Cool project and the table looks much more "human" in scale then anticipated after reading steel reinforced concrete. Also never heard of Alcantra before did a bit of reading on it sounds like cool stuff. Congrats and I hope it sounds as you intended. Not a TT or idler expert by any means so no comments as to the idlerness of your design.
My new Idler - but is it an idler ?
Some time after my rediscovery of vinyl, I started toying with the idea of building a turntable. At the time I owned an idler (Dual 1219) and a DD (Technics SL-QL1). For me, the Dual was a small revelation (although there was The Rumble) and started me on an If... path.
Put it simply, what about designing an idler with modern materials, technologies and principles ?
Almost 3 years later - and 2 prototypes - I think I might be getting somewhere. I leave some picts and details for your "viewing pleasure".
- Plint made from steel reinforced concrete containing all locating points
- Subframe from Aluminium / Acrylate sandwich
- Inverted bearing design with twin ceramic spheres as the thrust surfaces
- Aluminium Platter with an inner acrilic ring and underside rubber matting for damping control
- Epyciclic drive - the motor pulley directly drives the inner rim of the platter, so no real idler drive…
- BLDC motor with electronic control and speed switching
- Armboard made from an aluminium / corian sandwich
Externally, I used black Alcantara for finishing (no nasty fingerprints), with the sideboards made blackened mahogany. Later, (after loosing 2 stylus to an excited child…) I added a darkened acrylic cover with a tilt/slide opening.
Overall, the main drivers for the design have been speed stability, low background noise and resonance control - hence the several “sandwiches”. Speed stability is where I think some progress is still needed, but I have an upgrade coming along.
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Kudos to you for the effort, but one could say that there ARE commercially made "modern" idler drive turntables, if you count all those add-on rim-drive systems. I guess TT Weights and Trans-fi made or make "from scratch" rim drives, as well. Granted, rim-drive is not quite like classic idler-drive. |
I want to give a little more detail about something that took more effort than I was expecting: the pulley clutch. To save the pulley from eventually deforming by being always in contact with the rim, there’s a need for some mechanism to move it out of the way when not in use. From the start I used a simple vertical hinge consisting of an urethane strip. With power off, a spring pushes the motor / pulley assembly away from the rim. When power is back, a solenoid retracts the spring and gravity pulls the motor down and the pulley touches the rim. However, the pulley seldom contacts the rim in an absolutely perpendicular “true” way, ending up “riding” slightly the surface of the rim. This causes small speed fluctuations (wow) that sometimes can be heard. To counteract this i devised a more complex clutch, where the pulley approaches the rim in a completely perpendicular / true way, only applying pressure when needed. I'm quite pleased with the way it worked out. It looks good and it's noiseless when engaging / disengaging. In fact the pulley is always touching the rim, but pressure is only applied when On. I still have to measure the final result using PlatterSpeed / Adjust+... https://restlessengineer.files.wordpress.com/2017/10/20171013_194155.jpg?w=900 https://restlessengineer.files.wordpress.com/2017/10/20171016_093114.jpg?w=900 |