Bobweight WIP

[Yojevol]

It's about a year since I started my latest clock project; downsizing and house moving activities have recently taken priority. I've had all the gears made for some time, so the next job is to make the pendulum. Yesterday I was hunting around in my now much depleted woodstore for something to base the bobweight on. I came across this:-

A piece of laburnum which was at the end of a 4ft slab. Just the right size to make an elliptical bobweight
Here is how it will be cut out.

The black lines indicate how the block will be scooped out from the rear side.
Firstly the whole surface apart, from the outer rim, will be lowered by 4mm. This space will eventually be filled by a lid panel made from the same wood.
Next a central channel will be formed. This will house the pendulum shaft the position of which will be adjustable to get the timing right at 1sec per swing.
Finally the 2 side chambers will be scooped out. These cavities will take lead shot if extra weight is needed. The 4 blobs are for 4 lid retaining screws.

Now to get my CNC router set up to do the difficult bit.
Brian

 

[J-G]

How will you be managing the 'length adjustment' Brian? - A captive screw on a threaded bar or a simple clamp? (are there other ways?)

 

[Yojevol]

How will you be managing the 'length adjustment' Brian? - A captive screw on a threaded bar or a simple clamp? (are there other ways?)

My 2 previous clocks have had a captive nut in the end of the pendulum shaft but this needs a bore above the nut for screw to go into. This time I'll do it the other way round - glue in a threaded rod which can be cut off to length once the pendulum length is established.
Brian

 

[J-G]

My 2 previous clocks have had a captive nut in the end of the pendulum shaft but this needs a bore above the nut for screw to go into. This time I'll do it the other way round - glue in a threaded rod which can be cut off to length once the pendulum length is established.
Brian

!! Of course I meant Captive NUT !!

Don't you consider that there will always need to be some adjustment available? Even if the clock is kept in the same place, there may be a change in the length simply due to prevailing conditions but if the clock is moved to a different location it will need re-calibrating. What is the pendulum rod made from?

 

[Yojevol]

!! Of course I meant Captive NUT !!

Don't you consider that there will always need to be some adjustment available? Even if the clock is kept in the same place, there may be a change in the length simply due to prevailing conditions but if the clock is moved to a different location it will need re-calibrating. What is the pendulum rod made from?

Yes I'll leave sufficient adjustment to cope with a few years of global warming. The pendulum is basically ABW - only because I had a scrap long enough. It's got a veneer of rosewood to tie it in with the plywood pallet, also veneered in rosewood.
Brian

 

[Yojevol]

Here's today's effort:-

I did a trial run on the Denford with a scrap of ply. Good job too, it threw up an error in the coding which resulted in the outer wall thickness being way under size. It was due to lack of an instruction to change to a smaller diameter cutter for the outer elliptical shape.
For the real thing I changed the routine to use a 6mm cutter throughout.
Tomorrow I'll bandsaw off the wastewood and finish the outer shape on the table router using a straight cutter with a follower bearing.

Brian

 

[Fergie 307]

That will look really nice. My long case has the Bob out of sight in a solid case. Just as well as it is just a fairly crude lump of iron! Looking forward to seeing the finished clock.

 

[Fitzroy]

I read the title as Bodyweight WIP and thought I so need to do one of those!

 

[J-G]

Tomorrow I'll bandsaw off the wastewood and finish the outer shape on the table router using a straight cutter with a follower bearing.

I'm interested to know why you didn't use 'Tabs' on the outline cut and go right through on the Denford. This would leave you just a little cleaning up of (probably) 4 spots.

 

[Yojevol]

I'm interested to know why you didn't use 'Tabs' on the outline cut and go right through on the Denford. This would leave you just a little cleaning up of (probably) 4 spots.

Good question. I'll let you know in the fullness of time.

Things were delayed yesterday; had to get a car tyre puncture repaired. However I managed to get the back panel made:-

Brian

 

[Yojevol]

Managed to bring together the bob, shaft and pallet yesterday. Mounted it on the workshop wall and gave it a swing.
The timing turned out to be remarkably accurate for a first stab.
Check out my video:-

'I'm pleased with that' as they say on RS
Brian