Alexa powered through Zephyr sled? Answered.

[Robert Starling SOC]

Going back to the stiffness and rigidity thing, is it true what I heard the top stage of the Zephyr is made of some sort of composite fiber/plastic material or a metal casting instead of being CNC machined?

 

Don't shoot me if I'm mis-informed just wanted to clear it up in my mind.

 

Thanks!

 

Robert

[Dave Tree]

yes, correct. 24v. I was going to buy the Tiffen one but the Tiffen supplier couldn't definitively answer if it would power an alexa... So I got one made up for half the price.

Wolfgang that video is excellent. It shows the Alexa taking power from just one battery...

[Alan Rencher]

Going back to the stiffness and rigidity thing, is it true what I heard the top stage of the Zephyr is made of some sort of composite fiber/plastic material or a metal casting instead of being CNC machined?

 

Don't shoot me if I'm mis-informed just wanted to clear it up in my mind.

 

Thanks!

 

Robert

 

You are correct. It's a composite / plastic materiel.

[Mark Schlicher]

Robert & Alan,

 

Important to clarify here!

 

The outer shell is plastic, but the structural "guts" are all metal. None of the structural parts on the topstage (or bottom spar, for that matter) are plastic. The outer casing is partly cosmetic and partly meant enclose the wiring and anchor the connectors. I disassembled mine once, I don't remember seeing any cast parts, I am certain the dovetail receiver is CNC-machined, I believe all of the other relevant parts are machined also.

 

Dave,

 

It makes sense that one battery could power a stripped Alexa with no powered AKS...it is rated 85W with viewfinder, so if you subtract an estimated 5W for the viewfinder (I'm just guessing) and add back 12W for the HD monitor you are at 92W. So a name-brand battery could (just barely) handle a power-hungry Alexa. Note that the GENERICs are typically rated with lower current-handling capacity: The 95watt-hour GlobalMediaPro battery, for instance, is only rated to 55 watts current draw!

 

As for runtime, IDX rates Powercubes (and the similar E-HL9s) at 88 watt-hours; AB rates HCx at 100watt-hours, so a brand new, 100% capacity HCx or Powercube would each last about one hour with a totally stripped Alexa. Not horrible, but you'll still need a boatload of batteries. Of course, if you wanted to fly it like that, you would also need a 12V Alexa power cable.

[Eric Fletcher S.O.C.]

Few things to consider, I seriously doubt that the Zephyr is wired with 14gauge wire up the post which is appropriate for the current draw. The other thing to consider is that you will seldom have a stripped Alex as your payload, While Mark's estimates are a good start he leaves out the upper accessory plate, lower stability plate, full time cinetape (Everyone tends to forget that most AC's use a Noga arm for the horns) the inevitable iris motor for a BASE configuration which means that for real life production use the Zephyr is the wrong choice. Bottom line is that it's a bad idea to show up to job and be worrying that you only have a few pounds of headroom and then getting a camera that's nowhere near as light as you need it.

[Dave Tree]

"I seriously doubt that the Zephyr is wired with 14gauge wire up the post which is appropriate for the current draw."

Makes you wonder why Tiffen has an Alexa Plus sat on a Zephyr and being demonstrated under power at a demo day, if the Zephyr would just burn out.

 

If the job required a considerable amount of steadicam, then obviously a better rig would be advised and required. However, on the majority of 'real world' 'jobs' I work on, we allocate a recce day where what is required/environment and equipment needed is factored. It is at this point, should a steadicam shot be something that a production wants to throw in the mix... It can be. I haven't turned up on a job not knowing what the day had in store for a considerable amount of time. Again, if that was the case, I wouldn't recommend it. I think this is all common sense isn't it?

 

 

Mark,

Indeed the outer shell is plastic to house the twin video pathways and power, but the guts are all metal. As you say, clarification.

[Alfeo Dixon SOC]

Thanks for some of the comments, others kinda prove my point on getting a definitive answer. At no point am I suggesting this is a solution for everything, it's horses for courses. For a simple shot and set-up, my tests so far have proved strong and sufficient.

