Convert, Sprague Clutch

[n3303j]

Reading about the Convert torque converter on Bender's site.
Thinking about reduced engine braking on the Convert.

Then Bender mentions that the torque converter has a Sprague Clutch on the output that drives when input RPM exceeds output but releases when the converter RPM drops below that of the transmission input.

That would result in no engine braking available, and the ability to run at engone idle while coming down the back side of the mountain at 60 mph. Makes for quiet coasting and more involvement with the brakes. Easier to replace brake pads than Clutch disks.

Sort of a revival of the old Saab 93 that was also freewheeling when off the throttle.

[Antietam Classic Cycle]

In my experience, there is some engine braking, more in Low range than High of course. Converts with the stamped flywheel have slightly more than those with the heavier machined flywheel.

[bigbikerrick]

I agree, on the engine braking. You can feel it alot more in low range,when you let off the throttle.  It also helps to be in low range if you try to "bump start" the bike.
Rick D.

[n3303j]

This is quoted from Bender's site:

"Those oval rollers are called sprags. They are used in a lot of auto applications too, and I bet in other power transmission systems. They allow torque to be transmitted in only one direction, i.e. clockwise or counterclockwise, but not in both directions. In the other opposite non-driving direction the two shafts slip without torque being transferred (free-wheels)."

So I'm wondering if the converter connection is truly a Sprague as described above or if the connection locks up above a certain engine RPM and remains locked until engine RPM drops to a certain point. Or maybe the connection locks at a certain speed difference between the two rotors in the converter.

If you chop the throttle on a Convert doing 60 will the engine drop to idle long before the bike slows to 30?

[bigbikerrick]

On my Converts I have found that if you chop the throttle at 60, the fluid drive continues to rotate the engine, although there is quite a bit of slippage. More so in low range.  If you cut the ignition when going 60, then flip the kill switch back on, the bike will restart, as long as you are still coasting above around 40 mph in high range. Slower than that, and there is just slippage, with the engine not "bump starting", unless you are in low range, where it will restart down to about 30 mph.
I tried this experiment to try and determine how hard it would be to "bump start" a convert with a weak battery. 
Rick.

[Bulldog9]

Engine braking on a Convert?!?!?  Bahahaaaaa...... Yes, as some have mentioned in low gear, but any thought of a comparable 2nd-3rd gear engine braking from a 'conventional' transmission in the twisties needs to be abandoned.

[n3303j]

Rick answered my question about the comments I read on Bender's site. The Convert does not have a Sprague type connection in the drive train. There is some engine braking and enough energy transfer when coasting that the engine would actually restart if one momentarily shut off the ignition, then turned it back on at 50 or so mph. You could not engine idle down the back side of a mountain while coasting at 60 mph.