Please help with CAD design

[anthony113]

Hi, I have virtually no CAD experience and I was wondering if someone who did could design something similar to this: http://www.jbkcine.com/KITA1.JPG for me please. Basically what this is is a follow focus system that would fit onto rods attached to a DVX100 camcorder. turning the black knob causes the little white gear to turn by a belt connected to the brass pulley thing. the little silver thing under the brass pulley lets the "arm" stay clamped in a certain position. heres a pic of it on the camera: http://www.jbkcine.com/dvx100packag.JPG any help is much appreciated thanks!

[Max Lobovsky]

I'm sure there are people on ChiefDelphi that could help you in some way, but as a pretty experienced CADer myself, I can tell you that no one will be able to make drawing from just those two pictures. A large part of the mechanism is hidden from view and there are no dimensions.

Maybe it would be better to start by telling us what you plan to do with this drawing? Is there a reason you cannot by the part yourself? Please give us some more information.

[Elgin Clock]

Originally Posted by maxlobovsky

I can tell you that no one will be able to make drawing from just those two pictures.

Ooh, that sounds like a challenge.... Hmmm....

But seriously, a little more info would be needed. Anyone who knows CAD can model this but it would probably be way off scale, unless you have more info.

Usually, if I am going to model a part to mate to an existing part or mechanism, I use what is called "reverse engineering" and dissasemble the actual part and measure each individual component, model them all in CAD, and then assemble them in CAD.

I had to do this once at a place I used to work , and it came out pretty good... It worked and moved the right way, on the 3D CAD system. That's always a good sign.

[sanddrag]

Originally Posted by Elgin Clock

Ooh, that sounds like a challenge.... Hmmm....

Perhaps we can make a new CD game of this. Post a pic, make it in CAD. Winner is best model before x number of days.

Anyway, if there's a way you can get your hands on a copy of Inventor, you will pic it up very fast and tons of people on here will be able to help you with questions about the software.

[anthony113]

unfortunately i cant get my hands on this part. believe it or not, it costs $1300. im trying to make one for much less. basically the thing interfaces with a gear on the camera to turn the focus ring. im trying to find out measurements and numbers of gear teeth from people on another forum.

[Greg Needel]

part 1


btw just from a machineing aspect it will be very difficut to make that alum ring gear even if you have a cnc mill at your disposal....check McMaster and granger for similar items...also if i am understanding this assembly you are just looking for a fine focus knob. if that is the case duplicating this exactly is not nessicery. you can make modifications to the design as long as it does the same job...for example small parts makes a nice small 90deg gear box that is like an inch long and really light so transfering the power from 1 motion to another might be easyer with something like that instead of building one from scratch

[Gary Dillard]

Here's my thought for a simple (possibly) redesign that may work:

The only critical dimensions you need are the diameter where the ring gear mounts, diameter of the pins that hold it in place (looks like 3 places equally spaced) and the distance from the slide rods to the center of the lens / ring gear.

Buy a stock gear (aluminum probably for strength and weight) that's slightly larger than the camera diameter - scale it from the picture. Bore out the hub to the mount diameter and add the pin holes. This will give you a gear on the camera similar to your picture.

Buy a stock gear that's about the same size as the picture or smaller (can't tell what gear reduction is in the housing), same pitch as the ring gear you bought. This gear will mount on a shaft on an "L" bracket that sits above or below the slide rods and meshes with the ring gear - determine the placement on the bracket from a scale drawing with the rods and the lens centerline, or trig it out.

Buy a stock knob of your liking and mount it on a shaft on the L bracket as well (or an adjacent bracket) normal to the gears as shown in the picture.

The purpose of the system is to give precise motion to the camera with coarse motion from the knob; similarly low forces on the knob become high forces on the lens, which I believe is the reason for the pulley so you don't break the lens. The system also changes the rotation 90 degrees. You can accomplish the same 2 things with a flex shaft (like the FIRST seat motors). Attach one end of the flex shaft to the knob and the other end to the gear shaft. For these loads you can probably use set screws (forgive me Woody) to transfer the torque. You may need to restrain the flex shaft somewhere in the middle depending on the load but hopefully not.

Mount the L bracket(s) to the rods with saddle clamps - complexity of that attachment depends on how often you plan to take this on and off.

Good luck.

