Paul C. Buff, Inc. Technical Forum

I sometimes have a hard time mounting large softboxes to my Alien Bees. The two softboxes I have difficulty with are a Photoflex 84" Octadome and a Photoflex 4'x6' softbox. I use the PCB speedring with each of these softboxes but the weight of each creates quite a bit of torque on the speedring. In one case, the aluminum mounting plate on the speedring bent and the octadome came off. Even in the best of circumstances, the "fingers" on the monolight seem to strain to keep these large softboxes in place. Can anyone offer any insight or advice?

Tim

Our lights are designed to withstand 25 foot-pounds of overhung torque weight. While the boxes may not be that hevy, thier extension from the light, combined with the weight could be too much for the lights.

Thanks, TS. Here's the math on the octadome - it weighs less than three pounds and its depth is less than three feet (although the spec claims two feet). These numbers yield a torque of 9 ft-lbs. The prongs on the monolights seem to strain under this load and can deform the aluminum mating ring on the speedring. The prongs serve as a stress concentrator on the ring. All of this may be "as designed" - if so then it's all good. Also, I'm curious to know if the Einstein will have a similar design - i.e. prong size, spring constant.

Tim

I appologize. Being a car nut I think in pound feet, the torque rating is 25 pound inches. Doing the math the same way you did, you have 108 pound inches (this is actually high, as some of the weight is closer, thus applying less torque).

Einstein will accept the same accessories, however, the mechanical design is different. I do not yet know if the load rating is different or by how much.

I've always been curious whether the Balcar mount was sturdy enough for large modifiers.
I usually hang a speedo beauty dish and grid off a white lightning instead of an AB, so Tim if you can find someone local who has a WL, you might want to see if that's better...

Tim, I use Photoflex 3x4 ft. softboxes and speedrings on my WLs and the mounting fingers on those lights are more robust and hold better. Seeing as how you are using a much larger and heavier softbox on AB lights, I would mount the speedring right onto the light stand. Photoflex speedrings have the ability to be mounted right onto the stand giving better balance between light and softbox(not sure if PCB speedrings can do this). Of course you would need an umbrella adapter(swivel bracket) to go between the two. I've used this configuration with good results and good balance with large to XL and heavy modifiers.

RMS

Thanks, guys. That's all really helpful information.

Tim

Asking the obvious question... if the speedring is mounted to the light stand, then the weight of the strobe is on the mount instead of the weight of the softbox. Will all the AB's etc support their own torque-weight when suspended from a stand-mounted speedring?

You should be OK with Alien Bees and Zeus, though i would be reluctant to do this with White Lightning lights, more so as the size increases. We have not test this, so i cannot make any gurantees.