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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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31st May 2021, 9:36 am | #41 |
Octode
Join Date: Nov 2011
Location: Manchester, UK.
Posts: 1,872
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Re: Tell me the critical features of an idler wheel
I'm a bit put off by the CAD bit, but I guess (hope? ) I could get into it! A friend gets fed up with me asking to print this and that (and draw it, sometimes) - I have used most of the bits he has given me for patterns for alloy castings. Like the traditional 'lost wax' method for investment casting, people also report 'lost plastic' in various web videos - I've not tried investments, so this is something to look forward to.
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31st May 2021, 10:23 am | #42 | |
Hexode
Join Date: Jun 2018
Location: Buckinghamshire, UK.
Posts: 382
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Re: Tell me the critical features of an idler wheel
Quote:
I don't see the o-ring performing that function to any great extent. Cheers |
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31st May 2021, 11:04 am | #43 | |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Quote:
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31st May 2021, 11:14 am | #44 | |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Quote:
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31st May 2021, 11:16 am | #45 | ||
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Quote:
Yes I'm not convinced that the O-ring will work well, but it is a cheap starting place |
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7th Jun 2021, 6:15 am | #46 |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
hello all
Sorry for the delay in updating. Ive been waiting for a specfic size o-ring to come in and also waiting for a friend to find a knackered old idler I could practice on. No progress on an old idler yet BUT I got the o-ring today. In a what-the-hell moment I fitted it to my plastic printed idler which I put on a temporary analog of a real de-rubbered idler wheel, snapped them together (no glue) added the o-ring and put on the BSR idler wheel spindle with a circlip. So no bearing and very lose/wobbly on the shaft. Put the platter back on, put on my test 45 (a well known track so I could judge the speed) and everything worked amazingly well See photos attached, sorry the idler and analog is black plastic as it makes it harder to see the details and o-ring but black was what was loaded in the printer. Now obviously this is not a longterm prospect as it has no bearing whatsoever, but I think it proves many concepts such as the o-ring contact point seems ok (rather than square), the v groove seems to work well even without glue, and the line up to the various speed steps works well Where to from here? well I need an old metal idler to try this out on, I'd like to try the o-ring driving at 33 a record changer cam (will the o-ring transmit enough torque etc). I'm almost thinking can I print the whole thing in plastic and just lightly press fit a plain brass tube as a bearing!! watch this space Joe |
7th Jun 2021, 10:39 pm | #47 |
Heptode
Join Date: Jan 2016
Location: Wolverhampton, West Midlands, UK.
Posts: 777
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Re: Tell me the critical features of an idler wheel
Joe, I have really enjoyed reading about your design process and the responses that remind me how great a tool the Internet is for designers.
It's great to see the early results, please keep us up to date when you have time. I think your work has borne out the earlier comment about the myth of unobtainium too, to put the cat among the pigeons! Cheers from Bill. |
8th Jun 2021, 11:17 am | #48 | |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Quote:
thanks Joe |
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8th Jun 2021, 11:38 am | #49 |
Moderator
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Location: Exeter, Devon and Poole, Dorset UK.
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Re: Tell me the critical features of an idler wheel
Although I'm not much of a record player collector (but I do have a few) this is good news.
It's all very well being able to get fancy Idlers for your 301 but it's good that lesser turntables may have the opportunity of fresh rubber at affordable prices. I am following your progress with great interest. Cheers Mike T
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8th Jun 2021, 12:54 pm | #50 | |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Quote:
Obviously my 3d printer cost me money (A$350), and I need a computer and CAD software (software is actually free), but once designed you don't even need these, you can send away your CAD files to a company who prints it on a very accurate $3000+ printer for about $20 and they mail it back So if I can get the bearing bit sorted or can use the old idler body to mount my new O-ring holder, it could indeed be a viable option for anyone |
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18th Jun 2021, 11:29 am | #51 |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Hello everyone
Here's a progress update. Still haven't been able to get a damaged idler wheel to practice on, but I have ordered some oil impregnated bronze bearings that are incased in copper so can be glued into the plastic idler. Downside is they are coming from China so will take at least 6 weeks! In the meantime I decided today to make my own very simple bearing from a piece of brass tube. This has been cut and press fitted into the 3D printed idler, the results are very satisfactory (see photos). the previous idler was just a prototype and had no bearing so it was wobbly on the shaft and didn't sound brilliant but proved a few principles. Now with this new version with the simplest of 'bearings' there's no wobble as the bearing makes it fit well and the sound is as good as with the real idler I swapped back in. Whilst I'm waiting for the proper bearings my next test will be to see if the plastic idler, with O-ring and simple bearing can transmit enough torque to drive the cycle cam on a bigger BSR record changer deck Cheers Joe |
19th Jun 2021, 7:49 am | #52 |
Heptode
Join Date: Oct 2007
Location: Birmingham, West Midlands, UK.
