Chucky, my new dolly (pun intended) is indeed a monster. I've had one of those post-aha moments.

Here's the problem. The dolly is 3 1/2 feet by 5 feet to allow a rider and 028 Bogen legs at full spread with a jib. I'll need a pickup truck or roof racks to transport it. The only good thing about it is that I can put hinges on one side and use it for a door.

I now realize why dolly's like this have a tower attached. It removes the necessity for a heavy duty tripod...and therefore the width is reduced. I'm thinking about an effective re-design and was inspired by this http://www.porta-jib.com/spider2-lg.gif

I'm hoping someone like Dan, who's no doubt experimented can help me out here.

1. I have 4 wheel units mounted in custom fabricated U channel, each having two axles. The wheels are roller blade types mounted vertically.

2. Will these wheels track on curved 3/4" PVC pipe? I suspect that horizontally mounted wheels are going to be a problem.

3. I'd like to have all four wheel units able to rotate and have two of them also on articulating arms. This would mean that track spacing would not be an issue, as the wheels would follow it. I'm looking for the simplest bearing arrangement.

4. The redesign would have four extendable arms that could be rotated for transport.

I'm looking for any comments on any element of this before I start cutting and welding. I'd like to limit my wasting of time. The reward for your help will be a photolog of my work as a DIY guide.

This Bogen 3502 looks like a good candidate for a ball leveller. I'll need this for the dolly tower.

http://www.bhphotovideo.com/images/items/203536.jpg

I've found references to these here using the search function. No one seems to be using it for near it's rated weight of 30lbs. Is anyone using this leveller under "heavy" load? My jib will be mounted to it.

Anyone?

HA! Great minds... I saw the thread title and thought Chucky too. :D

Hi Dennis,

Pictures are worth a 1,000...

Is curved track really that important? If you put a short jib on that thing, you can get a ton of shots that you think you need curved track for. In 25 years of working in film/tv, I've only seen curved track used once. Really. Now, commercials and Music Videos probably use them all the time. Don't know, just guessing. How 'bout getting a stabilizer for the few times you want the curved shot?

If you insist, first I'd see if you can make curved track. I've tried it, and was never completely successful. If you can get the track right, you need to make each wheel assembly on the dolly so that it can pivot. In the end, I'd make a dolly with tires, then you can go in circles all day!

Dan
www.DVcameraRigs.com

Agreed with Dan--I virtually never see curved track on set, except for when we need to entirely circle something 360 degrees or more (and as Dan points out, this is usually more of a music video vibe). Making a perfect circle out of track is a very demanding set of tolerances, I've seen pro track fall short of the mark on more than one occasion (think about it: the ends need to join up perfectly with no bump, that means 0 warping or error across a massive diameter). For moves that require a little curve, we use dance floor. I think the Flextrack from Losmandy is pretty neat for those who really like to build in compound moves like those, although unless you have the rideable version of the dolly, it's tough to operate smoothly.

Charles and Dan, thanks for your replies. I don't envisage using curved track a whole lot...if at all. The bigger advantage I think in having the wheels articulate is that I don't have to worry about spacing the PVC pipe on a "rail bed". So hopefully I can just drop some pipe and let the wheels track it. My other goal is having a dolly that can be set with a wide track/tower for jib use, or quickly adjusted to a narrow track/tripod for indoor use.

I've been looking at the pile of aluminum trying to figure out what the best tower location/riding platform setup is. I've spoken to a friend of mine (engineer) to try and work out some potential flex issues. These are very interesting but expensive bearings that would have worked great: http://www.reali-slim.com/ I dropped the idea when one of the local bearings suppliers quoted several hundred dollars each for even the smallest.

Time permitting, I'll post a few prelim shots tomorrow night.

Hmmmm... I don't see how pivoting wheels would help "Track" the track. You would need something that floats like the flex track set up. If you want to just toss pvc on the ground, I have a simple jig I mention in my book: It's just a length of plywood with 1"x1" bits of lumber that make up a goove on each end for the pvc to fit into. The gooves are the same width of the wheels on the dolly. Lay the PVC down and slide the jig down it. In a few seconds its perfectly laid out.

You might want to re-think the wide wheel set-up. Even outside, sets can be pretty cramped places. If you wanted to set the dolly up for a large crane, I'd toss a ton of sandbags on the narrower set up. Also, keep in mind when you are outside, you are going to need a lot of shimming and screwing around with the track to get it perfectly level. So you might want to think of a system to support that bendy PVC for using outside on uneven sidewalks, grass, etc. As for dolly platform size, I just have one set of wheels and move them to different sized platforms. I have 3 that I use all the time: 12"x12", 24"x24" and 24"x36". The 24" square is the one I use the most. It has a short jib (goes up about 7') designed to work with it that I use in place of a tripod 98 percent of the time. Even with static shots, it's easier to dolly and boom the camera to where you need it than it is to move a tripod...even with a camera that is only 5 pounds!

