Automatic Clutch types

[Ricks]

As I have been rebuilding 2 auto clutches for projects, one being a single track and the other a double track, I thought I would post a few pictures of each. I have also identified 4 different variations of auto clutches used on the 2 wheel bikes, and a different one used on the late model trucks.  This is not including the Salisbury unit used on a few of the earliest automatic trucks.

Picture #1:  An overview of the 2 I am working on.  Since track on left, double on right. Notice the 2 retaining rings on the double track. These are not used on the single track and I have had the pulley walk out on a single track clutch, so it seems this was a necessary improvement.

#2-4  Notice the difference in the drive pulley. The single track uses bearings while the double uses a bushing.  I feel this was an attempt to save money and a downgrade.

#5-6  Back side of drive pulleys.  Single track used a bolt-on steel plate whereas double was cast into pulley.

#7-8  Early vs late style idler.  Not sure reason for change, they both work equally well.

[Ricks]

Picture #1-2  Single track weights.  This is where I have identified a change.  I had an earlier single track where the weights were made up of 3 parts each, that could roll independant of each other.  I'm sure the change was made for cost savings.  Much easier to machine 1 piece of bar stock than to make 3 pieces and assemble them.

#3  double track weights

#4-5 single track measurements

#6-7 double track measurements

[Ricks]

If you have been following along, I said 4 types and have shown pictures of 2.  The 3rd is the single track with the 3 piece weight system.

The 4th type is on my 1954 rat bike.  I believe these were built for a short time when Simplex was transitioning from the single to double track clutch.  It consists of mostly single track parts, including the drive pulley with bearing, but uses a double track weight system.  Now, some of you are thinking maybe it was just 2 different clutches assembled into 1?  Well, if you look at the measurement photos above, you will see this is impossible due to the length of the bearing housings on the clutch drums.

Now, for the 3 wheel trucks,  a clutch was built that uses 2 sets of single track weights.  Instead of just having the weights opposite each other, they had them on a four sides.  This was to hold the much heavier trucks in low gear longer.

If anyone has a picture of this truck clutch available, please post it here.  Also, if anyone has seen a different type, please feel free to add it here.

[ndian22]

Great job of documentation on the clutch types Rick. Extra effort on your part for certain & an aid to anyone trying to sort out variations. Rick C.

[kartjockey]

Thanks for this post. Being a rocker clutch guy I have a lot to learn.