Here is a list of all the postings Simon Williams 3 has made in our forums. Click on a thread name to jump to the thread.
Thread: Interference fit bearing sleeve |
13/07/2023 20:49:22 |
Posted by not done it yet on 13/07/2023 20:19:32:
Ep90 gear oil? Do be careful that it doesn't contain extreme pressure additives that eat yellow metals. I wasn’t aware that there was any form of oil pump in those Fairey overdrives. Are they not just splash lubricated? I had two fitted to my Series lll - one always ran very hot and its replacement was a far better unit (ran cool and drive selection was far smoother). Hopefully my comments re GL4 and GL5 oils cover this. As to the "pump" concept, the main output gear is drilled radially with small holes in the lands at the bottom of the teeth. Hence oil brought up from the sump riding the gear teeth is squished under pressure through these holes as the teeth mesh, providing lubrication to the bearing inside. Edit : Bear in mind that oil for the final drive gear is from the sump of the transfer box. In theory this oil is kept separate from that in the bottom of the overdrive so hopefully the cooling of the inside bearing is better. Edited By Simon Williams 3 on 13/07/2023 20:53:24 |
13/07/2023 20:08:22 |
Posted by Neil A on 13/07/2023 19:13:38:
I note that you say that the bush should not rotate on the shaft, but as both the shaft and the housing appear to be hardened it would be possible to just have a fully floating bush with no interference fits involved. Provision would need to be made to feed oil from the outside to the inside of the bush.
Not knowing the details of the design I do not know if such a bush would be fully retained axially. Also it depends on the actual finish in the bore where the apparent indentations are. If I remember correctly, EP oils have sulphur content which has an adverse on copper based bearings, this may make such bushes short lived, but this may be acceptable to you. Neil Neil I love it. The power of lateral thinking. The bronze can be located axially as there are snap rings both ends of the inner sleeve. Sidesteps the problem of interference fits both ways. You are also right about the issues that modern gear oils containing sulphur create in use with bronze bushings. This gear oil is known as GL5. GL4 doesn't contain sulphur derivatives and is OK in these gearboxes which have bronze synchro hubs, also for back axles with bronze crown wheels. If I've understood things correctly. Thanks as ever |
13/07/2023 18:28:37 |
My bronze bearing sleeve will occupy the space where properly the rollers and cage on the sleeve would be. I want to make it fast on the inner sleeve, and slide on the (brinelled?) surface of the inside bore of the helical gear which is lubricated via holes in the base of the gear teeth such that gear oil is squeezed into the bearing space by the meshing action of the gears. Yes, I agree that if Mr Fairey didn't need to go to the trouble and expense of providing a needle roller bearing running in close tolerance and hardened surfaces he'd have fitted a bronze bush and called it good, but these things are intended for long periods of heavy service in arduous conditions with poor maintenance. The poor maintenance might be a good fit, but my application is light duty by comparison. I'm happy with the logic that has come forward to say "don't make it a press fit, the sleeve will stretch and burst" Fair point. I'm equally happy to accept that the whole idea is barmy and won't last five minutes/5 miles/next service interval. Such is experimentation. I like the idea of freezing the splined sleeve and heating the bronze bush to assemble them together, except I don't see why the resulting hoop stress in the bronze is any different to that left by a press fit, So the gospel according to Loctite has it at the moment. I'd be grateful for your thoughts.
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13/07/2023 18:11:37 |
Well chaps, firstly thanks to all of you who have given this brain space, and replied as above. I guess I need to provide some additional information to eleaborate on my initial intentionally succinct query. The application is part of a Fairey Overdrive for a series 2a diesel Land Rover. I have several of these - the o'd that is - and I'm optimistic of making at least one complete one out of the box of bits. I bought this one recently - it's a good place to start.
