I hope its easier to understand now with the parts in place
I know the shift-piston is not attached, but its in position
the bosch still needs to be geared down to 4:1 before its torque is transmited to the diff, but at least its in position
the long black shaft is the output
Tytus,
The problems I see are really problems of preference.
That leaves your output sprocket as a hanging rotating moment. Whether that could really be a major problem can only be seen with testing. Which I am sure you will do.
Remember, these are not insults, nor are they facts. You have not given us any measurements, only angled views. Without at least an orthographic view, it’s hard to estimate the spacing and clearence. I am not saying this gearbox will not work. It is very possible, in fact, very likely that it can work. Those 2 points are MY views by what I can see. Yes, I understand you would want a small sprocket on the output for further reduction at the wheel, but how small is efficiant?
There’s my critique, nice work Tytus. Both in idea and modeling.
Gimmie a break, All i got is 3DS-MAX
*Originally posted by Tytus Gerrish *
**Gimmie a break, All i got is 3DS-MAX **
Tytus… don’t take it too personally. Brandon specifically said that. It’s just a critique, not slamming your design or design methods. It WOULD help if you could do some more technical layouts, say in Inventor or some other modeling program.
hay, i know Brandons just Messing around with me. He loves to give me a hard time, hees been dissing me since febuary , But i know He loves me;) Right Brandon?
Yay a differencial. My only beef with the design is that its quite large. I rough guessimate of size puts it at nearly a foot across. I’d reccomend placing the motors on the same size and squishing everythig together.
I think its looks fine (especailly the urban camo for the casing)
My 2cents.
What if you put bevel gears on the input shafts outside the box and angled the motors back 90 degrees? That would make it more streamline, more compact, and leave room for chains to get to wheels, although it adds more components.
Then i would be catching flack about how much more innefficent i made it, a bevel is like 70% efficent and a straight coupling is juct under 100%
Its a lot Whider than it would be in reality its realy just for the viewers advantage all the parts are Big and easy to see
How are 2 bevel gears making contact 70% efficient? If you’re concerned with efficiency, put spiral bevel gears on them, or use 2 helical gears and mounbt them perpendicular to each other. The point I was trying to make was that it would pack better if the motors were angled back instead of sticking out.
Tytus, first of all, I don’t feel I was ‘dissing’ you at all. I’ve said many times that it is a good design.
As to anthony towne’s idea of “streamlining with bevel gears”, it would add more compononents, yes, but it would also add a considerable amount of weight.
If a team decides to build this to specs Tytus provides (assuming he will if this works), and they 90º input was also used, there is more to it.
An angled mounting plate which would be free hanging on both sides. This would have to be at least larger than the diameter of the chiaphua (which I think was 2 1/2"). This would bring in the design probably about 5 or 6".
Also, as Tytus said, it would be less efficiant. I’m not sure if bevels are 70%, I thought they were roughly 95%, but either way More Gears = More Weight & Less Efficiant.
Angles from helicals would also change the way the mounting plates are in.
Personally, I see more harm than good in adding angles
Sorry, the design does have a fatal flaw. The higher torque motor will overpower the lower torque motor.
I am not sure why all the concern of matching motor speeds. Just gear the two motors to output the approximate same speed and both will contribute very nicely.
Though I’m not sure of the net effect of “overpowering” another motor, as Bill Beatty suggested, he is correct in pointing out that a differential is not ideally suited to matching the output speeds of motors. Open gearing is simpler and more efficient, due to the fact that the performance of both electric motors is effectively linear, there is no need to accomodate different relative speeds–the gear ratio necessary to match the speeds of two different motors is just about the same at any given final output speed. If, for some reason, you were varying the input to the motors independently, then maybe this could be useful–but why would you do this? It would mean that at least one motor is not operating in the optimal state for a given situation! (It would be spinning faster or slower than it needed to be, and the differential would be matching the speed.)
The differential adds complexity, requires very high manufacturing tolerances, not to mention significant custom machining. It is large and heavy, and, with the size of the gearbox approaching 16", by my estimation, measures need to be taken to reduce its size and weight.
And a couple of other things:
the urban camo for the casing
That looks like an approximation of galvanized metal, which probably would not be used in such an application–there’s no real need to prevent rust!
The drill motor that Tytus Gerrish has used is not the Bosch 3360 from last year, but instead appears to be a scaled-up version of the older Bosch drill, used in 2002 and earlier. (You can tell by inspecting the shape of the rear housing–the 3360 has an exposed rear section, with the contacts on the sides, instead of the fully shielded rear section.) I say scaled-up, because in the drawing, it appears to be of similar size to the Chiaphua (or did we decide that we’d all call them CIMs?), which is certainly not accurate.