I've shot a considerable amount of work for clients that don't require a telepromter or external sound, shots utilising high frame rates. I've factored the additional weight of a RFF, filters and a video sender. So as mentioned, I need to test the additional draw of those items.

I have the Zephyr for my C300 kits and others, but it's nice to know at a push, provided that its LW solution... my Alexa can be flown too, maybe not in your real world, but at least in mine.

 

Your announcing to the forum that the Zephyr can fly an Alexa... like Ron said, this is a printed fact, but I was trying to let anyone else reading your post know that they better think twice about the job they try to book with that rig and Alexa.

 

Sure, its great you own both, but many do not own the camera and will NOT be given a prep day with the AC building the camera to work out the kinks as you have done, but you still do not even have your remote focus motors and MDR/Bartech hooked up and I guess your going to go tethered (another 4.5lbs). If you noticed my F65 post... I spent an entire day at the camera house to work out the kinks and boy there where a few... intact so many that I ended up not being able to test with Cinetape and CamWave mounted due to everyone wanting to go home. If I had just shown up on the day as most productions try to make us do, I would have been in a world of shit storms "figuring it out" on set with an AD look at me like I'm worthless. Sure you can tell them you should have had a prep day... but guess what buddy, your costing them a lot right now!

[RonBaldwin]

My initial response was really a giant "no siht" to this gentleman's wonderful discovery that a 21 lb 24v camera will balance and power up on a rig that is rated for 23 lbs and is wired for 24v. I say DUH.

 

Most likely for what he will be doing he will not need everything plus the kitchen sink on this thing to make it work -- he's the alexa owner who will be controlling the set-up and be working in a small market. If this guy was going to show up in LA/NY and start trying to shoot episodics/features/live tv then I would obviously say that he is high.

 

Is it the right tool for this camera? Probably not. Will it work if you are careful and keep things simple? Yes.

[Eric Fletcher S.O.C.]

"I seriously doubt that the Zephyr is wired with 14gauge wire up the post which is appropriate for the current draw."

Makes you wonder why Tiffen has an Alexa Plus sat on a Zephyr and being demonstrated under power at a demo day, if the Zephyr would just burn out.

 

 

Well all you have to do is check the power plug size (Lemo 0B 303) cross ref the pin diameter (.9mm) and then check lemos chart for wire size and it's guess what... 22ga and that will provide a 16% line loss (roughly 2 volts) when powering an Alexa

 

So yes it's an inappropriate wire size for that camera

[Mark Schlicher]

I don't think any Zephyr owner in their right mind would try to sell their rig as appropriate to a typical NY/LA big-budget/studio/network set. Like any rig, the Zephyr has limits that determine what production environments, what markets, what kinds of clients it is suited for.

 

That said, researching, but not relying exclusively on, published specs makes sense. Tiffen's published Zephyr specs were incomplete and initially inaccurate. Testing confirmed this. The Zephyr is still a new rig (barely a year of actual production units in the field) so there's a lot of experimenting going on, as to what will work and how to make it work.

 

So...thanks Dave, for sharing your experiences and adding to the real-world knowledge base. It sounds to me like you have a good handle on your business model and it sounds like your Zephyr will work well for you and your company.

 

Thanks, all, for your perspectives and cautions. They are important and well-stated.

 

Re: the wiring, I've been told by someone at Tiffen it's 22 AWG. I was also told "22 is fine for the 100 watts of power". Voltage drop appears to be less than one volt. I'm sure 14AWG would be better.

[Eric Fletcher S.O.C.]

.Re: the wiring, I've been told by someone at Tiffen it's 22 AWG. I was also told "22 is fine for the 100 watts of power". Voltage drop appears to be less than one volt. I'm sure 14AWG would be better.

 

 

Math and real world experience says otherwise. 22ga wire is not approximate for 100watts. That's why Tiffen and PRO use larger wire gauges as camera consumption goes up.

[Mark Schlicher]

Quoting what I was told by a Tiffen factory employee. His exact words. He also predicted ".5 to .8V voltage drop" which tracks with my quick observation on a recent Epic gig.

