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Member postings for John Haine

Here is a list of all the postings John Haine has made in our forums. Click on a thread name to jump to the thread.

Thread: Super 7 questions
16/10/2021 17:56:59

Regarding the link belts question, the original S7 uses I think "A" section but the big bore "Z" section which are actually smaller in width. Important to get the right ones, A section link belts on Z section pulleys slip. There are also link belts with links moulded from flexible plastic without reinforcement - I bought one of those from RDG and it was quite unsuitable, stretched like anything and slipped badly. Finished up with a Gates red belt made of some sort of fibre sections bought from RS.

Thread: Load reactors for VFDs
16/10/2021 14:33:44

I think that the motor is more likely to generate spikes itself rather than the VFD. I think that spikes will occur because of leakage inductance in the motor windings, which might overstress the VFD semis or the motor insulation, or both. Adding series inductance would surely make spikes worse as in effect it's adding leakage inductance? It might be possible to mitigate spikes with some small shunt capacitors (suppressions caps) provided you get them with a high working voltage. Before trying this do you have a 'scope to see if there are any spikes in the first place?

Thread: Reproduction ivory look hand grips
14/10/2021 13:27:19

Apparently you can pickle a peeled potato in glacial acetic acid to make a substitute. I've never tried it though.

Thread: Ball screws
13/10/2021 19:44:50

16mm overkill and will take up a lot of space.

Thread: Vfd and motor efficiency
12/10/2021 19:48:32

Martin, I think the first thing to do would be to re-wire the spindle motor from star to delta, as it sounds like at the too-low voltage the motor isn't generating its rated power. Then worry about changing the motor if you have to.

Are you really that concerned about motor efficiency? At 0.75 HP the motor will be consuming at most 1 kW when running which will cost you about 25p an hour. Any energy not going into making chips will help heat the workshop too.

Thread: Flexispeed Lathe
12/10/2021 17:17:05

The Unimat 3 is M14 x 1 and IIRC the thread and register OD are just as you measured. I may have the odd threaded collar I could let you have to try?

Thread: cutting spur gears on a mill
11/10/2021 17:06:32

Nice! And thanks for the link to the code, and Duncan thanks for generating it. I am wondering about writing a Python wizard for gears, this will be very useful to get me started I think.

Thread: SKY abandoning their satellite customers
11/10/2021 10:22:07

Round here, most premises get their phone lines overhead, the same poles are used by Openreach when they roll out fibre. Another company, County Broadband, is also rolling out rural fibre in East Anglia again mainly overhead. Where they have put in underground, for example in a nearby village, they have done a very good job of reinstating the road.

Quite a number of rural communities have benefitted from Community Fibre Partnerships that attract government funding to help the capital investment. There is also Project Gigabit just starting to roll out fibre to other rural areas.

Part of our Parish got fibre a year ago as their broadband was awful and there was another government scheme to help in areas with very low bandwidth. They can now sign up for up to 900 Mbps, and the prices are exactly the same as in other parts of the country - also can get service from any of the existing broadband providers using the Openreach network. Fibre is coming.

Thread: cutting spur gears on a mill
11/10/2021 10:11:26

Interestingly, the most common form cutters actually approximate the involute with a circle at the nominal size, and the approximation gets worse over the range. I've made an experimental version of the cutter with circular form by CNC turning, but it would be just as easy to make it a true involute. I assume that commercial form tools use the same circular approximation?

Thread: SKY abandoning their satellite customers
11/10/2021 07:18:56
Posted by David George 1 on 11/10/2021 07:12:58:

The BBC will in the near future get rid of transmitters to aerials and expect all viewers to use the broad band network instead saving billions of pounds in maintenance and renewal costs. Progress?

David

More to spend on programming? More appropriate use of spectrum. So yes, progress.

11/10/2021 07:14:31
Posted by Bill Phinn on 10/10/2021 22:21:04:

Can anyone tell me what sort of digging there has to be at a minimum to a front garden in order to lay a fibreoptic cable? I've been deterred from choosing fibreoptic until now because of the mess Virgin (or rather their contractors) wanted to make of my front garden in springtime with all my bulbs just coming into flower.

They were turned away at the scene, though wouldn't have turned up at all if Virgin had notified them, as they should have, that the customer had cancelled the contract four days before the scheduled visit.

Round here it's mainly overhead on phone poles.