In explanation, this unit is a completely mechanical gearbox which bolts into the back of the main gearbox. The helical gear is the output shaft, the input is concentric and runs on a needle roller bearing inside that lumpy looking gear. The input spline looks like this:
These are two identical input sleeves, the upper one has damaged splines and the external roller bearing is worn. The lower sleeve is new but does not have the roller bearing fitted yet. That roller bearing runs on the inner of the overdrive output gear - the big helical gear in the first picture. Or it would if the inner surface didn't look like this: I don't know if this is technically brinelling, those marks are indents in the hardened surface of the internal bore. There are several ways of getting out of jail here. The shaft is not available as a new spare part, so one is going to choose between remedial work or finding a serviceable secondhand replacement. Suffice it to say I have two of these units with the same problem. One way of tackling this is the "grind it bigger, chrome plate it and grind back to original spec" approach. I'm prepared to follow this if I can find someone who is prepared to take it on. It's outside my comfort zone by some way. Given that the differential speed between the two shafts is either zero or a maximum of about 1300 rpm,, and the bearing bore is amply lubricated, I'm interested to make a bronze plain bearing and try it. It's a very quick cheap fix, and while I'm prepared to agree it isn't in the same class of exoticness as the original needle roller bearing I can accept that risk for the potential advantage of it being within my capabilities to make. Enough for one post, I'll continue in a second shortly. |
12/07/2023 23:24:06 |
Good evening all I want to make a phosphor bronze sleeve shaped plain bearing to be a moderately heavy press fit on a 50 mm OD hardened steel shaft. The bronze sleeve will be nominally 58 mm OD so fairly thin wall, and 22 mm long. The outside surface (sliding bearing surface) is pressure lubricated with EP90 gear oil. How much interference should I be shooting for? The degree of interference must be less than that which would stretch the OD such that it will not run in its (lubricated) bore, let alone rupture the sleeve (hoop stress). Can anyone quantify the force needed to install said bush - my press will cope with about 8 - 10T. Is this adequate for a "moderately heavy" press fit? Is there an empirical force vs interference relationship? If it helps it's an experimental modification to an obsolete Land Rover overdrive gearbox, to replace an existing needle roller bearing where the outer running surface is damaged such that re-use of the roller bearing (or a new replacement) isn't going to happen. The bearing mustn't revolve on its spigot - hence the press fit - but I don't know how to quantify the tangential friction forces on the bush. If I've understood the mechanics of the original design these forces are pretty small, but that's the experimental bit! Looking forward to the knowledge as ever Rgds Simon |
Thread: Help. Myford Super 7 threads not equal gearbox chart |
09/07/2023 22:22:31 |
Matthew, thanks for letting us know we got there! One final thought to put this one to bed, and that is that it probably wasn't a coincidence that your Dad was playing tunes on the gearbox drive train. It's a well established practice and allows a wide variety of thread pitches not advertised on the gearbox top label to be achieved. Brian Wood (yes the Brian who corrected my silly error earlier with such tact and poise!) has written a book on the subject. It's title is "Gearing of Lathes for Screwcutting" published by Crowood Metalworking Guides. Amazon have copies, I believe Arc Euro have sold it as well. Quite apart from being an interesting read it's the definitive work on the science behind altering the gear train to make the lathe much more versatile. It majors on the S7 but other makes and models get a mention. Enjoy! Simon |
09/07/2023 16:04:32 |
+ 1 from me for reducing this to very first principles, as everything points to your Dad doing something "off piste" If you strap a Sharpie to the tool post you can mark out an erasable thread without cutting metal at all. Do let us know how this turns out. Rgds Simon |
09/07/2023 14:21:14 |
Have we got to the bottom of this yet? By which I mean - on the basis of this additional info from Matthew - I don't think the input gear is the only consideration. If Matthew's diagram of gear numbers is correct, there are some odd looking gear ratios in the gear train. My understanding - based on my old MK1 S7 - is that the final gear is 72 teeth, the two idlers are each 51/17 (ie 3:1 each giving a 9:1 reduction for the fine feed, a 1 : 1 straight through for the threading application) and a 24T (not 30T, thanks Brian) on the mandrel as the input gear. As I say, if Matthew's hand written sketch is correct those gears won't do what we're expecting. The 45 T gear as the first driven doesn't look right, isn't this a 30 with the 24T (mandrel gear ) compounded to it. Does this iteration of the S7 have a 45T gear on the tail end of the spindle? On my older machine the gear on the tail of the spindle is a 30 T. And having a 70 T gear driven by a 21 on the g'box input shaft doesn't look right at all. Any thoughts?
