Redrock FF Gear Lash

Ted Spencer

Ted Spencer

Veteran
I just received a brand new Redrock Follow Focus today and set it up on my system. It was quite easy to do. However, I noticed immediately that there was a considerable amount of gear lash - both when simply turning the knob/gear in my hands and when fitted to the lens. Measured at the edge of the marking wheel, I see about 3mm of free play between rotational directions.

I should mention that this is only the second time I've used a FF. The other time was an IndiFocus (the updated version), and I don't recall feeling much play at all in the gears.

It's enough on this Redrock unit that critical focus is quite challenging, as there's a long "gap" to be covered between each direction of movement. It's also enough that the mark on the ring is only valid for one direction of movement. A mark made after focusing clockwise is quite inaccurate when focusing counter-clockwise, and vice-versa.

Being pretty inexperienced with these things (but again - seeming to recall that the Indifocus didn't do this), I'm not sure whether to conclude that the unit is not working properly or not.

I have read a great deal of praise for the RR FF, along with comments like "no play" and so forth. I'm certainly not finding that to be the case.

I'll have to wait until after the holiday weekend to do anything about it, but thought I'd post here for now to see if anyone might have some insight on the question.

Thanks!

(This was also posted on the forum at RR's site)
 
No, the RR FF is certainly not 100% without play/lash and it doesn't have the ability for the user to "tighten up" the lashing like the Sgpro and Zacuto's FF. The play is the LEAST of the problem for the RR FF.
 
"No play" is an exaggeration. Every FF out there has play to some degree, 3mm is a tad more than I've noticed on my Redrock, although it's still not a lot. I've used the Chroziel FF and it exhibits about the same amount of play.
 
I used a £2500 arri follow focus and it had about 1.5mm of play. I was shocked, for that price it should wipe your arse for you, let alone work properly.
 
I measured it again, very carefully, and it's more like 2mm. Sill feels like a lot though. I guess I'm surprised that such a simple gearing design (presumably two identical beveled gears mated at a 90 degree angle) should have so much slop. Maybe that's just harder to get rid of than it would seem. Anyway, if my unit it representative of both RR and most of the rest of its pricier competitors then I guess I'm doing ok.

I still have the nagging memory that the IndiFocus was almost zero-play though (I saw it at our DVXUser colleague Kwan's NYC studio a couple months ago). Anyone who owns one of the updated IndiFocus units care to comment on the accuracy of that particular recollection of mine? Kwan?

Thanks for the feedback so far.
 
Dont forget some of the play may be coming from the lens and the FF gear meshing. maybe you coudl push them closer together and check again. Also check that the grub screws that hold the knob and the output gear onto the shaft are done up properly, as that can cause some play too.
 
I have the RRFF and their is a REV gear box they offer. I got one several months back and it solved my play problem.
 
Mine is brand new, just built to order last week, so it would presumably be the updated gearbox, which was implemented quite some time ago. Evidently the earlier version had something like 5mm of play which would seem very excessive.

Have you measured the free play at the edge of the marking ring on yours? on mine it's easily wider than a typically thick dry-erase mark, or about 2mm. It's very obvious on mine when flicking the ring back and forth without the lens gears turning at all.
 
Nylon gears instead of brass maybe? It makes a really big difference.

The Cavision FF and Arri FF have little if any backlash. The Arri (5HD) I used on my last show had zero discernable backlash. My Cavision RFF-15B has none. The new RFF-1560B reportedly has less than the model I have (previous), which I take as a good omen.

e
 
Hmm...I just tried to look at the "buy" page for the FF on RR's site, and it says "this item no longer available". I wonder if I *just* bought a now-discontinued model...

Strange...
 
RR gears might have a tolerance spec. that is +/- 2mm. If so, it possible to take two parts within spec tolerances and have them stack into an unacceptable spec. One gear could be on the edge of -2mm and another could be on the low side -2mm also, together they could equal a 3.9 gap. This is called tolerance stacking, it's common and needs to looked out for. It's what caused American auto engines and such to be inferior to Japanese engines and such of the same design & tolerance spec. The good Japanese producers were able to control variation using process controls and produce nominal spec parts. These parts were precise to the point where practical concerns were unwarranted.

RR needs to be mindful and match gears for min. slop.

This is just one idea as to what is possibly happening. Given the differences from owners of the same product, I'll bet this is the issue at hand. To correct this, one gear needs to be replaced with a unit measuring on the + end of the + /- =spec.
 
To be fair to RR, the total 'slop" is only 2mm. But it feels and looks like a lot to me.

I posted a short clip of it on YouTube. Note that neither the lens gear nor drive gear are turning as I flick the knob back and forth slightly after turning it.

Here's the clip:

http://ca.youtube.com/watch?v=Zp89IsMhUtE

Is that a normal amount of gear lash?

Thanks for your input.
 
Thats not normal. Yours has way more than any other redrock FF I have used. Is it possible that it was the old version? The new one has almost "no play" or its unnoticable.
 
Ted,
Show brian valente that youtube video, assuming you have set up the FF correctly, then your FF is definitely defective.
 
Thanks guys. That's *very* reassuring.

I've carefully checked every setup paramater (of which there are relatively few), and the problem is definitely inside the gearbox itself. The knob and gear are firmly bolted on, the gears are meshing cleanly, it's firmly tightened on the rods, the center setcrew is tight, etc., etc.

I will contact RR tomorrow and make them aware of the situation. Hopefully it's just a matter of replacing the gearbox. Maybe they inadvertently used a pre-updated one.
 
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