Dan
www.DVcameraRigs.com

Ok Dan. I think I'll make it wide enough for a door, like your 24" platform, and do the tower on that. It will just be a matter of four extra holes for the extra wide capability...so I'll try it for kicks and giggles. Like my jib, this will be an exercise in over-engineering, but I'm thinking I'll be pretty confident renting the stuff out.

Your voice(s) of experience are just what I was looking for. With steel, mistakes are not too bad, with aluminum...they're expensive!

As promised, HERE (http://www.pana3ccduser.com/showthread.php?p=27363#post27362) are some pics based on tonights efforts. My apologies for the cross bulletin link, but I can't post pics here :-(

Your voice(s) of experience are just what I was looking for. With steel, mistakes are not too bad, with aluminum...they're expensive!

Boy, you got that right! I've got a barrel of bits and pieces from failed rig designs from the first book that I can't bare to throw out. R&D ain't cheap! I know all about the over-engineering sickness. I suffer from it myself.

Dan
www.DVcameraRigs.com

As promised, HERE (http://www.pana3ccduser.com/showthread.php?p=27363#post27362) are some pics based on tonights efforts. My apologies for the cross bulletin link, but I can't post pics here :-(

It only took 20 years for my in-line skate wheel arrangement to catch on, but boy, is it going like gangbusters now! Kick ass job there, Dennis!

Dan
www.DVcameraRigs.com

Thanks Dan.

The inline's work great, but they are pretty squeaky. I haven't tried talc, but that's next. One of the strengths of your idea, (and it sounds like this came from you originally??) is that an inline wheel probably is capable of 200lbs or so of static load. My thinking is that a guy like myself, pushing off the nose wheel on roller blades, probably exceeds 250lbs load. Toss four in there and you have a very strong wheel pod.

I'll have to post some video of the "arms" in action. It's a neat sight to be smoothly drifting along on the PVC, look down, and see the arms tweaking yer ride.

Johnson's Baby powder....the squeaks are gone and I smell like our 2 year old. It's a nice contrast to the, ah, aroma of vaporized aluminum.

Well, the indoor experiments with the articulating wheels worked great...outside not so great. The whole idea is to make it possible to throw down some 1" PVC and go without taking elaborate measures to space and level the track. What I found is that with the dual rollerblade wheels mounted upright, it simply doesn't track well enough. As soon as the ground is a bit uneven, it wants to jump the track as one corner of the dolly becomes unweighted. So basically after spending $100 on wheels and bearings, I'm thinking that the "skater" setup will work a lot better as the wheels opposed 90 degrees to each other must track a lot better. Also in my opinion, the lazy suzan bearings I used to allow the wheel pods to rotate have too much play in them. This collective play can impart a bit of a wobble to the crane. So those are going in favour of a pinion or bushing type arrangement.

The whole idea is to make it possible to throw down some 1" PVC and go without taking elaborate measures to space and level the track.

Ah, the holy grail of gripdom. Stop now before the men in the white suits arrive! (Flex track came close, but even it is still a pain in the ass on uneven surfaces). If you choose to accept this mission, keep repeating to yourself: "It's only a movie. It's only a movie." This thread will self destruct in 5 seconds.

Good Luck, Jim...er Dennis.

Dan
www.DVcameraRigs.com

Hah, now I'm getting a pile of spare aluminum too. I've got 16 great 82mm inline wheels, with about 40 feet on them, and new ABEC3's to boot in case anyone's looking. My wife will be so thrilled with the new wheels.

I don't need luck..I need the fortitude to keep flashing my visa all over town so every sports vendor will acknowledge my insanity.

I tried moving the wheel pod's axles closer as well as increasing the gap between the wheels to no avail. I've concluded that inlines will only work with a more "prepared" track which is not my goal. The 90 degree skater wheels will hopefully be better as will be the improved pod rotation setup. The lazy susan bearings are just not solid enough...as I was surmising originally. Tighter bearings with fancy spring suspension sounds nice though. If nothing else Dan, my little tale here is a testament to all the time you've no doubt put into your dvrig designs.

Several things to consider:

Inline skate wheels may be too narrow. Use skateboard wheels which are usually a couple of inches thick and will ride a little more easily and make less noise. Talc works well. I have used that on my curved steel Matthews track and it works like a charm, but, otherwise I never need it on the straights.

The trucks for the wheel need to pivot and slide as the dolly moves through the curve. Having a slot will help ensure a smooth curve. Also using an ultra hard plastic washer, or block helps make the trucks move with ease. the plastic is hard enough that even when a large tripod, jib, weights and sandbags are on it, it is still smooth.

Consider the width of the dolly. Most doors are about 28 to 35 inches wide, not sure what the industry standard is. My dolly deck is about 26 inches wide, but I have sideboards that I can bolt on to make the dolly18 inches wider for the great outdoors or larger rooms. With the narrow dolly I can still fit through doors. Industry standard track is usually 24.5 inches wide, center to center. There are a couple of other widths, but 24.5 seems to be the norm.

Having curved track in tiny NYC apartments is a help, because it seems like almost all jibs are too big and get in the way of the shot.