[anthony113]

wow you guys are hardcore. if i can get you guys the measurement around the cameras focus ring and some measurements of the base of the camera and all do you think you could CAD something like this? i have a few more facts to help you guys out.

the saddle bracket clamps on to two 15mm diameter rods that stick out of an aluminum base that mounts onto the camera. these parts would also need to be built to mount the follow focus system, however they are relatively simple to design.

its ok if the black knob turns infinitely in either direction, there is no stopper on the cameras focus ring. the ring is connected to a sensor which controls the cameras lenses. basically, the focus ring on the camera can be spun in either direction without causing any harm to the camera or lenses. the focus though is electronically limited.

there are two ways to approach the gear that interfaces with the cameras focus ring. you can either bore out a large aluminum gear and slide it onto the cameras focus ring, then use a gear on the follow focus to interface with it. or, you can design a more custom gear that would fit in the not so gearlike grooves of the cameras focus ring. heres a detailed picture http://www.frimu.nl/AG-DVX100.jpg the focus ring is the one to the left of the numbered ring. has little grooves in it. THERE ARE 30 "PEAKS" and 30 "VALLEYS" on the cameras focus ring. the distance around the focus ring is about 28.8mm.. not exactly sure though cause i took it with a crap tailors measure.

[Al Skierkiewicz]

Anthony,
You can manufacture this out of stock parts from almost any source. Check with Small Parts, Inc. though. I think your dimensions on the focus ring are off by a factor of 10 though, it looks more like 28 cm in circumference. The part is assembled from a right angle drive, (black knob is on the input shaft and the brass pulley is on the output shaft) two brass pulleys, belt and a mating gear for the larger gear. The part you show has a custom part to hold the right angle drive and the upper shaft (likely holding a bearing in the upper part of the housing.) The thumb screw on the bottom allows side adjustment to mate with the focus gear. You can buy the base plate from a camera store like B & H in New York and add you own arangement to hold it all in place. The rods are not a necessity but likely are used on other camera attachments from the same manufacturer. You might want to check with the manufacturer for a "studio kit" which might be cheaper and provide a remote focus knob that would be easier to use than this one.
A word of caution, messing with the lens of any camera is risky business. If you permanently distort the focus ring, or accidently over drive it, the cost for repairs is astronomical compared to the cost of the camera since this is not a removeable lens. It is possible to cause the lens to become a "fixed focus" if the ring or internal parts are damaged.

[anthony113]

Al, hmm i have very little experience when it comes to making things like this. if you would be able to recommend a list of parts i might need and a way to go about making the casing or structure to hold all this stuff in place and mount to the camera i would be very appreciative. thanks!

[Astronouth7303]

Interesting mechanism... I would agree that it looks like a focus tool (Most lens adjustors are). And you probably have more cad expierience than me.

[Aignam]

Maybe you could use emachineshop.com to manufacture your parts if you don't have access to a real machine shop? Anybody ever work with this website before?

[Al Skierkiewicz]

Originally Posted by anthony113

Al, hmm i have very little experience when it comes to making things like this. if you would be able to recommend a list of parts i might need and a way to go about making the casing or structure to hold all this stuff in place and mount to the camera i would be very appreciative. thanks!

Anthony,
I will look around but I am up to my eyeballs in a special project at the moment. This thing does not need to be that elaborate. A section of right angle aluminum, a few bevel gears for the right angle drive, some rod for the shafts, maybe a couple of small bearings, a small belt, (with pulleys for round belt you can use an o ring for this part) and a gear big enough to go around the the focus ring with a matching little drive gear, a hand full of set screws and other hardware, a plate to mount everything on that attaches to the bottom of the camera and a weekend ought to do it. There are little junk stores in most big cities that sell just what you are looking for or there are a lot of stores on line. Check out Small Parts, American Scientific or any of the online sources for RC car and robot parts and you should be able to pull it all together. You have a good start since you have seen a real one up close and you have plety of pictures. Just reverse engineer the parts, this should be fun. I know you can do it, don't be discouraged by the finished look of the part you have. It does not have to be designed that well to work for you. Remember the part you showed is engineered for constant professional use over years of service life with no failures and ease of movement from camera to camera throughout it's life. You can build a camera specific part for far less that will work great for you application and if it fails every so often, you fix what broke or slipped and reshoot.