21 replies to this topic

[John Miele]

It's time to build myself a scope dolly to move my Atlas az-eq mount and AT130 triplet from the garage to the back patio for high power visual sessions with double stars and planets. I'll be moving about 110 lbs total weight with counterweights included. Surface to traverse is a fairly smooth concrete driveway and patio so I believe medium size casters, say 3 to 4 inches will suffice. I have seen scads of plans and I'm confident I can cobble up a workable design.

 

My concern is stability when observing at high power.

 

It seems about half the designs simply use castors only. And the other half only use the casters to roll into position and then use some type of screw levelling jack to provide a solid base tot he ground. 

 

I would appreciate any feedback on how stable your locking casters are at high power?  It just seems they would have to have some wiggle in them due to tolerances in the fit of the moving parts. Any advice on choosing a set of solid sturdy locking casters is also appreciated!

 

Basically I see a set of tradeoffs like this:

 

Option 1 - locking casters only:

 

Pros: simpler design. quick set up.

Cons: possible stability issues. Must do levelling with tripod legs..need room for legs to move on dolly. Need more expensive heavy duty locking casters.

 

Option 2 - non locking casters plus levelling feet

 

Pros: more stable. can use cheaper no locking casters. legs can stay fixed to cart. levelling done by the jackscrews.

Cons: more hardware to buy (threaded rod, handles, swiveling footpads) a little harder to implement in the design. more time to setup due to hand turning the levelling screw.

 

Thanks for any advice before I go buy the parts!

 

cs...

 

John

[Bean614]

"...I believe medium size casters, say 3 to 4 inches will suffice."

 

I believe you should reconsider!  In my experience with many different Scope Dollies, the Minimum Tires I would use would be 10" Pneumatic Tires.  You'd be amazed at how easy it is to have those things tip over with small casters--- even seemingly small pebbles, or small pieces of detritus,  can stop that thing in its tracks, and cause a tip!

  And, yes, definitely leveling jacks!

Edited by Bean614, 25 January 2021 - 03:51 PM.

[MikiSJ]

I would opt for having leveling screws to lift the three corners off the ground, or at least make their presence minimized. The make setting up and finding the pole easier, I would embed a cup into the concrete so that each screw will line up every time you use the kit.

 

Also, make sure the leveling screws are beefy enough to halt side to side vibrations. 

[Couder]

I have several I made. I use smaller wheels and large threaded rod with crank handle for leveling. I have not had any trouble with pebbles or rocks. I do have a place where two levels of concrete meet and it is about 3/8", so I am careful there. The big one doesn't have the levelers installed yet, the one leaning on the cabinet  has 1/2" x 20 coupling nuts welded in the end of the legs but the rods are off for ease of storage. 

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[nic35]

+1 on Bean's to use larger casters.  I went for 8" pneumatics (harbor freight) to carry around my CGEM and scopes.  My home-brew dolly consists of two 36" perforated steel rectangular tubes (big box store) bolted together with a u-bolt to form a T. 

 

I have had an unpleasant  experience with smaller casters "catching an edge" on what looked like an insignificant crack in the concrete !

 

I do not use use levelling screws.  For what I do - "observing" with a CMOS camera - they are unnecessary.  Live stacking, autoguiding and plate solving keeps everything under control.   

 

john

Edited by nic35, 25 January 2021 - 04:29 PM.

[mrlovt]

I'd go with pneumatic tires as they overcome irregularities in the path, but large casters should be fine - the larger the better for overcoming stones & debris.  Locking if you need the feature, but unless you'll be parking on a hill (in which case, I'd reconsider the whole project) I don't think locking the wheels or raising the buggy with leveling feet is necessary, even for high powered AP.

 

Now, my civic duty:  Telescopes are very top heavy.  Make sure everything is strapped/bolted/anchored down, lest you have a terrible accident and destroy your scope, like the fellow in this thread did non long ago.

[John Miele]

OMG! That was horrible!

[John Miele]

Wow...a lot of feedback to go with larger wheels and pneumatic at that.  I will upsize the wheel diameter then!

[John Miele]

I have several I made. I use smaller wheels and large threaded rod with crank handle for leveling. I have not had any trouble with pebbles or rocks. I do have a place where two levels of concrete meet and it is about 3/8", so I am careful there. The big one doesn't have the levelers installed yet, the one leaning on the cabinet  has 1/2" x 20 coupling nuts welded in the end of the legs but the rods are off for ease of storage. 

