Day: July 1, 2019

Yet another day, we rise to the gentle embrace of the morning sun and the ever-so-familiar song of the “uwu” bird. And of course, the first thought on our minds is that damned clamping mechanism.

Luckily, Qian Xin had delivered us some great news the previous week that we had just been assigned a mentor, by the name of Savior Jie Huang, who’s a CN Yang alumni in Mechanical Engineering and is currently doing PhD studies in the same field. Will he deliver us from the pain of the clearance problem? We walked (or took the bus) with great anticipation for this mysterious hero, expecting him to disseminate nuggets of infinite knowledge to us like a tree dispersing its seeds.

Unfortunately, he was as equally stuck as us on the problem. He suggested some ideas on telescoped arm (basically a retractable arm system), but we had already explored that idea and it’s too commercially difficult to source, not to mention it will struggle with the load. It won’t really help us with the clearance method either.

LUCKILY, he does have some working knowledge of mechanical simulations and SolidWorks, so we passed our assembly files to him for him to tinker around a bit. Our attempts at SolidWorks (while very valiant) had always ended up in the whole arm system disintegrating into many parts due to a SolidWorks glitch whenever we put in the actuator sub-assemblies (they need a length limit so they don’t overextend or overcontract). Not so valiant, I guess.

As for the clamping problem, what we really needed was a new way to clamp the whole unit and avoid the metal wires, the metal handle and the roof of the train…

After Jie Huang left, some slightly better news: the heavy-weights of our lifting system, the linear actuators arrived! These were the 3 x 500mm Linear Actuators (+ 8 Actuator brackets to attach these to the 3060 aluminium profiles)

Wonderful news! We could finally toy around with these actuators…Nope. How could the day go so well? Of course not. The actuators were actually rated 750N, not the 1500N we had selected.

HOWEVER, we also knew that these were for the secondary arm and not the main arm, and the load they would have to support is just that of the pneumatic unit and of course of the secondary lifting system itself. Furthermore, we’ll be using multiple actuators, so their combined carrying ability should be well within safe limits.

As a rough test, we also tried to lift one of the tables in the MnT lab with the actuator ALONE, and guess what, it managed to do it without any problems. That’s awesome news that we didn’t get a faulty actuator.

In some other news (while still thinking about the clearance problem), Tony instructed us to source for more nuts, screws and brackets for the aluminium profiles, as he reckoned that what we bought might not be enough (given that some of them were bound to be slightly defected as well). Thankfully, Terence was around in SPMS, and he readily agreed to us dissembling his prototype, and mind you, that was the best craftsmanship prototype for last year! How gracious of him and his group.

Also, not much new inspiration hit us, so we proceeded with the 2x heavy duty ball joints, which also just arrived. We needed a way to secure the heavy duty ball joints to the whole clamping system. To ensure maximal fit, we decided to custom-design the ball socket instead of buying one. Ideally, this double-ball-joint system would allow us to rotate the clamping mechanism quite freely and also allow the manual sliding motion for the technicians to lock the pneumatic unit into the train.

Our first prototype for the socket looked something like this! The important thing was to make sure that the inner curve of our 3D print fits the ball as much as possible, which it did! Thank you to the Ones above. Our day is slowly getting better.

Before we knew it, it was already 6+ pm, so we decided to call it a day. The clearance problem continued to linger over us, and it was quite clear (pun intended) from our facial expressions. We decided to heed Tony’s advice, and just wait for that “shower” moment. Good bye, for today!

As we overhauled our initial vertical clamping method, we had to rethink all the clamps (gg so much effort).

 

However, with our collective genius (!!!), we managed to create 3 new clamps using toggle clamps and some 3D printed parts. In the creation of these 3 new clamps, we definitely kept some crucial concepts in mind:

1. Secure the stability of the unit with the maximum number of points of contact to stabilize the unit in a 3D space. The unit will likely be rotated 270 degrees about its longest axis and may be subject to some rotation about its short axis across the unit, perpendicular to the unit, due to the rotation of the long unit to fit through the train door.
2. Do not cross the top most bunch of wires as this will cause our clamps to hit the roof of the working space.
3. Clamps must be able to be slid in from the base of the unit without requiring vertical motion. This will enable us to better unclamp and slide our the unit in the working space.
4. Clamps used are restricted to toggle and push clamp connected to aluminum profiles directly or via brackets
5. Power supply housing and wires should be avoided and not directly clamped. Too much force should not be exerted on these sensitive electrical components as they may be damaged.

 

Here is what we have done so far:

 

From right to left, Clamp 1 and Clamp 2 are pictured below:

 

 

As can be seen, Clamp 1 has 2 points of contact. Using the current pictured orientation of the unit as our reference, clamp 1 will prevent motion upwards and towards us.

 

Similarly, Clamp 2 has 3 points of contact. Using the current pictured orientation of the unit as our reference, clamp 2 will prevent motion upwards, towards us and to the right.

 

Clamp 3 is pictured below and it has 3 points of contact too. 2 points of contact to prevent the unit from moving towards us and 1 to prevent the unit from moving downwards.

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There is a direct relationship between the points of contact and the stability of the unit when being lifted. Hence, we are aiming to have at least 10 points of contact for clamps in total when the whole clamping system is done. Since there are already 8 points of contact with these 3 clamps to the right of the CG of the unit, our progress with the clamps seems very promising!!

 

Also, we made progress with solidworks. We created a holder for the long L-shape metal tubing, to be coupled with a clamp.

We first thought of this design below, but realised it was not the best idea to approach and clamp the metal tubing from the top, since we want to avoid any kind of clamping from the top as much as possible given the limited vertical clearance.

Furthermore, it would also not be able to prevent any downward vertical movement of the metal tubing (away from the grip), which makes the unit more prone to becoming loose from this grip.

A much better idea was to clamp the metal tubing from the side using a rotatable aluminium profile. (Please note that the photos were taken from 2nd July’s post, purely for illustration purposes of why we chose this design. On 1st July, we had not yet printed this grip.)

This is how the locked red 3d grip would look like after the profile was rotated clockwise (using an appropriate clamp). This way, the metal tubing cannot drop loose in the downward vertical direction (unlike the previous design). The only can it can become loose out of the groove is if it moves horizontally to the right. Thus, we settled with this second design.

This design will be subject to some adjustments, but the addition of this grip will increase in the number of points of contact for the unit, which is, of course, good news.

Also, we 3D printed and refined the design of the ball joint holder”

Here are our 2 ball joints on top of 3 2020 aluminium profiles. This will make up our double ball joint configuration in between our third arm and clamping system for great adjustability of the clamping system. It works by allowing the ball joints on each side to rotate individually. The combined rotation of the 2 ball joints will allow the whole double ball joint configuration to be especially adjustable.

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