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09/07/2023 10:35:28 |
Thank you Brian, and good morning. I was hoping you would chip in with the rights of it soon. If I adjust my arithmetic with a broad smile as if nothing was ever wrong I suggest Matthew has a 20 tooth gear (24 / 1.2) on the mandrel. He's cutting more TPI so the leadscrew is running slow, hence the gear he's got driving the gear train is smaller than the one intended. Apologies for the confusion. Best rgds Simon Edit - at least I could spell the OP's name right! Edited By Simon Williams 3 on 09/07/2023 10:40:20 |
09/07/2023 09:49:15 |
1B (16) cuts 19.3 TPI error = 1.206 2B (18) cuts 21 TPI error = 1.167 8A (14) cuts 17 error = 1.214 Which says to me that the mandrel input gear is a factor of 1/1.2 smaller than designed. My recollection is that the input gear should be 30 teeth (someone confirm please?), divide by 1.2 gets you 25 teeth. So count the teeth on the first gear of the changewheel train, driven by the tumbler gears. I'm expecting it to be 25 teeth. Fix is to remove the compound gear, the outer one separates on a keyed bore, swap it for 30T. The manual explains in more detail. Now try any gearbox setting, you should find your TPI matches that shown on the label. HTH Simon
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Thread: Accurate sheet metal cutting |
28/06/2023 20:40:27 |
Fascinating, and thank you Best rgds Simon |
28/06/2023 16:13:47 |
Because we're a curious lot, I'm pretty certain that I'm not the only one who'd be interested to know what "A" system and "B" system infer. An idiot's guide would be appreciated! Rgds Simon |
Thread: Fitting a Huanyang P2 VFD to a Student 1800 |
04/06/2023 08:56:44 |
If you've got your hand in the mangle, stamp on the footbrake with all you've got. Too bad if the VFD doesn't make it. But to give it a chance, have an E Stop relay which cuts power to the VFD as a result of pressing the footbrake. There's a micro switch fitted to fulfil just this purpose with the original control circuit. The issue over whether the VFD will ramp down or loose control of the spindle doesn't matter, the brake will do it's job. One would expect the VFD to survive a power outage at full speed, so this is no worse than that. One could also devise a control scheme where this micro switch was the stop input to the VFD, but the VFD must not restart when you release the pedal. Less savage happenings - having the work shift in the chuck for example - are dealt with in the same way. It would be nice if the VFD survived so telling it to stop asap is possibly the way to do this though it does depend on the features of this particular VFD. HTH Simon |
Thread: Lathe tools |
26/05/2023 00:39:26 |
+1 for me for JB Tools |
Thread: 5mm square hole |
11/05/2023 22:12:29 |
Hi there Peter I've tried Joe Pie's method of making a square broach, it works a treat but it is fiddly. I made it to make a plastic part in the innards of a Lister sheep shear which has a 5 mm square hole in the centre to drive the flexy spring drive shaft. I made the part out of acetyl plastic. Hence I didn't harden my home made broach but it worked just fine.. To cut steel the raw broach will need hardening, which may warp it and certainly affects the surface finish. I guess one can heat treat it while in a boric acid bath a la Clickspring which will help reduce the surface finish problem. However, having it warp would make it unusable, as it will be brittle from hardening (even it it's tempered back a bit it still needs to be pretty hard) and it's absolutely vital to be able to push straight on a push broach else it will just shatter. The "necks" of the gullets are awful small (= fragile) at this size. Which leads me to comment three. I have had no luck at all trying a 1/4 inch sq broach in a normal bench vice - you can't get the force you need which is more than ever you'd imagine, and a vice won't push straight. You also need to take several bites at it to make sure the broach is setting square against the push face. I don't have an arbour press, I do it with hydraulics, but I've followed some on Youtube who have tried it with an arbour press and been surprised at the force you need. It's also only too easy not to push the broach through at right angles to the part, so the hole is skew-wiff. It's very much easier to get everything in line and acting straight if gravity is helping you rather than hindering. I recognise that 5 mm must be easier to push than 1/4 inch, but I still think you're on a