Hello truck builders and anyone else that can help.
Can anyone tell me what this is and what it's for?
The location is between the gear box and in front of the transmission on an old Mack truck chassis.
description: double chainring sprockets with chain looped around them that connect to nothing else.



This is a link to the build I'm doing of this vehicle, with a picture of the whole vehicle. http://scratch.kitmaker.net/forums/96993#802182

This vehicle is an old military display piece. I'm thinking that it was stuck in there for display assembly purposes but I don't know.

Thanks for looking.

I'm not that of a mechanic, but it looks like a "homemade" flywheel of some sort.

Having been a mack driver in the army i thought i my be able to help, but then i followed you link and was totally lost.
Try following this link and emailing the guys in parts, i know it's a long shot but it's worth a try:

http://www.macktrucks.com.au/index.cfm?MenuID=101

It's Possible... it's a PTO....... (Power take off) that in this case wasn;t used for a Winch or something else.

Since it was chain drive, I go along with another chain drive power take off that wasn't or isn't being used. No telling what the original chassis was used or designed for.

Thanks for your replies guys.
I didn't think of those options before.
well, the build continues...

It's a universal coupling...done in chain, between two close proximity sprockets. It gives alittle torque wise and twist/flex wise. We had that setup on one of our old toggle headers. There should be a removable link on that chain for service/part removal. Modern equivalant would be a CV joint or pin type plates with a captured flex element{polymer} in between.

Thanks!
I still do not understand how it works, but now I'll include it. I almost wasn't going to.

It's a "flexible" joint in the drivetrain........ you have 2 sprockets near each other...... and the chain that wraps around them connects them while still having a bit of flex to it.

These are great replies, thank you.
But I still don't get it because there are two sprockets and two chains. Each chain is wrapped around it's own sprocket.

oh... wait a minute...

This is one chain, that looks like two chains side by side, and the sprockets are independant?
Now I'm seeing the middle liniear link between them. I didn't even notice that while taking the picture.

Thanks Bob,
Interesting, as I work with Flexible couplings all the time. Never did see one of these though. Guess my antique plant isn't that antique afterall.

Dave, we had a 1916 vintage 3/4" waterburry toggle solid work header with that connection on it...the flywheel was almost as tall as me{I'm 6'4"}. The quad A belt drive bearing assy was joined to the motor with such a double chain...beefy sucker!...and you want to talk about thumping when she made a part!.......

this is where it is now



thanks for all the replies and help!