 

When you say "not appropriate" do you mean not ideal/not preferred, or is there a significant potential safety or sudden failure issue?

 

An electrical engineer built an 24" Zephyr/Alexa cable for me out of 18AWG cable, and did some tests on his programmable test rig. At 45 minutes of continuous load at 110W, 27-24V (about 4.2A), the cable rose in temperature about 10 degrees above ambient and leveled off within 15 minutes. At 112V and 12V, the cable rose 45 degrees (to 120F) in 10 minutes, which he described as "uncomfortable" but "still useable".

 

Can't directly extrapolate these results to a 22AWG wire at 48" inside a center post, just reporting the information, since it is often said that 18AWG is also insufficient.

 

I'd like to know more about the math involved. How do you arrive at the 16%/2V loss estimate?

[Eric Fletcher S.O.C.]

Quoting what I was told by a Tiffen factory employee. His exact words. He also predicted ".5 to .8V voltage drop" which tracks with my quick observation on a recent Epic gig.

 

When you say "not appropriate" do you mean not ideal/not preferred, or is there a significant potential safety or sudden failure issue?

 

An electrical engineer built an 24" Zephyr/Alexa cable for me out of 18AWG cable, and did some tests on his programmable test rig. At 45 minutes of continuous load at 110W, 27-24V (about 4.2A), the cable rose in temperature about 10 degrees above ambient and leveled off within 15 minutes. At 112V and 12V, the cable rose 45 degrees (to 120F) in 10 minutes, which he described as "uncomfortable" but "still useable".

 

Can't directly extrapolate these results to a 22AWG wire at 48" inside a center post, just reporting the information, since it is often said that 18AWG is also insufficient.

 

I'd like to know more about the math involved. How do you arrive at the 16%/2V loss estimate?

 

 

You've made a few leaps in your post. the center post cable is coiled and longer than 48", which is actually half of the round trip (48" is really 96"+ round trip) then of course there is skin effect and internal heating which raises inter resistance, oh and don't forget that once you bundle wires their capacity drops in half (Jim Bartel also posted on that)

 

This has been discussed previously on the forum and in the thread Jerry agreed that 22g a wire is not appropriate for high current use. Those post also have links to current capacity calculators.

[Mark Schlicher]

Eric,

 

You've now stated four times that 22ga wire is "not appropriate/inappropriate" with little elaboration beyond "math" and "real-world experience". I understand that this is your considered, informed professional opinion. I'm trying to have a clear view of the data and assumptions underlying your opinion, as well as the type and level of risk of powering an Alexa on this rig (and how to minimize/mitigate it if possible).

 

This discrepancy between your advice and Tiffen's lies at the heart of the topic of the thread.

 

I haven't disassembled my post but I believe I've read that Tiffen sleds use a rubber-band-y thing instead of a coil, reducing the length of cable considerably. That's why I estimated 48" instead of 96".

 

I studied the thread you're referring to at the time it was active. I read about the skin effect and internal resistance and bundling issue. All understood in general. I don't have local access to a test rig to test empirically.

 

You stated a 16% loss based on doing math on 22ga cable. How did you arrive at that specific number? I'm genuinely trying understand what you took into account.

 

Since the Alexa accepts 12-30V, if the sled is offering 28.8 nominal, even two volts of voltage drop is well within what the camera will accept. So voltage drop in itself shouldn't be a problem, right? Heat buildup, possibly, of course. Am I missing something else?

[Eric Fletcher S.O.C.]

Mark search the archives it's already been discussed, and it's not just my opinion, it's that of electrical engineers.

 

The electrical path for voltage drop calks is ROUNDTRIP Out from the negative back to the positive (Electricity travels from low to high) if 22g a is fine for an alexa ask Tiffen why they use 14g a in the U2, why Pro uses 16Ga in the center post, Why XCS uses 14g in the Center Post.

 

Did you go and used the Voltage loss calculator? (Apparently not since you still want to be spoon feed) Go and learn about cascade loss, skin effect and what happens when you have a twisted or bundled wire harness.

 

Yes you can run a camera with a 22ga power run, what you trade though is battery life, short cycling and unexpected shutdowns due to battery droop