Do you have a pic of your crank handle? Is it something you made or bought?

[Oberon]

"...I believe medium size casters, say 3 to 4 inches will suffice."

 

I believe you should reconsider!  In my experience with many different Scope Dollies, the Minimum Tires I would use would be 10" Pneumatic Tires.  You'd be amazed at how easy it is to have those things tip over with small casters--- even seemingly small pebbles, or small pieces of detritus,  can stop that thing in its tracks, and cause a tip!

  And, yes, definitely leveling jacks!

This!

 

I get the horrors when I see top heavy 3 wheeled castor dollies. I get some people can be very careful and get away with it, but they are courting disaster. I wouldn’t consider anything less than 6” and bigger is better, 10” pneumatic are great.
 

And leveling jacks (or solid feet of some kind) are essential for high mag. Leveling jacks can be wobbly too.

[stevety]

get heavy duty medium jmi wheeley bar larger wheel i have no problems and roll into shed when not in  use .i have the 5" wheels

 

 

 

Edited by stevety, 25 January 2021 - 04:54 PM.

[markb]

I have used 4" wheeled chinese video 'dollys' (DON'T) and currently use a CN recommendation, a Manfrotto 114 with 130 pound capacity and 5" wheels for my 70+ pound GPS11.

 

I use the fully loaded with mount and ota  Manfrotto on the 'flat' only. I move the GPS11 over sills and curbs only on the giant wheel small dolly, below.

 

So far I am caster only (but a high grade caster), and jacks seem unnecessary so far, but I've had only limited use.

 

5" really should be considered an absolute minimum, I would prefer 6" or more.

 

5" wheels just make it over small rocks and large gravel, common here in Arizona, even in the backyard.

 

I may add jack screws later but am waiting to get more use to see if it is necessary. My tripod legs can handle the leveling part of the problem, and the weight loaded bearings in the wheels may be sufficient to keep it stable. The manfrotto has an unusually solid wheel lock mechanism that locks into a castellated washer.

 

A big improvement came with the simple addition of sorbothane squares made for compressor vibration elimination, also mentioned here on CN and available cheap on Amazon. 

 

I second the recommendation on 6"-10" blowing wheels on a home built.

 

I just finally tracked down an adequate cart for my GPS 11 Mount and OTA, and the biggest issue was wheels just under 7 in and diameter, and about 2 and 1/2 in thick, either solid rubber or foam filled.

 

They were referred to as tank wheels, and massively increased the stability of moving the GPS 11 on the cart. I'm still trying to get around to doing a posting on the setup, which included a 12-in square aluminum plate from Amazon to give an adequate base for stability.

 

Fat, essentially solid wheels really add to stability. inexpensive inflatable hand card wheels, on the other hand, may turn into a liability if they leak as much air as every Chinese made handtruck I've had in the last 20 years has done. If you go that route, at least buy top grade replacement tubes for the tires as the tubes are the weak spot.

Edited by markb, 25 January 2021 - 05:01 PM.

[rboe]

I have 5 or 6" urethane casters in the shop for a project that never seemed to get off the ground. Like these: https://www.amazon.c...1611470&sr=8-10

 

Now since they have never been used I can't speak to how well they worked; but I'm thinking they are soft enough to provide a nice ride and dampen vibrations. Not be pneumatic they won't suffer from punctures. A big problem in our yard, due to bougain villa bushes (which have taken out my dolly tires) with their nasty thorns.

 

I did use two rows of small hard casters on the bottom of my dob - vibrations were not a problem - on the grass. But it was a very poor design for the lumpy grass we have so I converted to two large lawnmower wheels. Tripods are harder design for, never went down that road.

[Couder]

Do you have a pic of your crank handle? Is it something you made or bought?

I made the crank handles, be sure your knob can turn or you'll burn your finger. Also, on the footpads the nut turns in the pad or it will chew your concrete up. You can see the 1/2" - 20 coupling nut in the picture. This particular "wheely" is for a much smaller scope.

 

I too dislike top heavy things, which is why I made my "wheely" things with a large footprint. I prefer the solid castors, maybe because the large scope is well over a ton.

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[MitchAlsup]

Casters are for moving.

 

Feet are for a stable position.

 

The two are simply opposite on the scale of moving to fixed.

 

So, either the casters lift up so the feet can hold the load, of the feet move down to lift the casters off the ground.

[mrlovt]

OMG! That was horrible!

Yeah, that was a bad day for the OP for sure.  And a lesson learned, I'm sure.