10/10/2021 22:00:38

The copper network is degrading and sooner or later will need to be replaced. Fibre is significantly more reliable and cheaper both to deploy and operate. It also provides much bigger bandwidth right to the edge (i.e. your "phone" socket). Even in rural areas Openreach and some competing operators are busy rolling out fibre to premises, helped by subsidy (after all much of the copper network was built by subsidising it from expensive "long distance" calls which in actual cost terms were cheap). Radio spectrum, whether terrestrial or satellite, should be ideally kept for applications which need to be wireless. It's hard to justify still some hundreds of MHz of UHF spectrum being reserved for broadcasting when the same programmes could be delivered by the "telecoms" network alongside two-way fixed gigabit Internet. Sky's satellites were relatively cheap for them to acquire but eventually will need replacing so if a fibre fixed network is being rolled out much better for them to use it.

Thread: cutting spur gears on a mill
10/10/2021 11:03:48

Though I doubt that they made especially crude gear cutters just for Myford! However they are 14.5* PA which I think will make them look squarer. This from the late great Sir John in 2012:

"Jim,

I can't comment on the rack or it's mating pinion as I don't have any details on these but could get them if I wanted.

However as regards the screw cuting gears they are all 14 1/2 degrees PA with the exception of the first 4 on the Super 7 and like family.

The first 4 being spindle gear, the two tumblers and the gear the tumbler drives. These are 20 degrees PA.

Outboard of this they are all 14.5 degrees.

The ML7 are all 14.5 including back gear but the backgear on the S7's is special and requires a special hob as the tooth form is modified.

 

John S."

Edited By John Haine on 10/10/2021 11:05:39

Edited By John Haine on 10/10/2021 11:06:08

09/10/2021 23:03:01

Another phantom post at 2205!

Thread: Antikythera Mechanism
09/10/2021 20:45:48

Even back when Michael Wright was working on it he was using X-ray tomography for imaging the object in 3D, and I'm sure they are using more sophisticated studd now.

I haven't really been following this, but are people saying that the project written up in HJ which I linked to, one of the authors being Clickspring, which concluded that the device incorporated a lunar calendar, is wrong?

Edited By John Haine on 09/10/2021 20:46:19

Thread: Home CnC
09/10/2021 20:42:13

The Denford software is no longer supported and anyway ran on dated PC hardware and OS. You can find complete systems with a PC included on eBay but it would be a nightmare when the PC expires. But the Denford mechanics are superb, so if you could get a machine without the electronics (as I did) or were prepared to junk what comes with it it's easy to update that side of the machine with a new PC, BoB, stepper drivers etc and run a modern controller. (Ideally NOT Mach 3). May not be necessary to renew the stepper drives, as I know it's possible to get at them using the exiting board, but modern drivers are much improved.

Sir John was a great advocate of these all-in-one Chinese controllers (actually they don't have the stepper drives but those are relatively cheap) and I believe he upgraded a number of Denford machines at various universities - there's a description somewhere on this site.

I initially had a plan of making a raising block for my Novamill, but actually haven't yet had a need, especially since I found some BT30 finger collets which gives me ~50mm extra daylight at a stroke.

Thread: Mill power feed using stepper motor
08/10/2021 15:39:34

Just on the display question, as I used basically a UNO running GRBL as a pulse generator, with GRBL Controller running on an old phone as the terminal via Bluetooth, the position display comes for free. You can also set how much auto feed you want and the speed via the jog commands.

Thread: Being nice to a vise
08/10/2021 15:34:55

Good point! I would guess that the metal body is made of iron or steel selected for strength rather than hardness, so maybe possible to provide a threaded hole at the left side (if you're right-handed) for a jack screw, with a clearance hole in the jaw piece if needed.

Thread: Home CnC
08/10/2021 13:52:59

There's a Novamill at just over a grand on eBay at the moment, Mach3 converted. Has a machined riser block fitted to increase the Z height too. Otherwise working Denfords are generally pretty expensive, ~5k. I was lucky (in retrospect) to get a Novalmill without its electronics for £600, built much more modern drivers for less than 200.

You could also get a new chassis with ballscrews fiited like this one from CNC4YOU. £2648, then you'd have to fit the steppers & electronics but could probably be done for considerably less than their kit if you feel capable.

Thread: cutting spur gears on a mill
08/10/2021 08:42:41

Um, 20 dp?

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