Posts: 615
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Re: Tell me the critical features of an idler wheel
I'd be interested to know how much rumble you get in the sound due to an 0 ring having less amount of rubber to absorb lower frequency vibration?
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19th Jun 2021, 8:16 am | #53 |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Can you recommend something that would have such low frequencies? My test album was a Booker T greatest hits, whilst being excellent music it also was a really good audio test as sustained organ notes are easy to spot speed variations. It sounded awful with the old un-bearing'd wheel but very good with the new wheel with bearing
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19th Jun 2021, 8:26 am | #54 |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
I did also think about using 2 o-rings, one inside the other, this would double the amount of rubber horizontally. So I still have this option up my sleeve if rumble is a problem
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19th Jun 2021, 8:49 am | #55 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Re: Tell me the critical features of an idler wheel
Rumble ought to be OK if the idler's bearing is a good fit.
The round section of the O ring compared to the flat face of the original idler rubber will mean there is more pressure from the motor shaft (real pressure force/area of contact) and so the motor shaft will press further into the rubber, assuming the rubber to have the same hardness. So the idler diameter will act as baing slightly different to the motor than to the turntable rim. This will create a different speed error to the flat-surfaced idler, worse for the slower speeds there the motor saft diameter is smallest. I'm hoping this comes out insignificant on the speeds that people use 78, 45, 33 and I don't suppose anyone is much bothered with 16. I'd thought a bit about the flat cross-section of the contact face of original idler wheels and wondered why they'd gone to trouble to make them flat. Was it easier to make? or did it confer some advantage? I'm unsure of the speed effect. In simple geometry, the input radius seems smaller so there might be a speed-up effect, but then the rubber is elastic, and it's the rate of passage of its elastic surface in metres/sec that counts, and that surface is deformed around the drive shaft due to the applied force from the spring so length isn't a constant. Whatever it does, I think it will do a bit more of it with the round section tyre, but I hope it all comes out as insignificant. David
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19th Jun 2021, 9:38 am | #56 | |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Quote:
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21st Jun 2021, 6:51 am | #57 |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Hello everyone
Here's another update. At the weekend I got a damaged BSR idler wheel to practice on, and it's quite an interesting thing which means some of our assumptions were wrong and some elements of my designs need to change. See photos. First thing to note is the rubber part is not 100% rubber at all, it sits on a metallic extension of the central idler wheel. So the debate about whether an O-ring will provide enough shock absorbing characteristics compared to the real idler is now academic, the solid bit of rubber at the edge of the wheel actually provides LESS solid rubber than a 3.5mm o-ring Note how the rubber has buttons molded into it that fit in the holes in the wheel. The next puzzle was why so many holes? at first I was impressed that BSR cared about locking the rubber to the wheel thinking it was to do with torque transference (well not slipping) but I thought surely 3 holes would do that not 12. But I think I now know what's going on, the 12 holes are really to stop the rubber part moving vertically rather than slipping axially (ie stays horizontal and square) Anyhow I'm very impressed with the care and thought that's gone into the idler wheel from BSR, the buttons are somehow moulded right through the holes and attached both sides to the rubber. Rubber part moulded in situ, i don't really know? Who say the British don't ever over-engineer things?! So the fact there's a hidden extension to the metal idler wheel has upset my design and made it all a little more complex. There's now not enough gap beyond that metal lip to make a one piece plastic o-ring holder, so now I've had to make the O-ring holder in 2 identical parts (again see photos). I moulded 6 buttons on each, 60 degrees apart so they both mount in the 12 holes in the wheel in a balanced way, and then superglued them to the wheel and to each other through the holes. I'm hoping this will be