This Power Test tech tip will give you an overview on dynamometer mounted resilient couplings.  The primary purpose of resilient couplings is to dampen high-amplitude torsional impulses or “torque spikes” associated with testing a comparatively small engine on a large capacity dynamometer.  As a secondary purpose, the coupling provides a drive shaft connection point to the dyno.

When operated as a flexible connection or unlock, couplings maximum torque value is 2,500 Lb. Ft. If you “lock” the coupling by installing the lock-up bolts the dampening capabilities of the coupling are removed and engines can now be tested up to the full capability of the dynamometer without changing couplings. If you still experience torsional vibrations with the coupling locked, Power Test does also offer a wide variety of “engine mount” torsional resilient couplings.

So when testing your smaller engines, you can use the dyno mounted coupling and then you can lock the dyno mounted coupling and install an engine mounted coupling. Allowing one dyno to test many different engine sizes.

Alright, so let’s take a look at the dyno mounted resilient coupling and talk about the adjustments you can make. There are twelve neoprene rubber blocks separating the inner hub from the outer housing. By removing these blocks in pairs, you can reduce the couplings maximum torque value to fine tune the coupling to match your test engine.  Please follow the recommendations outlined when reducing the couplings maximum torque value.

Next I would like to go over coupling maintenance. The following maintenance items are only necessary when using the coupling in the “unlocked” state. When the coupling is locked to the dyno shaft the internal wear components are not in use, so the frequency of following checks will depend on your local usage and conditions.

At the factory coupling are lubricated with NLGI #2 mineral oil grease. There are four grease fittings installed on the back side of the coupling. It is good practice to re-lubricate the coupling with a couple pumps of equivalent grease every 6 to 7 engines of “unlocked” usage.

The couplings internal rubber blocks and brass wear rings should be inspected after 3 months of continued “unlocked” usage. To inspect, ensure the drive shaft has been disconnected and the lockup bolts are removed from the coupling. Start the inspection by removing the outer bolts that secure the couplings drive and end plates to the outer housing. Once the front drive plate has been removed, you can remove and inspect the rubber blocks for flat spots, cracks or other wear. As blocks are removed the outer housing will loosen and can also be removed.

Clean the old grease off the inner hub and brass wear rings. Ensure wear ring hardware is secure and not broken.  Then place the drive and end plates back onto the inner hub, checking for excessive. Brass wear rings provide a renewable bearing surface for the coupling when operated as a flexible connection. If any of the wear items require replacement, Power Test can provide a coupling rebuild kit, please contact us for more information.

Before re-assembly, clean up all the old grease and then liberally lubricate all surfaces and the rubber blocks as you re-assemble the coupling using an equivalent grease.

Well that wraps up this month’s tech tip on the dyno mounted resilient coupling. As always, if you have any additional question please don’t hesitate to contact us for more information.