MadModder
Gallery, Projects and General => Project Logs => Topic started by: Meldonmech on February 29, 2016, 11:58:03 AM
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Hi Guys
It is a while now since I finished my last project, and I was beginning to get itchy feet. I felt like a challenge, the grasshopper escapement has always fascinated me and I started searching the internet for grasshopper clocks. There were many wooden ones, but I wanted a brass one. I eventually found one in the Model Engineer, A Grass Hopper Clock by W. A. Smith which was later published in book form, so I purchased the book. After reading the book several times and digesting the contents, I considered all the items and facilities I would require, and the only thing missing was the main spring. It is a non standard item for English Fusee Clocks and I tried all the usual suppliers without success, then remembered Meadows and Passmore my luck changed they had them in stock. Well bingo game on, decision made. The clock should look like the one below when completed.
Cheers David
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Hi David,
Looking forward to seeing this project come to fruition.
Grasshoppers are fascinating to watch.
My skeleton clock has been put on the back-burner whilst I get on with jobs on the house.
Cheers.
Phil.
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Yes, I look forward to this as well.
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Hi Guys
Thanks for you interest. Phil, I understand only to well how you can get bogged down by jobs around the house, as I suffer from the same problem. I have told my wife that I will do one house project, followed by one workshop project from now on. Keeping my fingers crossed.
Cheers David
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Hi Guys.
Smiths book is American,was published in 1990, and uses imperial units, which is fine by me. He uses American threads and I do not possess the necessary taps and dies so I plumped for the English BA threads. I found a useful table on the internet entitled "BA Thread Substitutes", which details BA, American, and Metric sizes.
The clock design specifies rear winding, bearing in mind the weight of the clock, and the delicacy of the escapement, options for modifications to convert to front winding are being considered.
It was raining yesterday, so I decided to make a start on the plates. The book includes a full size drawing of the plates so I took a full size photocopy. It suggests that this be glued to the brass plate using 3M Scoth brand Spray Mount. I did did not have any to hand , so I used strong wallpaper paste. When dry I securely clamped down the plate and set about cutting the two separate plates ( the back is different from the front). A Jig Saw was used to complete this task. Cheers David
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.........so I took a full size photocopy.....
David,
forgive me for mentioning this as I'm sure you'll have checked, but for anyone else reading - some photocopiers can slightly alter the size of a copy so its not 1:1, and more reprehensible are those multi-function devices with a scanner & printer which scan & print, quite often with a slight reduction in size to fit the whole of a scanned A4 page onto an A4 sheet where the printer can't quite reach all the margins.
Dave
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Hi Dave
Thanks for pointing out problems with distortions when photocopying from books. Luckily the plates drawings in the book covered a double A4 size, and proved to be true size when 1:1 copying. However many of the detail drawings in the book look to be full size and are not, this is going to make a lot of extra work as they will need to be re drawn before they can be used.
Cheers David
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Presumably the detail drawings have at least one dimension on them? Scan them then zoom until the scale is correct and print them.
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Hi Andrew
Thanks for your suggestion, got a new all in one printer, for my Birthday last week, have not even unwrapped it yet, been too busy trying to make some headway on the clock. I must have a break and read up on the facilities, could save a lot of time if will zoom.
Cheers David
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David - you can zoom using it in "copier" mode but steps (typically 1%) may be too coarse, and actually you don't need printer or scanner to zoom - as Andrew alluded, just scan it to an image, open the file and then adjust the magnification/scaling before printing.
Dave M.
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That looks one big sheet of brass!! Is it cz120 and what thickness? - just out of interest.
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Hi Dave
Thanks for the tip, will give it a try.
Cheers David
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Hi Chris
The 1/8" brass sheet is not CZ120. It is a semi hard brass of unknown spec, which has proved to be satisfactory in the past. The book suggests 3/16" for the plates to ensure stiffness of the frame. I have plans to modify the clocks design should my plates and frame need extra stiffness.
Cheers David
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Hi Guys
When using the jigsaw to cut out the clock plates, the upward action of the blade lifted the paper template in places making it difficult to follow the line. I had to stop several times and make quick drying adhesive repairs, so I would not recommend the use of wallpaper paste.
Cheers David
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Hi David,
I've used Pritt Stick for similar jobs. The paper (and Pritt Stick residue) comes off easily when soaked in water.
Cheers.
Phil.
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Thanks Phil
I have some, next time I will give it a whirl.
Cheers David
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Hi Guys
Made a bit more progress, I clamped the clock plates together and drilled and tapped the register holes for the two 4BA screws. The clamps were then removed, and small 2mm dia. holes drilled where necessary in the frame to allow entry for the piercing saw blade. The cut outs were then sawn.
Next job, a bit of physical, which I am not used to these days, especially when it comes to filing. By the time I had a full day of it, I vowed my next job would be machining.
Cheers David
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I can well imagine you being a tad tired filing brass all day. Well, filing anything all day really, but as I understand it brass is best filed or machined with tools that have not been used on iron, steel etc. Frankly I don't have the room or cash to carry tools specifically for one metal over another.
Good work so far,
John B
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Hi John
Thanks for you comments
Cheers David
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Hi Guys
Made a start on the frame washers. Ground a couple of round nose tools to produce the inner and outer rings. Turned the outside diameter, center drilled the bar, then drilled the hole. Next I produced the rings, and finally parted off, using a parting off tool in the rear tool post. Six washers, finished and ready to go.
A nice relaxing and enjoyable exercise.
Cheers David
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Lovely work!
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Hi Chris
Thanks for the comments.
Cheers David
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Hi Guys
The next job on the agenda are the frame pillars, and these need some special tools to be ground. The first pic. shows these tools, the most difficult to grind is the outside form tool, which needs both front and side rake. These angles must be made at the same time maintaining the profile. A piece of silver steel is used to check the form.
A bar of brass was faced up each end to the correct length. The 1/4 inch dia. spigots where turned, center drilled and tapped. The collet chuck was set up in the lathe and the work piece held, by the chuck and tailstock center. The position of the fancy turnings was marked out, then cut with the form tools. The top slide was then set to the required angle and the taper turned. The pillar was then reversed and the opposite taper turned. Finally the form tool was used to produce the radius at each end.
Cheer David
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Hi Guys
Finally got round to machining the feet. The brass bar was cut into four near finished size lengths to save material. The bar was then faced, drilled and tapped 2BA. The job was then reversed and the top diameter turned. This was used as a spigot, and held in the lathe collet chuck. The taper was turned, and radius on the rim turned by hand using a specially ground tool. Next a mandrel was made and attached to the base of the foot using a 2BA screw. This enabled the radius on the top rim to be completed. The top of the foot was then drilled and tapped 12BA.
At a glance I thought this looked quite a simple straight forward job, and was surprised how involved it was to make four feet all exactly the same.
Cheers David