Wednesday, September 21, 2011

Gravity Ratchet re-design

I mentioned earlier that I had redesigned the drive barrel to be 60mm diameter instead of 25mm, so that the larger diameter barrel would have less build-up of string when fully wound. The build up of string creates more drive in the system, and the grasshopper escapement is sensitive to changes those changes. (I'm sensitive to ;)...) Anyway. So because the drive barrel is larger, it now blocks the view of the gravity ratchet which could be clearly seen with the clear perspex versions.

So I've decided to redesign it from being an 'inny' to an 'outy' and I don't mean to be like a belly button. Its basically been turned inside-out or outside-in. now its workings are even easier to see than the original. Nice! Its yet to be prototyped though, but I'm sure it will work great.

cheers
rosco

Friday, September 16, 2011

Final Build for the RB3

Finally here it is the RB3, and another clock that needs to be prototyped...for the 2nd time. There is a picture of the first prototype in the first picture of the post below titles "I think its there!" It is the all black clock on top of the speaker. Looks great! Ill upload a picture at the end of this blog.



But for now here is the redesign.
First of all I have to say that there has been some inspiration taken from a the clock plans that I bought for the making of my first clock which was for Seths 1st birthday. But really, to date the only thing that is even similar are the shape of the plates. There is also another version of this which will sport a childs name, a little mouse on the RHS and the poem "Hickory Dickory Dock" on the stand, which can be made for a childs gift. Which you can see in the earlier post "Seths clock remade with my new skills".
This redesign has a new escapement design with 1 degree of 'drop' and 'lock' instead of two, which should make it quieter, redesigned gear teeth, new drive weight reduction gears which reduce the amount of pulleys to 1 each side and a more modern face that allows the escapement to be easily seen. The CAD pictures above has weirdlt coloured parts, but I plan on making the real version of it in all black, with clear perspex on the numbers and hands only.
Antways...More to come :)

Wednesday, September 7, 2011

New Design with Gravity Escapement!

Here's my latest design!
Do I really need this now?...no. Can I stop myself?...no. So whats new?...nothing!
This gravity escapement has been in the works on and off now for just over 2 years. I don't have any instructions or dimensions for the design of it, I have just worked it out by watching animations of it on YouTube. There is a 2 impulse version of this escapement, but this is the Arnfield design with 1 impulse per 2 swings of the pendulum. This makes for a more accurate pendulum swing, as the pendulum is left alone for 3/4 of a 2 swing period. There is a little bit of recoil involved in its action, but still this type if escapement is regarded as being quite accurate.

Design of the clock...well it is the way it is, for a number of reasons. I find with a lot of things in life, that if you set a number of requirements, then you find everything else just fits into place. The first requirement was to have it to be able to sit on 1 wall mount instead of 2, as 2 can create issues with level, and also 1 wall mount may be bearing more weight than the other, so it might sag more and create twist in the chassis of the clock and in turn locking it up. The other requirement was that I wanted the gears to be grouped closely together, rather than in a straight line, to make it more compact. So I have used like a 4 leaf clover type arangement.

Then 1 last requirement was to use a Gravity Escapement, which has been the major contributer to the look of the clock. Firstly, I wanted the escapement to be visible, so, because of the way it impulses the pendulum, a simple design solution is to put the pendulum on the front rather than at the back. Also because the pendulum is on the front, the escapement needs to be at the bottom of the clock, so that the pendulum isn't projected way out the front to clear the hands and clock face. Also the use of a circle around the escapement so that it's curious action is nice and visible (see link below). So like I said, some simple requirements, for example the way the clock is mounted, shape and the ability to see the escapement and it kind of designs itself.
A major difference with this design compared to all my others is the pendulum length. It will be using a shorter pendulum with a 1/2 second swing instead of a 1 second swing. To my understanding, a shorter period swing gives a higher "Q" which increases accuracy. The standard Arnfield version of the Gravity Escapement...
http://www.youtube.com/watch?v=U6cUNi-SAOw
 ...has 6 spokes on the wheel (the thing that looks like a sun), but I have doubled the amount of spokes, which means that it will double the amount of time it takes to do one revolution...unless you half the period of the pendulums swing! Well, this is a prototype, so I hope thats the way it will turn out :)
Thanks for reading. Hope you have enjoyed this latest blog entry.
Cheers!