I am in the process of rebuilding the dolly, so that it can negotiate the corners easily. I had the wheelbase too long and only two of the four trucks could slide. I had a machine shop cut the other two trucks so the the pivot hole became a long slot. The trucks are chromed "V" track with a flat piece welded on top and two wheels on each side of the "V". The chrome trucks effortlessly turn as the dolly moves.

Thanks Mark. The new wheels are indeed 101a durometer skate board wheels. I agree that inline wheels are inappropriate mounted at 90 degrees do the rather large slip angle on a rounded wheel surface. Fortunately the bearings are the same though. I have some two inch aluminum L bracket with flat stock to weld to the top...just like yours.

Rather than using a slot, I'm articulating two of the arms. This means the dolly has a potential track width from about 24 to 34 inches as the arms rotate from fully inboard to fully outboard. I've found that two flanged bearings (like wheelbarrows use) and a bolt make a very low deflection rotating joint however I also have a selection of impregnated bushings on order to see if they will work OK. The nice thing about using bearings is that properly bushed, they can be torqued down a great deal for a very low deflection, but freely rotating joint.

With four rotating wheel pods, two of them on articulating arms, it's an absolute cluster off the PVC track. I'm therefore setting the pods up to be lockable for use off track. The goal of course is having one unit that:

1. Has next to zero setup time.
2. Has very low track prep time.
3. Is very smooth and stable enough for my jib.

The site that was hosting the pics had a double whammy of hack and database move...so my original pictures are gone. I'll update this thread with my next iteration.

Yeah, I couldn't see the pix. Curious to see it. Almost sounds like a spyder dolly.

My dolly is pretty much set up for track only, but it would be nice to have street wheels on it to use it as an equipment cart, or to dolly on smooth surfaces. But I would have to have some kind of steering system. Maybe on Version 2.

The spyder was my inspiration. I should have gone with their skate wheel setup right off the bat instead of doing the inlines.

Eh. It's an experiment. My dolly isn't exactly how I want it, It'll get a few more upgrades. I'm not too worried. Most people are just thrilled that I have a dolly, they're not too worried as long as it's smooth and quiet.

Ok, the redesign is now complete. This dolly now has rocking, rotating and articulating wheels. Basically you throw your PVC down, straight, curved, whatever, as long as it is 24 to 36 inches apart the dolly will track it. The skater wheel design works much better in this application than the inlines.


There are a few pics and a short video here. (http://my.tbaytel.net/guskers/dolly.html) The video shows the dolly going over bump created by putting a piece of 3/4" wood under one rail. This would have derailed the non-rocking inline wheels in a second.

Great Job! Congrats!

Dan
www.DVcameraRigs.com

Thanks Dan. I now, more than ever, appreciate the work you put into your designs. This project had about $140 in sunk costs, plus a good 10 hours in experimentation.

Well worth the effort! It turned out really nice. It reminds me of the Flex Track "floating" wheel design. You could probably get away with using something like their track. You should see what you can find in some sort of large diameter hose and try it out.

Dan
www.DVcameraRigs.com

Dennis, nice work. It helps that you can do your own welding. I've thought about learning. I'm going to look around for a machine shop that can do the metal work.

The only things I can thing of are: you may want to add some braces to the tower for stability, or perhaps a beefier tower? The one square tube just seems a bit too twig-like for my safety paranoia. Maybe make the back end of the crane a bit longer so that you won't need so much weight on the rear. As long as the tower is high enough, you won't have to worry about the back end bottoming out during the shot.

Nice job.

Some tips Jim Taylor, a great DP, gave me if you are going to be throwing down PVC: bring a couple of brooms to sweep the track area and also a few sound blankets to go under the track. The blankets eliminate the popping of grit against the PVC as you dolly and smooths out slight imperfections in the terrain. Just be sure that the blankies are not used for anything else as they get pretty nasty, pretty quick.

If you can find deals on steel track, it's worth it, especially with a set up as heavy as yours.

Mark, thanks for the tips on track. I've seen neoprene recommended too...same idea.

Because everything is aluminum, the rig looks a lot heavier than it is (about 60 pounds). In fact, I had no problem carrying the complete rig (minus the weights) from the shop to the yard outside. I considered bracing the tower but it's very stable as is. It's 1/4" wall 2 inch aluminum tubing...and what you can't see is the second collar below the tie in plate. So basically the base drops down about 6 inches into a second collar. It's the two that make it stiff. I did this to allow use of a tripod with the mast removed.

Okay, sounds good. If you've got the jib up high on a windy day how much do you think it would sway? I'm not being difficult, just making sure you don't get sued.

Well, the windy test with the cam fully upright is yet to come...plan B is a triangulated setup using stainless rod and a few turnbuckles. That's a last resort as I'd like to keep the platform clear. The skater wheel assemblies are much stiffer (near zero play) which contributes to a lot less platform wobble over the previous setup using 3" lazy suzan bearings.

One thing I've learned here though is that predictions and basic engineering don't always predict field performance :-)

Edit: Mark, I did some checking tonight. There's a couple millimitres of sway at the tower head when I force a wobble. That in itself is not a big issue...but a few mm at the tower end means a lot more at the jib head. I'll be adding a triangulated support system.