hiding to nowhere trying to do this job without a hydraulic press. I recently bought a second hand 5 mm square broach on ebay. - to supersede my home made (unhardened) broach for making the spares for the sheep shearing rig. New they are about £120 a pop, I paid about half this for a secondhand one which visually looks the business but I haven't tried it yet. It looks awfully fragile! From memory the pilot hole is 5.3 mm, so you end up with a square in a circle - or a circle with corners if you like. If this is of use to you PM me and we'll work out something. No promises of success - if I break the broach then I can't replace it. Did I mention it looks awfully fragile? But it's gotta be better than filing each one individually. What tolerance on orientation of the square have you got to keep? The broach cuts the square corners dead to size, but there is the question of the slightly oversize pilot hole which may be problematical. If you'd like to take this further leave a message here to say there is a pm to find - I check the forum most days but only log on if I need to, so I may miss the little black envelope icon. HTH Simon |
Thread: Myford Super 7 - electrics/motor |
08/05/2023 12:55:40 |
I fitted a very similar looking motor carrying an AEI Houston label to mine, three phase with a VSD but 2 pole to rev the old girl up a bit. Very successful, until a small but persistent spiral of swarf managed to make its way through the ventilation hole next to the terminal box. Sparken blitzen mit ausgepouf. It needs its ventilation but you might like to cover the hole. HTH Simon PS I wouldn't question 1/4 HP - yet. Plenty of umph to get into trouble, run it and learn its limits for a while. |
Thread: Myford Lathes |
29/04/2023 14:09:57 |
Message for John Broughton, just to inform the discussion : Does your S7 have a quick change gearbox fitted? If yes, then the possibilities identified in the thread to which JohnF refers are available to you. Post is above timed 09.10.04 HTH Simon |
Thread: solvent for tyre valve |
29/04/2023 13:51:57 |
If you go and chat up a friendly commercial tyre fitter, the valve extender they use to bring the inner valve on dual wheels out to the side where the driver can reach to check/inflate would be a good place to start. It's a male thread with the schrader valve in one end, the other end is a corresponding female thread. There's a bit up the middle to depress the tyre valve stem. I've got a couple here made from brass, I'm sure a suitable adaptor could be made with a bit of soft soldering. I've had some schrader to 1/8 BSP fittings in the past, I've just been to the shed to see if they are where I thought they were. No such luck. But if you're stuck leave a message here and I'll have another rummage. HTH Simon |
Thread: Centering a bore on the lathe |
11/04/2023 21:47:10 |
John McCulla Where abouts are you?. If in sensible reach of West Glos (nearly S Wales) you're welcome to borrow a finger style indicator, or I can bore the hole true for you assuming the material isn't too exotic. If some help is of interest to you send me a PM and we can sort something out. I'm sure you realise you're trying to do something quite difficult/strenuous! HTH Simon PS I've got a big tap wrench too. I try and keep it in a secret drawer with the shovel. It needs a big packet of chocolate biscuits before it'll show itself. |
Thread: Help, please, selecting some Electronic Components |
16/03/2023 22:43:32 |
... and that 0.1 uF capacitor shorting the input pulse train to ground needs the attention of a pair of snippers. There's also something a bit odd about having a decoupling capacitor (drawn as an electrolytic) connected reverse polarity across the op amp supply. So I wouldn't take the strictures of component selection too seriously. R1 could be metal film, they're inherently non inductive and cheap and readily available, also the 3300uf capacitor will have some ESR and inductance at high frequency but that's why it's got a 1 uF capacitor in parallel. I'd go tantalum rather than electrolytic for the 3300 uF though I doubt if it's critical what value this is, and little bead ceramic capacitors for the others. Don't feel I can offer an opinion on the LED, this seems to be more about the precise definition of the light pulse in duration and spectral purity (can white light have spectral purity?) more than its electrical properties. HTH, hopefully Joseph Noci will lend us his expertise ere long. Rgds Simon |
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