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Old October 6th, 2005, 10:41 AM   #1
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My dolly's a monster.

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.
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Old October 7th, 2005, 09:05 AM   #2
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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?
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Old October 7th, 2005, 12:28 PM   #3
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HA! Great minds... I saw the thread title and thought Chucky too. :D
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Old October 15th, 2005, 10:49 AM   #4
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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
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Old October 15th, 2005, 11:01 AM   #5
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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.
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Old October 16th, 2005, 02:52 AM   #6
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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.
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Old October 16th, 2005, 10:13 AM   #7
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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
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Old October 16th, 2005, 04:59 PM   #8
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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!
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Old October 17th, 2005, 01:21 AM   #9
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As promised, HERE are some pics based on tonights efforts. My apologies for the cross bulletin link, but I can't post pics here :-(
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Old October 17th, 2005, 10:15 AM   #10
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Quote:
Originally Posted by Dennis Wood
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.

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Old October 17th, 2005, 10:17 AM   #11
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Quote:
Originally Posted by Dennis Wood
As promised, HERE 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!

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Old October 17th, 2005, 12:52 PM   #12
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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.
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Old October 17th, 2005, 03:44 PM   #13
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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.
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Old October 23rd, 2005, 10:19 PM   #14
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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.
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Old October 24th, 2005, 10:06 AM   #15
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Quote:
Originally Posted by Dennis Wood
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
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