and now for something completely different......

cressy · Post by **cressy** » Fri Jul 25, 2008 11:01 pm

well not that different as a matter of fact, its just not an amp. same fare as usual from me, surprise surprise, im starting a new turntable.
ive been collecting bits on and off for the last 6 months to revisit the idler idea i had with the lp12 lenco idler from a few years back. this time im not using a lenco motor or anything else that was in a deck before apart from platter and bearing, i cant get away from that as i dont have the tools to make such a thing. i have a bearing and platter from some french broadcast deck, a dc motor from an industrial robot, another bearing for the idler out of an old trio deck and a variable dc power supply from a bike wheel balancing machine. having run the motor off this supply it will go from 0 to 3800 rpm, (measured with a strobe gun off a mate thats for setting the timing on cars) so have ample revs for whatever motor pulley i have made. this was run off a 24v laptop supply. i have a motorbike battery i can try too if needs be. the plinth sections are to be made from some huge 5" square by 20" oak blocks that were nicked off a building site 30 years ago by my grandad (see where i get it from!).
the plan is for the platter, bearing and arm to be mounted on a T shaped section and the motor and idler on a C shaped section that fits around the downward part of the T. i.e C-I (Join the hyphen to the i, shove the c further towards it. not a great description but i havent got the drawings as i did them at work in a bored moment) the T will be sat on foculpods and the c bolted directly into a large granite chopping board i came across on the flea market.
if anyone can help with making a motor pulley, and a disc with a hole in and a groove around the edge for an o ring to sit in for the idler, give me a shout, i'll be happy to send beer tickets your way.
i'll post some drawings when i get them later this week

cressy · Post by **cressy** » Wed Jul 30, 2008 2:57 pm

ive been doing a bit on the new deck today, finally got started after sneaking out of the house under the pretense of doing something else. first i cut one of the oak blocks roughly to length just to make it easier to handle as theyre bloody heavy. i measured the centre for the outrigger for the bearing 6 inches from the front as i want the platter to line up with the front edge. stuck it through the saw then measured an inch either side of the centre cut for the sides of the joint. a couple of passes and abit of work with a sharp chisel left a notch for the join.
i stuck the second bit through to make the 2 shoulder cuts and tenon for the joint.
then using no finesse whatsoever, i proceeded to bash very hard on the end of it with a lump hammer to force it into the notch. it was neasured so that it was abut 1mm larger than the notch to provide a resistance fit as i didnt want any glue or other fixings in there. a little sanding to see what the wood looks like under at least 40 year old varnish, and thats one bit of it on its way to being done. with a bit of glass on the top to look like a platter i doesnt look bad and gives an idea of what it will look like.
time for a cup of tea and a cig methinks as ive still got to make a whelping box for a pregnant chihuahua.......................

cressy · Post by **cressy** » Wed Jul 30, 2008 3:02 pm

a couple more pics of it fitted together and abit of mock up. next thing, a surround for the granite base, rounding the edges with the router and obviously a lot of sanding!

cressy · Post by **cressy** » Mon Aug 04, 2008 8:39 pm

now have the bearing in and the platter on, looks abit more like something, having taken the bearing apart its a grease bearing. the grease looks abit crappy. the only stuff i have is a tube of coppaslip copper grease. any suggestions on replacement grease or is coppaslip or a standard motor grease any use?

cressy · Post by **cressy** » Tue Aug 05, 2008 10:31 pm

been having a bit of a think about the construction of the motor section of the deck today, the initial idea was to have the big c shaped section with the motor and idler mounted in it. thinking on im not sure this is the best solution. there will be a hell of alot of mass to soak up motor vibes but that didnt really work on the lp12 idler. i thought of drilling through the granite base and adding a spike to the bottom of the motor casing that goes through the hole and into the shelf. adding a set of feet to the granite base should isolate the motor from the deck as the vibes from the motor would have to get back up through the feet, 11kg of granite and 8kg of oak to get into the platter. hopefully this would minimise the vibration tranferred up the motor shaft and into the pulley and idler wheel. or am i thinking along the wrong lines as it was this vibration issue that forced me to abandon the lp12 idler. btw, can anyone run up an ally pulley for the motor,? im having abit of trouble getting the local engineering firms to do a one off at the mo. cheers guys

cressy · Post by **cressy** » Fri Aug 08, 2008 4:16 pm

i got abit more done today, got all the edges routed over, gave it a good sanding with what paper i had to hand and attached the bearing properly on its own mounting plate. the motor unit and idler are going in the back right hand corner on their own block with the power supply attached to this. it looks rather nice on the granite base and the foculpod isolators. starting to take shape now

cressy · Post by **cressy** » Sun Aug 10, 2008 2:32 pm

i did abit of experimenting with some idlers last night, using what i had to hand. first i tried an mdf idler using a 3" rubber o ring that was a belt for an old hoover (god knows where that came from) as the drive face. i used a main bearing from an old trio deck i bought for spares a while back and stuck the disc over the end. not really good enough as there was alot of lateral movement in the bearing as i held it in place. then i came across the record weight i made up and had lost (found it in the kids toybox, not that i was looking for a toy to take to bits! honest!). this has a large hole on one face and a 7mm hole on the other face. sat on the bearing it drops right over it so the cog is probably an inch lower. using the same o ring it was alot better. no real movement and alot more mass to it so it will have a large flywheel effect. just hope the motor will pull it !

