An attempt at Linear Tracking

[ian]

Squiffything posted a link to his linear tracking tonearm on DIY Audio I foolishly read this and also ChrisG139's build. Inspired by their enthusiasm I thought I'd give it a go.  It's no where near complete yet but here's where I've got so far.

[ZZMoko]

Looks great how does slide is it like Vics Trans Fi arm on air?

[decca4]

Squiffything posted a link to his linear tracking tonearm on DIY Audio I foolishly read this and also ChrisG139's build. Inspired by their enthusiasm I thought I'd give it a go.  It's no where near complete yet but here's where I've got so far.

Not that I understand how this is supposed to work but I will follow it with great interest. Good luck Ian!

[Squiffything]

WHERE DID YOU GET ALL THAT GOOD STUFF FROM?!!

I have to make do with a torch some scrap wood and some knitting needles 

Ian once again you make a very professional looking piece of kit. Hope it works out. One tip keep the wiring light and flexible my mouse wire is too stiff and prohibits the smooth movement. I'll get around to rewiring it one day

[ian]

Sorry, I meant to preview not publish .............

As with Chris and Squiffy's builds it has a track on which two ball bearings run.  They were adamant that this works so, as I said, I thought I'd give it a go.  Surprisingly it runs very smoothly indeed.  The "track" is some 20X20mm V groove stuff available online, sites that deal with robotics and building 3D printers are a good source.  Given I already had the milling jig I thought this would be a useful way of adjusting the XY axis of the tonearm to get it just right.  With T nuts it's really just like a mechano kit. .

Not so easy is mounting it on an actual turntable - getting it properly aligned so the cartridge will track properly but after a bit of fiddling here it is on Stanley.



There are a few things wrong with this but it is work in progress.
1. The angle brackets holding the jig down are too weak so there's a bit of movement there - not a difficult problem to solve.
2. The top rail that the arm wand will be hung from is the same 20X20mm profile as the supporting rail but I think the centre of gravity is too high so it is inherently unstable.  I've found a supplier who does a 10X20 profile so I'm just waiting for this to be delivered.

Mounting it on Stanley does give me the chance to work out how long the arm wand should be so that is the next stage.  The wand comes from a cheapish tonearm that I got from Malcolm in a swap - I've removed the horizontal bearing and the original headshell which of course was angled for a pivoting tonearm.  Fortunately the Sumiko headshell - with its terminal removed - is a perfect fit so this can be tightened in place once I've worked out the right length.  Short seems to be good as the aim is to make this and its carriage as light as possible given the stylus has to move the whole thing along the track.

Here's the link to the original DIY Audio thread.

http://www.diyaudio.com/forums/analogue-source/252667-my-linear-tracker-new-variation-perhaps.html

[ian]

WHERE DID YOU GET ALL THAT GOOD STUFF FROM?!!

I have to make do with a torch some scrap wood and some knitting needles 

Ian once again you make a very professional looking piece of kit. Hope it works out. One tip keep the wiring light and flexible my mouse wire is too stiff and prohibits the smooth movement. I'll get around to rewiring it one day

Wow, I didn't expect so many quick replies while I was still preparing the basic information!

Squiffs, see previous post - Total spend so far has been £26 for the bearings, aluminium etc - the jig I already had.  Regarding wire I've got some of Vic's Litz stuff which should be just the job.

Cheers, and thanks for the inspiration

[ropie]

Some people can just get things done..   Good work, Ian!

[ian]

OK, just hacked the tonearm wand to what I hope is the right length.



You can just see that the Sumiko headshell has a hex bolt to tighten it on the wire plug thingy so it's an easy job to pop this out and put the headshell on this tonearm.  The square behind is one of two delrin things obtained from a robotics site that I'll secure to the wand which will then hang off the top rail.

As I have no engineering skills whatsoever everything has to be premade or simple to adapt

Cricket's started so no more messing for a while.

[Squiffything]

Ian is the triangle support bracket going to foul the arm at the outermost edge of the record?

It does look very good on Stanley. Both arm and TT have an industrial look to them. My knitting needle solution is a little bit precarious in setting up and I can't tell you how many times the ball bearings fell off and dropped down the back of the stereo setup. Once setup however the weight of the arm was enough to hold it all steady and it played well. As I mentioned the stiffness of the mouse wires would snag it up and hinder the smooth movement every now and then and it was always one thing that I intend to improve, but the glide of the arm using the method always seemed to be very smooth.

Chris' system I felt was a much more refined and elegant solution than my BIY job (Bodge)

[Squiffything]

.....Cricket's started so no more messing for a while.

Pffft Cricket.

You just carry on that man, stop for thirty seconds while they bowl a ball then go for another five mins. Stop again for another bowl and then more TT time. Keep on like this for three hours and then crack on for two hours whilst they have tea/lunch/afternoon tea/dinner. You can get a whole turntable built while watching cricket!

[ian]

Hi Squiffs,
One of things about bodging (that's me too!) is you have to take into account simple problems like you say.  The triangle support is flush with the rail so the ball bearings lift the top rail sufficient to move over it.  The rail itself is set so the top rail can pass past the edge of the jig.  I used Chris's dimensions for the length of the rails 340mm for bottom and 180mm for top and this seems to give plenty of travel across the record surface.  One of the nice things about the V groove profile is that they sell end caps which stop the balls rolling off

Re the cricket - what you say is of course true but I'm now at the point where I need the lower profile top rail so things are naturally coming to a temporary stop.

Speaking of waiting for things,  I've also ordered this micrometer microscope stage from China.



It's smaller than the milling jig and relatively cheap (£12.55) but whether it is up to the job remains to be seen.  If it is it will be a neat way of fine adjusting the cartridge position.

[ChrisS]

the aim is to make this and its carriage as light as possible given the stylus has to move the whole thing along the track.

Is it preferable to use a relatively low compliance pickup for that reason?

[ian]

Is it preferable to use a relatively low compliance pickup for that reason?

To be honest I'm not at all sure.  Some things I've read suggest the opposite which seems counter-intuitive.  I'm sure there are more experienced users of linear trackers who can give you a better answer.

[funkpig]

This is brilliant stuff Ian.

Forget Scrap Heap Challenge, I think they should start a new series just for you called Ebay Challenge - you'd win hands down. 

[kffern]

Great to see this is being tried here. i like your choice of materials.
Having messed about with this and followed a lot I'd say your traveling bar might be a bit too heavy.
Maybe cutting it in half horizontally or using an right angle section? Will be following this with interest.

I have been using the 4 bearing on single rod version for a couple of years now and working on a twin bearing 2 rod version but got diverted on other things. It can be frustrating at times and I'd recommend using an inexpensive MM for the experimenting.
Not the sort of arm to be using after a couple of single malts!!
My first version with steel bar below. I now use a glass rod which works better but still detect a bit of coarseness towards the end of an LP.
otherwise the feeling of rightness and solidness of the bass is amazing. Current version has a nicer aluminum support and a few small improvements. Look for good tonearm wire. I use wire from transfi.

Regards,
Kevan