[Jon Isaacs]

Casters are for moving.

 

Feet are for a stable position.

 

The two are simply opposite on the scale of moving to fixed.

 

So, either the casters lift up so the feet can hold the load, of the feet move down to lift the casters off the ground.

 

 

The only experience I have had with casters is with my 12.5 inch F/6 Meade Research Grade.  It was top heavy and the wheels were small. There was a lip where the garage floor met the driveway.  I was very careful and made sure I pushed from down low so I didn't push it over.  It's wasn't the best but it worked. 

 

 

 

I really don't understand trying to observe or image with the scope still on wheels.  You pay big money for a stable mount, a real tripod capable of supporting the scope in the way it needs to be supported and then you leave it on the wheels... nice and flexible, especially if they have pneumatic tires. 

 

Consider a tripod with a 4 foot base.  Consider a deflection of 0.002 inches.   That is a rotation of 0.002/36 = 8.6 arc-seconds.  0.002" is slightly less than the thickness of an average human hair.  

 

As Mitch says, wheels are for moving.

 

Jon 

[jlcop]

I currently use a circular furniture dolly with non-locking  casters to move my 12' Flextube Dob. I drilled a hole in it's center to clear the azimuth bolt head. It works fine indoors on carpeted, concrete and wood floors. The only issue I've had is going over the threshold to our patio. I've made a diy ramp of sorts that still needs some work but is doable. Interestingly I have had no problems with the scope moving while in use with the non-locking casters.

That being said I ultimately will make or get something else with larger wheels for movement over more uneven surfaces. I may try my pneumatic tired garden cart with some kind of adaptation until I can acquire something more substantial. A custom built cart for my scope lists for $400 online. I think I can do better than that, especially if I can convince my wife's nephew to do the welding!

John

[rboe]

OK, possible solution. This kid does blacksmithing and he borrowed some ideas from other folks for his "mobile" vise stand that just may be applicable in this application. Basically a triangle with dolly wheels on each corner. One corner is hinged and fixed to one leg so the whole thing hinges up. Push it down, prop it with a stick to stay down - you have a mobile base. Watch the video, it'll make more sense.

 

14 minute video with about 30 seconds that will apply to this topic - sorry about that (on the other hand his videos can be neat to watch!).

 

https://www.youtube....h?v=h5EIfbQK3qw

[TelescopeGreg]

Here's what I built:

https://www.cloudyni...s/#entry8956030

 

In hindsight, I should have made it slightly larger (a little more stable), and put the tail jack on the outside so the swivel wheel wouldn't bump into it as it turned 360 degrees.  The jacks were actually an afterthought; don't make that mistake!  It would have also been better if the swivel wheel was pneumatic, like the other two, for vibration dampening during transit, but I couldn't find one in the right size. 

 

Most transit is with the two pneumatic tires at the "front", with the tail wheel dragging behind.  I push it with one hand on the mount's Elevation knob as a handle, and the other on the front side leg of the tripod.  It's pretty stable, but having 2 hands on it at all times is still a good idea. 

 

You can see that the jacks are already lowered and locked into place.  I image from the neighbor's driveway across the street (too many trees here), in the same place each time.  Those jack positions, when supported on 2x4 scraps, levels the overall scope.  They can be loosened and moved for other locations, of course.  The scraps are stacked and tied down for transport on the far side of the PowerTank in the picture.  The use of the 2x4s raises the effective ground level, which helps shorten the "throw" of the jacks, to give more stability.  DSO AP is incredibly sensitive to any sorts of vibration or movement.

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[duck]

had a 18.5" scope on steel casters and leveling feet.  It tipped over once when I towed it out of the shop with a car.  The leveling feet were questionable.  Used a jam nut on the top side.  That scope now resides in a dome.

 

Got smarter with my back yard scope which moves around the patio in order to get clear views, thanks to too many neighborhood trees.  Made three wooden disks with aluminum plated tops which when fitted under the corners of the pier will raise the casters off the concrete.  Then made a lever with some rollers and a shovel handle which lift a corner of the pier up.  The disks are then slipped under the pier.  This scope weighs about 500 lbs.

[John Miele]

Big thanks to everyone for ideas and inputs. I ordered these 6" casters and plan to use 1/2 inch threaded rod and levelling feet to jack it up when observing. I'm going to start a separate build thread when all the parts arrive.

 

https://www.amazon.c...2xpY2s9dHJ1ZQ==

 

John