strong enough to not be prised apart when I squeeze a tight O-ring into the groove. I won't be trying this for 24h as superglue needs to fully cure I will report back So I currently I have 2 designs in the mix: 1) add a replacement for the rubber to an existing idler wheel. pros - uses existing bearing, ends up looking like a real idler wheel. cons - has to be a special design for each manufacturers idler wheel which is a pain 2) make the entire idler wheel from plastic and an O-ring. pros - easy to modify the design to print a larger/smaller, taller/shorter wheel on a different sized axle. cons - hard to fit a bearing to a plastic wheel, may not have enough mass to drive a changer's cycle cam I'm still not yet sure which is the best approach cheers Joe |
23rd Jun 2021, 7:29 am | #58 |
Hexode
Join Date: Oct 2020
Location: Bridgewater, Tasmania, Australia
Posts: 473
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Re: Tell me the critical features of an idler wheel
Hello everyone
Here's another update Some failures, some successes, but definitely interesting findings I tested my 2 design options on a BSR UA25 record changer. I loaded it with 5 LPs and set it off. Not that I ever use a stacker but it's a good test for the driving power of my designs because if it can drive a platter loaded with 4 LPs and still drive the cycle cam for the 5th LP then that's good enough. So the results... test#1 - The idler wheel using an old idler metal centre and bearing with my add-on O-ring did not work! Spun the platter ok, but couldn't drive even the first cycle to move to the next record test#2 - My totally plastic idler wheel (with brass tube as a temp bearing) did complete the test right to the 5th LP. So what was the difference? The idler in test#1 was the exact diameter of a real BSR idler. the plastic idler in test#2 was 1.9mm bigger. not a big difference but I think it proves that the round o-ring with its smaller contact surface to both spindle and platter does indeed NOT drive as strongly So I printed another idler for test #1 1.9mm bigger and it worked just as well as the full plastic idler. So size does matter! Other interesting problems I had were with the neoprene O-ring itself From the packet it had a thin layer of oil on it, once cleaned it was still too shiny, I had some difficulty making it dull and more friction-full (new word), but when roughed up it worked well. Also there's a tendency to roll the O-ring into the groove, this is a mistake and can leave a subtle twist in the o-ring, best stretch it then slowly release it evenly into the groove (easier said than done). I wonder if this twisting motion is why people complain about the £150 commercial idlers that also use an o-ring? Second thing is both designs exhibited more wobble than a BSR idler (and by wobble I mean the arm that presses the idler against the spindle moves/jiggles constantly). I think the bsr idlers are actually ground exactly round at the factory to finish them (another reason for the square edge I think). With a lathe or even a matchbox squarely placed against the idler whilst rotating I reckon I can stop this wobble, but it's an extra hassle that I wanted to avoid, but realistically it makes sense that it has to be ground perfectly round. Does this wobble impact playback? well I couldn't hear any difference So a few questions for you all out there: 1) Will a diameter difference of +2mm make any difference to anything? 2) what problem could a slight wobble cause? look forward to your comments cheers Joe |
23rd Jun 2021, 11:52 pm | #59 |
Banned
Join Date: Jun 2015
Location: Mareeba, North Queensland, Australia
Posts: 2,704
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Re: Tell me the critical features of an idler wheel
As you are changing a drive chain using wheels, changing the diameter MUST change the end speed result. For old fashioned "record munchers" ( my name for record stackers ) it probably won't matter at all.
If you have some slow piano or violin music, the wobble will most likely be audible. In fact with a bit of modification you could make a mechanical true vibrato for guitar heads, using a speed variable motor setup. ( read lots of money made for the gullible ) Still watching this thread. I have a spare 401 idler that I have been thinking of sending down to see what you can make of it. These idlers also have in inner bearing sleeve that causes problems though. Great progress !!! Keep up these posts.. Joe |
24th Jun 2021, 8:57 am | #60 | |
Moderator
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Re: Tell me the critical features of an idler wheel
Quote:
With idler driven turntables it's the diameter of the motor pulley and internal diameter of the turntable that control the speed.
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