Dyne's LD-F1 (D-O concept) build

[Dyne]

It's been awhile, but I finally did some more work on LD-F1.  Specifically, I just finished implementing the gear drive system that I mentioned in my previous post.

As a reminder, the old system had a two stage belt drive with 3D printed TPU belts using an HTD5 x 9mm wide profile.  The primary belt had 40 teeth - which determines length of the belt - and had a 3:1 reduction (10T pulley on motor to the 30T pulley on the compound intermediate stage).  The secondary belt has 58 teeth and has a 4.2:1 reduction (10T pulley of the intermediate stage to the 42T drive pulley).

The clearest view of these parts (except the secondary belt) is probably back in post #36.

The new setup would replace the primary belt on each side and the relevant pulleys with herringbone gears (with the same gear reduction, as described in my last post), halving the number of possible sources of slippage.

I printed the new parts some time ago, but I couldn't actually install them until I ordered new M4 hex bolts for use as the axles for the new intermediate pulleys.  Also, I knew installation would require some significant disassembly of the droid's front end (it requires an entirely new front outer wall on each side), so it took awhile to work up the motivation to do it.

Here is the front section of the droid:


The right side has been upgraded, while the left side still has the original parts.  Notice that the right outer wall is a different color than the other black parts (because it's painted, not black plastic).  You can see how much closer the motor sits to the intermediate gear on the upgraded side.  

Here is the new setup.





This shows pretty clearly why order of operations matters for the installation. The remaining belt needs to go around the small pulley inboard of the larger gear. Since the two gears mesh, there's no way to put that belt on once they are installed.  I need a gap to allow the belt to go between them.

So long as the intermediate gear is in place, I can't actually take the motor gear off without removing the motor entirely, and I can't take the motor off (without further disassembly) because the mounting thumbscrews are hidden between the inner and outer walls. Which leaves only loosening/removing the intermediate gear.

Thankfully, I designed the new mounting post for the part so that I'd have the option to put in its axle bolts pointed toward the center of the droid (possibly with a lock nut in a recess between the walls), not just pointing outward as I originally considered doing when I was still thinking of using a long M3 bolt.

Doing it that way means I can loosen or entirely remove the intermediate gear without disassembling anything else.  I don't even need to use that hypothetical lock nut between the walls, since the mounting post can be tapped for the axle bolt and is thick enough to keep the bolt from backing out by itself.  

There's only one issue preventing that...

At the bottom of the last photo, directly below the intermediate gear, you can see where I've started slicing off the support arm for its old M3 axle. This arm is no longer necessary or useful (if it ever was).  In fact, it's actively in the way -- once the front end is actually on the droid, the arm hinders my ability to get a ratchet onto the gear's axle bolt. So it needs to go.


I haven't tested the new drive yet (I need to break out my radio first, and eventually put the tracks back on) but I'm pretty happy with the motion when turning the system by hand.  

With the belts it always required a small effort to start turning and felt sort of ... granular?  Bumpy?  Now it feels smoother and pretty low-effort.  With any luck, that also means it'll slip a lot less.  (My suspicion/hope is that this startup resistance, exacerbated by the full weight of the droid, plus the higher rpm on the motor side, meant that the 10T pulley that was previously on the motor was the most likely place for slippage to occur, not the 10T pulley on the intermediate stage that still exists. But i could be wrong.)

I could still stand to improve the remaining belt's tension, but I'd have to figure out where to cram in an idler/tensioner to do that.  I had some thoughts on that, but I haven't implemented them in this iteration and I'm not sure they are feasible.