Introduction: Dobsonian Trolley Improvement
I made a wooden trolley for my Skywatcher Dobsonian 300p Flexitube Goto Telescope which has given me good service for a couple of years, but I felt that it could be better and more practical so after reviewing a couple of commercial and some homemade ones I came up with this design and build ...
I only had to buy about a dozen new nuts and bolts as I reused much of the original components from my wooden trolley. For completeness, I will list all of the parts I used - apologies if I miss out any parts but hopefully, the photos will help explain the supplies used. Obviously, the supplies could be varied depending on what you have to hand and modifications you may feel suitable.
- IKEA Nicklaus sides - other similar ladder rack sides are out there. The metal tubes of the IKEA ones are approximately 32 mm in diameter with a wall thickness of 2-3 mm
- One for main carriage
- One for cutting into cross-struts
- Two wheels (130 mm diameter) - Fully rotational - These go at the front of the trolley and allow the trolley to be steerable
- Two wheels (130 mm diameter) - Fixed - These go at the back of the trolley and are mounted outside the main frame piece for extra stability
- 16 Carriage bolts and nuts M6 x 50 mm - to attach wheels to cross strut
- 8 Carriage bolts M8 x 150 mm [The only things I had to buy new]
- Multiple washers and spring washers of appropriate size for the bolts
- Bracket for broom handle fixing - this is for the handle for pulling/pushing the trolley
- Metal plate for front wheel levelling bolt support
- Two U-Bolts originally for bolting an aerial pole
- Ten end caps - These are covers for the hinge holes in cupboard doors that just happen to fit!
- Three M8 x 120 mm bolts and captive bolts, plus three adjustment feet from the original IKEA units
- These are for levelling purposes in the field once the telescope is in position
- Lockite to secure the threads where I felt it was necessary
As you can probably see from the list and the few things I have to buy I am a bit of a squirrel ... but the result justifies the hoarding in my opinion!
Step 1: Initial Design
I had a couple of side pieces from an old IKEA Nicklaus shelving unit which has done service in a number of configurations over the years and I thought it might be usable for my purposes. Although I can weld, my skills are definitely rusty (no pun intended), and I do not have easy access to the necessary equipment. The appearance of the Nicklaus sides made me think that I might be able to use them with nuts and bolts to achieve my aims.
My initial plan was to use one of the sides to be 'outriggers' as I tried to show in the pictures in supplies but I quickly realised that they would not be needed and so only used one of the sides as a base. The circular disc in the photos is the setting circle from the telescope for size/dimension purposes. See my other instructable as to how I made this https://www.instructables.com/Telescope-Setting-Circles/
I also realised that I could make the centre of gravity of the telescope on the trolley lower by cutting the other side into pieces for cross-struts and so the design evolved.
Step 2: Cutting the Side Racks Into Component Pieces
I cut down one of the sides to approximately 110cm in length to be the main base. As a result of this, I had to relocate some of the thinner bars that cross between the main side bars that actually have long threaded bars in them to hold the sides together.
The remaining off-cuts and some of the other side bar were cut into two 50cm lengths and two 70 cm lengths. Some of the spare thinner bars across the side rack were cut into eight 6 cm lengths to act as the supports to drop the centre of gravity.
The various sizes were determined very much by eye after positioning the component parts and then rounded to the nearest 1, 5 or 10 cm for neatness! The first two pictures show the frames on blocks while I was positioning items and considering options.
The wheels were bolted onto the cross struts first to help in the positioning of the cross struts on the main base. I was careful to ensure that the rotational wheels at the front did not foul on the main base. I also made use of various cardboard templates to help me consider the appropriate positioning of the elements.
Hopefully, the pictures convey how it all went together.
Step 3: Drilling the Holes
Lots of holes were then drilled into the tubes so that it could be assembled with multiple bolts, nuts and washers. This was quite tricky to ensure that the holes were in-line with each other so that the bolts were aligned correctly. I used a drill on a drill stand to try and keep everything perpendicular but had to open out some of the holes to allow the bolts to pass thru all of the metalwork.
As I was using carriage bolts with a square profile just under the domed cap, I drilled a hole of the correct diameter for the bolt then used a larger diameter drill to form a countersink with less metal in it. A mix of a hit with a hammer and the tightening of the bolts pulled it sufficiently and formed the square profile to hold the bolt in place and flush with the bars.
Step 4: Dropping the Centre of Gravity
One of the objectives of the new design was to lower the centre of gravity for ease of moving the telescope and also for safety. This was achieved by using longer carriage bolts with spacers made from the 6 cm long thinner tubes. I decided that positioning the main base approximately at the same height as the axle of the wheels looked and felt about right.
Assembly is shown in the pictures above.
Step 5: Placing the Dobsonian Base
The two U-Bolts were positioned as shown by placing the Dobsonian Base on the frame and marking the position of the original three feet of the Dobsonian Base. The 'front' foot is placed just past the thin cross strut to limit movement of the Dobsonian base on the trolley.
Step 6: Levelling Bolts
The trolley is pretty much level after assembly and more so with the weight of the telescope on it, but I included the three levelling bolts should I be on a surface that needs a bit of an adjustment. Most of my observations are done either on my front drive or my back garden - both of which are suitably paved.
Three bolts were fitted to give a good tripod and the captive nuts are actually intended for wooden fitting, but using a few self-tappers/bolts, I was able to lock them in place. The original levelling bolts from the Nicklaus Unit were used with connecting nuts and Locktite. The front levelling bolt is mounted in a metal panel between the front wheels and can be raised sufficiently to allow the wheels to fully rotate. I have a couple of old furniture castor cups which I can use for the adjustment feet to go into to allow them to move more freely for levelling.
Step 7: Final Additions
In my hoard, I found some end caps that fitted perfectly over the end of the various cut tubes to avoid catching the cut ends.
I re-used the Setting Circle that I built a few years ago but changed the mounting method to simply put three holes for smooth aluminium bolts at 120 degrees to each other that can be pushed through once the circle is placed over the Dobsonian base. These bolts fit between the fixed base and the rotating part. There is a simple metal arrow that is mounted on a magnet to read the azimuth after the setting circle is set and aligned.
I had a suitable box with felt lining/padding that would sit on the rear cross struts so I added a securing block underneath it to hold it in place. This is for accessories (I have a battery-powered screwdriver with a socket on it to use on the levelling bolts) or to place lenses in when not in use. I'm thinking of adding a battery-powered red LED string light around the rim of the box for illumination and to make sure I do not trip over the trolley in the dark.
Step 8: Finishing Observations
The original wooden trolley weighed approximately 10.3 kg and the new metal trolley weighs 11kg. The weights quoted include all fittings (wheels, bolts, etc) which are common to both trolleys. The difference in weight is negligible but the lower centre of gravity makes the trolley feel much easier and safer to move. The U-Bolts and the cross strut holding the original three feet on the telescope base means that the telescope is very stable on the mount and does not move from left to right or front to back when in use.
I have not sawn off the excess lengths of the assembly bolts as they do not get in the way of the trolley in use - it might look a bit neater if I did. Overall, I am very pleased with the appearance of the new trolley.
I hope that this Instructable is useful to others and if you have any questions or improvements please add a question or comment below.
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