Deckel Pentograph GK21/ pulley drive system

[Steve Wan 1Participant @stevewan1]

Dear all machinists,

Greetings!

Does anyone here owns a Deckel Pentograph GK21?

Could you share how the drive system work, the tensioning is constant regardless where the spindle head moves in any directions…something I like to apply to my external pulley system of my DIY horologist mill.

Thanks ahead

Regards.

Steve Wan

[Steve Wan 1Participant @stevewan1]

Deckel Pentograph GK21/ pulley drive system

[John HinkleyParticipant @johnhinkley26699]

Steve,

The lathes.co.uk site has some useful reprint material about the GK21, but doesn't show the drive system in any detail. If, as I assume that you don't have such a weighty machine and merely want inspiration for a similar drive for your horologist's mill, go to This link to Stefan Gotteswinter's site. There you will find his description of his much smaller Deckel G1L engraver. At abot 7:30 he demonstrates the belt drive system in some detail and I think you'll get a lot of good information there.

John

[BazyleParticipant @bazyle]

Not sure about the GK21 but I think the Alexander puts the motor on a swing arm and simply uses a spring in tube tension concept between the motor and workhead and they move together.

[William SParticipant @williams]

Good evening

Not a Deckel but I am the owner of an Alexander 2c engraver, which uses a very similar drive belt tension arrangement to a Deckel:

It is a very simple yet effective set up, basically the counterbalanced arm pivots on the bottom pulley spindle. The top pulleys are pivoting on the top of the arm. These pulleys are in turn connected to the spindle via a spring loaded rod, what actually provides the belt tension. I hope that helps, the most important part to me is the arm pivoting on the bottom pulley. Any other query’s I can try to answer, I can get machine out if you require a side on picture.
(I do apologise for the orientation of the pictures)

William.

[Steve Wan 1Participant @stevewan1]

Dear William

Wow! Great your Alexander 2c engraver looks similar to Deckel. Possible to dismental/ take photo the twin pulleys with swivel plate separately/3rd photo? The primary function of the plate is to swivel left and right but not up and down movements?

If that's not possible the front and side photo may help.

One more question, how helpful is the counter balance weight to the end of the pole in terms of the mechanical advantage?

Finally, I can get a go ahead to end this issue

Thanks a million!

Regards,

Steve Wan

[William SParticipant @williams]

Hello Steve

Sorry for the delay:

The following pictures are of the top jockey wheels, as you thought these swing left to right basically between centres! these do all the work changing direction of the belt.

Up and down is only about 1/2" on the "quill"/spindle down feed so the belt just rolls around these jockey wheels

The counter balance on the end of the pole I cant say it really does much to the motion, I not have noticed it anyway. the pole swings backward without the belt so It doesn't seem to do much.

(And yes the machine is in the house, right next to the front door in the porch! ideal as it was a wasted space anyway and its got brilliant sunshine in the afternoon though 2 windows!)

William

[Clive HartlandParticipant @clivehartland94829]

From my use of an Alexandar engraver the balance weight acts as a mass ballance when the pantograph moves, without it the movements would not be smooth but jerky. Incorporsate the weight if you can.

[Steve Wan 1Participant @stevewan1]

Hi William

Just realised your Pentograph photos are in!

All as I needed.

Thanks! Back to my drawing board to design and make the pulley drive, finally.

Thanks so much!

Regards,

Steve Wan

[Steve Wan 1Participant @stevewan1]

Hey William

Btw notice you need to get the Pentograph machine out of the storeroom.

Appreciates the heavy lifting you need to get it out to the open to take photos.

Owe you a cut of tea!

Regards,

Steve Wan

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