is a very simple mechanism but lacks a range of movement, or the range of movement I felt was necessary.

Some basic 3D printed test parts, an old mop handle and I was ready to start testing.

Hands

Designing and making the arm was the easy part, the hand and/or the quick release was the challenge. The hand I ended up with was adequate but not perfect. The quick release functions as it should, but there was a middleman in its operation.

I only had this quick release fail me once - with it releasing when I did not want it to while riding my bike. Mildly terrifying, but easily recovered and ultimately the incentive to build a better hand.

Previous to this first hand, there were many designs and 3D-printed attempts. A lot of testing and a lot of failures.

v1.0 testing

In the end, the v1.0 arm and hand were used to get me through testing for my license. I believe this arm/hand combination went on to do about 20000 km of riding without failure and is now stored away in the workshop.

Pro’s;
Cost-effective design.

Con’s;
Limited wrist articulation (roll).
Limited Elbow flexion.
It's not the prettiest arm to look at.
That quick release.

The Arm v2.0 / v2.5

Now I have money…v2.0

Being a workaholic pays off and I now had enough funds to run with my original mechanism for the arms elbow - giving me the greater range of movement I wanted.

The arm is built, and it functions well…. but, the arm is still not good to look at. And, I was still using the original quick release.

Pro’s;
Greater range of movement.

Con’s;
It’s still not pretty to look at.
Costs - expensive to manufacture.
Still using the original quick-release.
Weight - its heavy.

Making the arm pretty

Version 2.5 was a completely new arm, but retains the same mechanism used in v2.0. The chassis is lighter by 500g and more compact - no more struggling to get my jacket on.

The best part was the removable outer shell. This is all 3D printed, fibre-impregnated, nylon. This outer shell is tough and light, but it can be removed and replaced with different styles and colours.

v2.5 arm was the first arm to use the revised quick-release and simplified, 3D-printed hand. This quick release is lighter, far more simple and adjustable for the load under which it will release. No more accidental releases and getting on/off the bike is easier.

Pro’s;
Reduced costs
It’s starting to look prettier

Con’s;
It could still be a bit prettier to look at.
It could be lighter.

Quick release crash tested

Not that I enjoyed having another motorcycle accident, but it was somewhat of a relief that the quick-release functioned as designed.

The arm, hand, quick release and even the outer shell faired well after the accident, with no damage to the chassis or working components.

Crash testing - complete. No more crash testing is required.

The Arm v3.0

Cosmetic changes & tweaks

There were a few things I wanted to improve, internally and I wanted to adjust the hand slightly. While I was there I created a new outer shell.|

Less visible fasteners, with the advantage of an easier-to-remove outer shell. I did spend some time modelling different shell designs - aiming for something more organic in appearance, but my strengths are in parametric modelling so I ended up with a slightly different look to the v2.5 arm.

Hands, quick release and bikes

The arm, the new hand and the internals were all working well with the bikes I had at the time. After the purchase of my 2024 Z900 a few things needed slight adjustments. The hand’s outer profile was adjusted, the quick release was altered to increase grip strength and the internals were shifted slightly.

I have limited muscle strength in my deltoid, so the wrist roll is limited to suit - the arms wrist roll capability is limited to more of a two-position set-up currently. I switch between positions to suit the bike I’m riding at the time.

Version 4.0?

Maybe. I would like to replace the core chassis aluminium components with carbon fibre and delrin to reduce weight further.

I’m back to being a workaholic for now, as well as focusing on another more advanced prosthetics project, so time is limited.

I’ll see how I go with free time, maybe spend some time learning to surface model and redo the outer shell one more time.

Pro’s;
It’s prettier.
Some weight was shaved off.
Suits a greater range of motorcycles/riding positions.

Cons’;
It could be slightly more pretty to look at - needs a new style.
Some more weight could be shaved off with the right materials.