Universal Rotor Log
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Aaron Makaruk - aaronmakaruk@gmail.com
Joshua(JB) - "LoadTest"
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October 16, 2012
LoadTest Posted a 2 part video response to the problem statement video filmed at FeF "Quick Attach Plate and Universal Rotor". The first part is an overview of the design considerations. The 2nd part poses the first design decision and that is to eliminate the auxiliary shaft bearing support structure from the design and rely instead on the hydraulic motor's internal bearings to support the system, with the option of adding in an extra bearing support system only when a hydraulic motor with inadequate bearings is to be used. LoadTest requests Aaron and Marcin to watch the response videos and confer with the decision before he continues further design work. Part 1: [1] Part 2: [2]
October 9, 2012
I'm out all day this week until Friday. I'll try to throw a video together with some ideas. I think the first step is to get Marcin to confirm his decision & the reason for it, which i wrote about on the Wiki, about using the extra shaft and bearings even though they aren't needed. I want to be sure he understands that the bearings in the wheel motors like you are using in the lifetrac now are stronger then the old motors he was using which weren't wheel motors. The old motors couldn't support the weight of LifeTrac, the new ones can depending on which model they are. If it was up to me, i would say don't use the extra shaft and bearings for LOTs of reasons. Especially considering building a Hydraulic Motor from scratch is to be part of the GVCS 50 so it can be made to whatever specifications needed.
Here is the decision as i posted on the wiki: http://opensourceecology.org/wiki/Universal_Rotor
1) Wheel Motors(bearings built in) or Jack Shaft(with auxiliary bearing support structure)?
Due to the wide range of applications, the UR needs to handle high axial and radial forces. Wheel motors have larger bearings then standard hydraulic motors to resist these much higher forces. Wheel motors are available commercially that will handle the radial and axial loads of all current GVCS applications. However wheel motors are low speed. High speed motors don't usually have such large bearings. While generally you don't need large bearings while doing high speed operations, an accident, such as hitting a tree stump with a high speed mower blade may damage a motor with smaller bearings. Adding a separate shaft(jack shaft) that is supported by separate bearings between the motor shaft and tool effectively isolates the motor shaft and bearings from any radial forces, as well as axial forces if properly designed. This is the design currently being used on LifeTrac III and the MultiAuger. The current design on the LifeTrac is excessive in length and has some proven and suspected issues. A much shorter and simpler jack shaft setup should be possible that is more comparable to a wheel motor in size. If a jack shaft setup is chosen as the primary UR setup, it should be designed so that only wheel motor can be used instead with minimal variation(or none) for replicators who choose to do so.
The current quick connect wheel assembly with the jack shaft and auxilary bearings was a necessary component when the LifeTrac was powered by the original weaker drive motors. However during the redesign, new 15,000 Inch Pound Motors were purchased which are actually wheel motors that have a much higher carrying capicity which means the whole jack shaft assembly might not even be necessary as the motor is designed to handle up to 11,000 of radial load per the specs provided by the manufacturer. It has already been proposed by Marcin that the wheel connect be redesigned to address several issues, but in reality, it can actually be completely ommited without having to purchase additional motors.
Comparison: Wheel Motor UR Advantages: -Much more compact, lightweight, cheaper and very quick to build -Sealed & lubricated bearings -Industry Proven -Less parts to break or wear out
Auxiliary Bearing UR Advantages: -Can remove the motor with out disconnecting the tool(or the tire when used as wheel drive) -More motor choices (especially rpm) -Can use a gear reduction or multiple motors much easier
Thanks,
JB
October 8, 2012
- Universal Rotor Log page created
October 5, 2012
- JB annotated an image from the Universal Rotor wiki page.
- I'm missing something. So why not just a single square tube receiver that an implement/attachment with a square tube mount can slide into? Then you pull it out, rotate it 90 and stick it back in (I.E. mower to trencher). Just like on a trailer hitch, just bigger tube, and don't reverse it. Make the receiver the outer tube. And make it so you can add any style adapter in there you might need: extension tubes, right angle tubes, swivel tubes, adjustable angle tubes.