Paul C. Buff, Inc. Technical Forum

I'm in the process of charging my unit which I just unwrapped. One question I did not see answered in the Quick Start Guide: The connector end plate has; in addition to two grounded AC outlets, on-off toggle, 30 amp automotive fuse, LED's indicating battery charge status, a 500 mA USB charging port for cell phones, etc., and a charging connector for the supplied AC charger; an earth ground connector that may accept a mini plug. I didn't see an explanation for this in the Guide. Is this to be used to ground the light stand? Or what is its function(s)?

Beyond this, I should say that my initial reaction to the overall design is that it is very well thought-out, including a clamp for attachment to the light stand, shoulder strap, compatibility with a 12 VDC lead-acid battery in place of the lithium ion one, such as through a car battery "cigarette lighter", and a very well-written user guide.

The ground connection will not ground the lightstand, since there is rarely, if ever, any connection on light units between the AC third wire ground and stand mount.

There is also no safety issue or code requirement we have been able to uncover in operating the Vag Mini without an earth ground. The reason I included the grounding point is because I have seen flash units that can get flakey (ie, self tripping, etc) when operated without the normal earth ground provided by a three wire household plug.

One note: While Vag Mini will operate from a car battery, the car charger adaptor supplied with earlier Vagabonds cannot be used to charge the Mini. The Mini's Lithium requires a specific 16.8V charger with different charging characteristics than an SLA battery charger. For this reason, the older Vagabond Car Charger will not plug into the Vag Mini Lithium.

Thanks for the answer, Luap. I was just puzzled by its existence without explanation.

I can report excellent results this morning. I got a shorter power cord from an old computer, hooked everything up and went outside to take some trial shots with an X1600 using the CyberSync transmitter and receiver that just arrived. I can see I'm going to have lots of fun exploring the new creative opportunites this system makes possible.

It's as if I can now carry a tiny piece of the sun anywhere I go; even for IR photos, where xenon emits strongly in NIR. Thank you so much, Luap, for inventing and providing it to us; well worth the wait, by the way.

One additional question, if I may: How robust do you think the plastic clamp is? Do you think I can leave the unit attached while moving the lightstand around, assuming no radical forces are applied? Is it made of something tough like glass-filled nylon, or will it be subject to fatigue? Any embrittlement at cold temperatures?

The clamp and the rest of the VML plastic parts are hi impact strength ABS and should be quite durable, so I think you're OK. I don't have ultra low temperature info.

I generally avoid glass filling these plastics because the result is some increase in absolute tensile strength at the cost of a huge reduction in impact strength. In layman's terms this mean a glass filled part will be stronger if you put it in a vice and squeeze it, but it will crack and break much more easily if you tap it with a hammer.

The biggest issue with any plastic is how well the molder follows the proper molding temperatures and pre drying the material before molding. We see occasional examples, both from our US and China molders, where ultra strong Lexan parts have broken easily because they weren't molded properly. That's one reason we chose ABS for these parts . . . because ABS is less prone to these molder errors.

Thanks. I've been a technologist in plastics and materials for over 30 years, and while I think your plastics education is somewhat lacking, I'm glad to know what the bracket is made of. I'll treat it carefully and will not proceed with my planned 15 second repetitive drop test from one meter on a concrete floor to see how many cycles it will sustain before failure. ;)

My plastics education does have limitations. What material do you suggest, and why?

I'll be frank. While I think the design of the VLM is excellent, the achilles' heel is the stand clamp, in my opinion. Perhaps you could share the thinking that went into this spring-supported clamp design. I'm not sure what the function of the spring is.

Materials wise, your comments about "glass reinforced" plastics would be true for thermosets, such as typical, cured "fiberglass" plastics. These are brittle composites, great for high temperature applications where creep must be minimized. But you can't beat glass reinforced nylon, in my opinion, for an application such as this. It may be overkill here, but I would like to know for sure that my investment isn't going to hit the pavement, (especially not every 15 seconds ;-) But seriously, I think the cost differential of ABS vs Nylon in this application would be pennies, and it would afford the owner a a higher level of assurance.

Getting back to the original question, what the heck is going on with that clamp design and spring? I don't get it.

The spring allows quick release of the clamp. If more tightening pressure is desired, the spring can be replaced with a suitable length of 1/4" ID tubing. On some tubing sizes, the knob can be tightened such that the spring can be fully compressed, coil to coil to simulate a rigid tube.

The design intent is to hang the VML on a lightstand section with the bottom of the VML resting on a stand knuckle.

Some users have applied a piece of adhesive backed friction material . . . such as rubber, and found the clamp will support the VLM on the stand without it needing to rest on a stand knuckle.

Your points on glass filled Nylon may or may not be valid. There is no question that glass filled injection molded parts have near-zero elongation before break and and poor notched IZOD impact strength than virgin materials. I have seen plenty of glass filled Nylon lightstand parts crack and break when tightened.

We have recently hired a highly experienced plastic molding engineer with an MS degree and 40 years experience and I have posed the question to him.

I can say that I have tested virgin Polycarbonate AB and Einstein housings by tossing them approximately 50' in the air and letting them land on concrete, with no breaks or cracks. On the other hand, we have received similar parts that were not dried properly or molded at the right temperatures and experienced failures. Failures are eliminated after we demand closer attention to molding machine parameters.

I figured that was the case, that or attaching it to one of the extended legs of the stand. I'm actually more comfortable with the latter. The idea of using an adhesive backed material on the vertical shaft of the stand hadn't occurred to me, and this may well be the best solution.



All of the above is good news. My experience has been primarily in thermosets, and I would quickly defer to your direct experience and the views of your plastics expert with respect to the thermoplastics you've used. And I apologize for my previous flippant comment about your education in plastics being deficient. But then I guess we might all admit that no matter what we know, we may also still have something to learn.

I still think the light stand clamp design is not well thought out, though. If an additional brass insert had been incorporated on the other side of the case with the bracket extending to both, I would have liked that design much better. Allow me my opinion here, at least.

This is a minor point, however, because overall this VML device is an incredible advance and one which offers such a wide range of possibilities heretofore impossible, that a work-around clamp issue is no big deal.

Again, thanks to you and your organization for making it available.

I'm not saying I'm right, and admit to having less plastics knowledge than many. There are arguments for and against the tradeoffs between absolute tensile strength and impact strength and elongation before break. The latter issues are extremely effected by the part design, particular in the avoidance of sharp corners that form high stress points by using generous radii.

The biggest fault-inducing factor I have seen, from both US and Asian molders, is improper material drying and molding temperatures. As stated, this can turn expensive ultra tough Lexan into soda crackers. This is one reason I chose high impact fire resistant ABS for this application . . . it is more forgiving of molder mistakes than Lexan (Polycarbonate), which places high demands on the molder.

I never take any offense to valid comments and suggestions such as yours. But in the real world, with 2 month+ lead times and millions of dollars of already-made components, "could have/should have" suggestions are generally impractical to implement in any reasonable time frame and usually end up as considerations for future iterations.