I’m doing some R&D for some ideas that have been circulating in my mind. Electric motors and batteries are creeping into everything.
For this case, I’m looking at approximately a 40:1 gear reduction in a motor drive line. There would be a primary (??:??) and final reduction (15:40). That means 15:1 for the primary and gearbox. If the primary is a 3:1 reduction, the gearbox would be 5:1.
Primary reduction would be an HTD 8M belt and final reduction via a 420 chain.
Since space, weight, and efficiency are a priority, finding a way to pack everything together tight makes sense. I’m going to need a bunch of reduction. I want it compact.
I took a quick look at buying gears and making a gearbox. This spiraled out of alignment for the project very quickly and pointed to it not being the right directing.
To move something forward I bought a cheap NEMA 23 gearbox from Amazon ($42.19) to experiment with. It’s marked DFL57-L1-5-S-D10. This got something in my hands quickly and can allow me to do some medieval work on it.
Removing the end flanges was obvious enough but the sun gear and carrier remained part of the flange assemblies. The guts aren’t obvious.
The sun gear shaft end was simple enough to remove with a snap ring and a light press. Later this evening, I expect to press the sun gear from the adapter shaft end. Then I can look at integrating my own bearing and shaft assembly. The one bearing on this side is a 6904RS
The sun was removed remarkably easy on a small hydraulic press. There was far less insertion than I was expecting. More, I thought that there’s be some flats to keep from spinning. Typically these will have a tri-flat.
The carrier side was removed poorly. I didn’t remove the oil seal as I would have to have been destructive but that led to even more destruction. It turned out that there was a snap ring right behind the seal and a step between the two 16002RS bearings. Pressing them out destroyed the step and snap ring. Now I know. TC 15-32-5 seal costs $2.55 so I will stock up when I make a final choice.
A Nema 34 gearbox print. This is the next chassis size up.
Looking forward from what I’ve been learning.
- Finding a larger NEMA 34 gearbox to work with should afford some higher torques and larger gears. The OD of the 23 is 57mm. The 34 is 90mm. That’s a 58% increase.
- Even some of the cheapest gearboxes in the NEMA 23 sizing have needle bearings on the planets. That’s a very good thing.
- There is significant space to save by modifying a gearbox. Removing the flanges brings the with of just the gearing element to 25mm. That could go down to 18mm if I cut some of the ring off. The 34 box will be thicker.
- The BCD of the 23 ring gear is about 4x51mm M4. That will be larger on the 34.
- The quality seems fine for what I expect to do. The cheap gearbox feels very nice.
- These are not lightweight. Most of the initial weight of the unit remains when removing the flanges as those are just aluminum.
- I would like to find a helical gear cut in the next sample.
- I high rigidity planet gear mount with pin support on both sides.
- A completely liquid-tight, IP65-sealed oil bath environment.
As I’m looking at this area, I also modeled a Sur-Ron jackshaft. This was purchased on Amazon for $94.99. There are some cool things about this part. At the least, I have a final drive sprocket now. I don’t know if this will have any value but I have the records of it now.