cressy · Post by **cressy** » Sun Aug 10, 2008 2:54 pm

found a motor pulley, again nothing special, its a brass rod coupler that happens to have the right bore, the motor does indeed pull the idler and platter! just lashed it to a 1.5v battery and we have movement!

pre65 · Post by **pre65** » Sun Aug 10, 2008 3:29 pm

Hi-when i was sorting out the motor for my belt drive turntable i purchased a 0-12v power supply.

This is not now used as Nick loaned me a dual power supply (33 + 45) so if you want to borrow it to experiment let me know.

The outputs take 4mm plugs.

cressy · Post by **cressy** » Sun Aug 10, 2008 5:34 pm

thanks for the kind offer phil but ive got one already, it has a regulated 0-18v psu and a detachable pot for the voltage control (plugs in using a quarter inch headphone jack). i have a 24v laptop psu to connect to it for mains power or a motorbike battery instead if i want to. next thing is to run up a plate to attach the motor and idler to to get the dimensions for the drive section, then have a play about with the mounting positions

Andrew · Post by **Andrew** » Sun Aug 10, 2008 7:15 pm

Coming together nicely.....should be good with that solid wood base.

-- Andrew

cressy · Post by **cressy** » Sun Aug 10, 2008 8:26 pm

done some more experimenting with the variable supply and 24v laptop supply with good results. the ratio of 1/2" pulley to idler to 11" drive face on the platter gives 0 to about 100rpm. the motor is fairly quiet and the idler does indeed give a good flywheel effect. what it does show though is that i need a properly made idler and motor pulley. the lash up was sendin vibration into the platter as the bore on the rod coupler used as a pulley is about 0.3mm too big causing about 0.6mm of " wobble. i.e the pulley is missing the idler when its drive face moves away from it due to the slight offset of the pulley to the motor shaft. the idler is offset slightly to the bearing by about half a mm too so it loses drive probably every 2nd second. the vibration is caused by the idler losing drive then hitting the platter when it regains it resulting in a ringing sound from the platter. happily the variable supply is spot on for the job and the motor has a lot of torque so should be ok too. anyone who can do some machining of an idler and pulley please help!

IslandPink · Post by **IslandPink** » Mon Aug 11, 2008 10:11 pm

Crikey
Is that inspired by the Anna Log then ?
Nice work

Mark

cressy · Post by **cressy** » Mon Aug 11, 2008 10:57 pm

im not sure where the inspiration is from i just tend to see something hanging about and think what can i do with that? the method to the madness was that the lenco has got to a point where the motor and idler interaction with the music is glaringly obvious, or the inherent problems with that deck were obvious. the rumble once exposed by the rest of the mods was doing my head in. the wow was doing my head in too. some sort of psu would cure this as it seems to be caused by the breaking and accelerating effect of the motor when the mains freq changes slightly, the rumble maybe by a replacement idler and maybe main bearing. dc off a battery would be alot better as no fluctuations to worry about and the broadcast platter and bearing so alot lass rumble to think about. i always thought that the lenco suffered because of the pressed steel chassis and this seems to have been proved by the simple damping that removed that variable completely. in turn it showed up the problems with 40 year old bearings and motors and no psu a all. this project has already shown that the quality that is needed in the engineering of the drive system far outweighs that of the plinth and spinny bits. hopefully i can overcome that.

cressy · Post by **cressy** » Tue Aug 12, 2008 10:16 pm

having had a beer fuelled faff about with the bits of the deck i have, i came across a belt in my box of bits. having lashed up the idler and motor connected with the belt it is a lot lot better. being able to add more pressure to the idlers contact with the platter the tiny offset of the drive face to the actual bearing was negated resulting in smooth drive and i was able to use the shaft below the cog to drive the belt so no need for a pulley to be made. the downside is more vibration from the motor as it needed higher revs to reach speed but even using the shaft it was easy to set the speed to 78rpm. more than enough for what i need it to do. the belt will damp the motor vibes and the 500ish gram idler will make sure they dont get to the platter. plus i can mount the idler and motor on separate pods so the motor casing vibes wont affect the idler either. i just need a shorter belt and wont have any upside down cups on the finished article!

audio-talk

and now for something completely different......

#1 and now for something completely different......

#2

#3

#4

#5

#6

#7

#8

#9

#10

#11

#12

#13

#14

#15