On the other hand, the actual motors have an arrow on them indicating only CCW (as viewed from the sprocket) operation. I also recall a motor repair guy many years ago telling me that compound motors should not be run in reverse (no reason given). So, I figured I would consult the collective wisdom of this list before doing anything potentially dramatic.
Just back in from checking the posts and polarity. My recollection was that there are no markings on the posts, which is true. (On series motors they are usually marked A1, A2, S1 & S2). On one compound motor I had years ago, they were marked A1, A2, S1, S2, F1 & F2 - but posts F1 & F2 were smaller which indicated they were the shunt field.)
I misremembered the posts on this motor. There are 5, not 6, and they are all the same size. There are only 2 power connections to the motor, but there are jumpers across two pairs of posts. Some ASCII art below (use a fixed width font). Think of this as a 'Top View' where bottom is defined by the base plate.
(Negative (Positive
Connection) Connection)
Post1 Post2 Post3
============ Jumper
___________________________________________________
| |
| |
| |
* | Motor body |
Shaft *==| (base below - not visible |
and * | |
Sprocket | |
| |
| |
___________________________________________________
============ Jumper
Post5 Post4
(No external
connections)
(In hopes of providing some clarity in further discussion, I have
arbitrarily numbered the 5 posts CW from top left, but there are no
markings on the motor itself around the posts.) The jumpers are fairly
thin metal, which suggests to me they aren't intended to carry as much
current as the main power wires, but that's just a guess.
I have never taken one of these apart, but commutator and brushes (armature power) is usually at the external shaft end (no tail shaft on this motor), right?
So, with only one connector post at the shaft end of the motor, which are the armature connectors?
Darryl On 9/5/2019 2:22 PM, RJ Kanary via Elec-trak wrote:
Not authoritative, but a start......... https://www.quora.com/How-can-the-direction-or-rotation-of-a-DC-compound-motor-be-reversed RJ Wishing his Dad was still alive to answer that question. On 9/5/2019 1:35 PM, Darryl McMahon wrote:I have been using a spare ET snowthrower motor over the summer to power some test rig contraptions over the summer, and it's worked like a charm.Last week, I was asked to try powering something new (possible amphibious drive 'tire'), but the new wrinkle is they want to be able to move forward and reverse.As I understand it, the snowthrower motors are compound wound - strongly series but with a weak shunt field to prevent motor speed runaway. On the blowers and tillers, there are jumpers between what I expect are the 2 sets of field windings. (I don't have a schematic for these motors.) Which posts do what on these motors (there are six external connection posts). For ET use, only two connections are used (pack positive and pack negative).On a series motor, this can be done by reversing the field or armature connections (but not both).I'm looking for guidance on the possibility of reversing one of these motors. If that's doable and not going to damage the motor, I expect I would be putting a set of contactors in place to be able to do this conveniently and repeatedly. I need the motor to survive so it can go back on a snowthrower in a couple of months.Thanks in advance for any documentation or guidance, Darryl_______________________________________________ Elec-trak mailing list Elec-trak cosmos phy tufts edu https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak
-- Darryl McMahon Freelance Project Manager (sustainable systems)