-Tristan Lall
With the two motors of approximately the same horsepower but with no load speeds of almost 4 to 1, as the load increases, the CIM motor will actually stall out the drill motor and then drive it backwards! I would call that overpowering the drill motor…
I see no benefit in adding the complexity of a diiferential to this system. Just gear the drill motor down approx 4:1 and have both drive the input shaft. It will work just fine.
There was a team in Chicago two years ago that was displaying what they called an “infinately variable transmission”. It used a differential on the input, and the idea was, when the load was light, both motors would contribute to the speed of the robot. An interesting idea. They had to go to a worm drive input on the higher speed motor to keep the system from backdriving it under load. They did not need a clutch or the two speed gearing.
*Originally posted by Tristan Lall *
** That looks like an approximation of galvanized metal, which probably would not be used in such an application–there’s no real need to prevent rust!
The drill motor that Tytus Gerrish has used is not the Bosch 3360 from last year, but instead appears to be a scaled-up version of the older Bosch drill, used in 2002 and earlier -Tristan Lall **
“First make it work then worry about what it looks like” Galvanized tubes PVC tubes aluminum tubes, so what? its just a spacer
its an old scaled up bosh because i cant find a model of the new one or its transmission
This drawing is just to demonstrate how it would come together, its comparable to a stick figure instead of a Mona-Lisa don’t take the size literary.
I’m just trying to share my ideas I hought that was what CD was about. So what if it doesn’t look perfect, Gimme a break
as for the mechanical end of things heres my experiment…
Rig this gearbox up with a CIM and a bosch,
rig a “Run-of-the-mill” spur merger gearbox with a CIM, and a bosch,
connect the output shafts to Other motors to use them as generators and use mulit-meters on the generators to measure Watts
when you apply power to the motors in the transmission measure the watts you put in, and the watts you get out with a load of Resistance on the generators and record the difference in the watts applied and the watts generated (DYNO TEST)
the arcs of the watts will tell you the story of efficiency
remember… 746Watts=1HorsePower
Originally posted by Bill Beatty
With the two motors of approximately the same horsepower but with no load speeds of almost 4 to 1
Originally posted by Tytus Gerrish (in the caption from this picture)
the bosch still needs to be geared down to 4:1 before its torque is transmited to the diff, but at least its in position
From the caption of the picture, Tytus alluded to gearing down the Bosch by a further 4:1. This is why I wasn’t sure what was meant by overpowering–the speeds are already matched, though he hasn’t drawn this in yet. This is also why I believe the differential to be redundant–the motors should be sufficiently synchronized without having to resort to a differential assembly.
-Tristan Lall
Tristan
I missed the 4:1 gearing of the drill motor. I agree, the differential is unnecessary.
I am wondering how the team (I don’t know their number) that built the transmission I saw in Chicago is doing. I am not sure I agree with the design, but the workmanship was superb. Anyone out there who can bring us up to date with some info?
*Originally posted by Bill Beatty *
**I am wondering how the team (I don’t know their number) that built the transmission I saw in Chicago is doing. I am not sure I agree with the design, but the workmanship was superb. Anyone out there who can bring us up to date with some info? **
From your earlier post, that sounds like Team 217, The Thunderchickens. Mentored by the current UFH Paul Copioli. They called it the CCT (Crazy Chicken Transmission)
By the by, Paul made a white paper for 217’s 2002 version.
I sent a private message to Tytus, if he wishes to share it with the group I have no objections. Basically, I agree will Mr. Beatty regarding the differential. It is unnecessary in this design. Remember that the differential is meant to allow torque transfer to 2 axles from one input and also allowing the axles to travel at different rotating speeds. Its major design limitation is that it will transfer torque to the path of least resistance (one tire on pavement and one tire on snow… snow wins and car goes nowhere).
There are other uses for a differential (redundancy in helicoptors, etc.), but speed matching is not one of them.
Regarding the CCT , it uses a planetary gearset with one motor coupled to the input (sun) gear and one to the ring gear. When selected correctly, you can get a very wide speed range with the SAME output torque. We had a worm gear because we cheated on our gear selection to get more speed. The result was backdriving of the ring gear. If we had used a different gear ratio, the back driving would not have occured (we have experiments to prove it), but we decided we needed the speed.
It took a sacrifice of 2 regionals (Chicago included) to get it right, but we all thought it was worth it. It was working by the 2002 Nationals (ask team 27 … sorry Kyle, I had to add that). We have our patent application in and our pending approval from the U.S. patent office.
If you need further details regarding the CCT, please look in the whitepapers section.
-Paul
Its major design limitation is that it will transfer torque to the path of least resistance (one tire on pavement and one tire on snow… snow wins and car goes nowhere).
Why not use another differnential design that goes around that limitation? That may work backwards insteand of a regular differntial.