Member postings for Ramon Wilson

Hi Dean,

Don't beat yourself up too much - my destined 5cc pair of crankcases still sit waiting some TLC

Despite thoughts of using one for a twin shaft version it's very unlikely now that I will do anything further with them

Good to see your enthusiasm is still there, look forwards to seeing your progress on them

Best Regards - Tug

A bit of trig soon sorts that Jason but I take your point

I'm sure Jason means using a ten thou shim at one end between the stops and slip and an eleven thou at the other but to be honest Doc I think you are trying to spilt hairs here.

I can understand why you want to try but if you think about it you've already established you can get it within two thou - pretty good for the part I'd say but if you really are that fussed why not just back the topside off one thou on the closer end?

Ah Doc, you're moving into the modern age for sure - neodymium magnets indeed, whatever happened to the twist of copper wire

Nice touch and nice work

Doc,

When you machine between centres and swap end for end you should check the datum again as, unless you are certain they haven't, the centres may have slightly differing depths - that will affect the position slightly relative to the bed stop.

Any material is fine for the test bar

You may find once you've fitted that button things will improve some.

With the lathe stopped I touch the tool on the end of the workpiece, set the stop with the required slip(s)s, and lock firmly. Back the tool off slightly with the top slide and then, keeping the saddle up firmly to the stop and slip(s) and holding in place with the handwheel - with the lathe now running - bring the tool back up to just witness touch the face, taking a skim down to the centre if thought necessary.

That should see you within a thou or so given any tiny slack in the system.

If your slips are 'worn' as some of mine are and they don't wring that well I make the pile up and just lay a piece of masking tape on to keep them together until the pressure from the hand wheel takes the strain.

I have no idea Doc. I think I posted something on here in the past regarding plastic modelling distraction but it may have been on Model Engine Maker.

Re a stop button, yes it's a good idea to fit one as A, the surface is a bit hit and miss and B fitting one gives you some room to hold a slip in.

I managed to drill my saddle and glued in a hardened button - I found the right spot by turning a point on a piece of steel that fitted the stop block and used it as a centre punch.

Definitely worth doing

That's a much better finish eh Doc

Nice work on the Vulcan - do you think we ought to start a 'Plastic Distraction' thread ? There seems to be several on here who are interested.

R

Edited By Ramon Wilson on 04/09/2022 22:17:49

Ah, then best you share the book together Jason

Doc,

The likely hood of you needing to remove the crank(s) in the future is quite remote but I certainly wouldn't go for a fit that you could tap off as that will soon lead to wear when running even if pinned as you want to.

A small cutter could be used as Jason suggests but there is still the potential of dissimilar metals and the cutter going off line. Not definite but possible and if it does then you have a situation that will be difficult to disguise - why go there in the first place especially where, despite the text book diagram, there is little evidence full size.

Loctite will be more than sufficient but I always take a belt and braces approach and put a pin in as mentioned before, easily drilled out - you may recall, I had to do that to mine to change the cranks from 180 to the more norm of 90 - and easily disguised. Your call of course, just my thoughts .

Paul (Kemp). Thanks for the link, that's a beefy key way but as I see it the guide is for cutting a parallel slot on a taper - not cutting a taper in a parallel bore using the broach to achieve it.

Paul (Lousick) I don't, nor didn't, doubt your's or Jason's claim, just that to me that's not the way to use a push through broach. As you say you have to constantly relieve the pressure as the broach is pushed off the vertical. To me, though it may, and in your case did, work there is no guarantee the broach stays in contact with the guide - very likely too I agree but not certain.

As I'm sure you are only too aware machining a taper to an exact match has to be perfect, no doubt you can set your flywheel in place where you want it to go and tap the key home from the end of the shaft to locate it in position. As it stands Doc intends to machine two keys that sit in a captive slots and push the flywheel over the keys such that the tapers engage when the flywheel is in the right position.

There may be some leeway in the captive slots but I still stand by my thoughts that this is not the way to go - for a flywheel of this nature.

But then they are only my thoughts

Best everyone - now I'm off for the day to be distracted by my plastic distraction - R

Edited By Ramon Wilson on 04/09/2022 09:23:09

Edited By Ramon Wilson on 04/09/2022 09:25:12

Yes I have a very similar drawing in a book of mine. Nothing wrong with the idea but as mentioned before it's hard to find a full size example in any of the books (of engines) I have. Occasionally the odd one is keyed with a square key but most are simply shrunk on. (there's a great description of how they did that in Arnold Throp's book BTW

If you are using the cast iron cranks from Stuart there may also be the possibility the drill will run off in the softer cast iron so something to be aware of. My moneys on a pin from the major end just through the shaft - as with Jasons thought very easy to drill out if required and very easy to disguise.

Plus one for simply Loctiting the crank pins - I certainly don't bother with tapers - but have the last mil or so a tight interference fit so it tightens up as it presses home

Hello Martin,

The way a push through broach works is by an increase in height of each tooth from the bottom to the top along it's length. The bush/guide has a parallel slot in so that as the back of the broach moves down in contact the increasing height of each tooth makes subsequent deeper cuts. The depth of cut of one stroke of the broach is the increase from the smallest tooth in initial contact to the largest. The broach is pushed right through the workpiece.

If the slot is not deep enough further depth can be made by introducing shims behind the broach and repeating the process until the required depth (within the limit of the broach) is reached.

As supplied I do not know of guide bushes that feature other than parallel slots - I may be wrong but I don't think so.

Best - R

I think it's time to call it a break Jason don't you think?

Of course there are all sorts of flywheel, and consequently the mounting of too, but we are specifically talking here of a representation of a large double flywheel of several tons on a stationary engine on a shaft supported at either end. 'Horse for Courses' in other words. The flywheel on the Mc'Onie for instance has a tapered key to hold it in situ but not a tapered slot to match. As you rightly say " Maybe not right for a big mill engine"

I'm well aware that the taper is not providing the drive but the key itself - I think by now that it should have been clear that I understand that.

It the situation is as described by Doc he will have a tapered key(s) sitting in a captive slot(s) and have to place the flywheel on the shaft after the key is in place. The tapers will have to match pretty well if the wheel is to stop in the correct place laterally. I'm sorry but I simply can't see that as full size practice.

It's his choice of course, but definitely not the way I would approach the job.

This all began by Doc implying he was going to slot these components using the lathe as a slotting tool. I think I said right at the outset 'unless you have access to broaches' which like you, I happen to have, but many, if not most, don't, then the matter of accurate division on the lathe for two keyways could be an issue.

Try to cut the taper as you suggest by all means - if it works then great - it just isn't the way I was taught to use push though broaches.

Now, I really do think we have exhausted this subject and Doc certainly has enough information to do as he chooses - I think it's time we let Doc get on don't you think

Best - R

PS The slotting tool I made was a very early tool so that I could do the engraving on a Quorn. Whilst it has had little use in comparison to most accessories made over the years when it has been used it's been quickly realised it was well worth the effort put in to making it - just like the Geo Thomas rolls, little use - godsend when required.

Edited By Ramon Wilson on 03/09/2022 14:32:46

Oh I wish Doc, my days of late nights in the workshop are long over. To think, I used to machine all day then come home again and carry on in my own workshop. For many years it was in the third bedroom! but soon moved into a larger shed. At first I used to rattle around in there - space is pretty limited today for sure.

Yes I do understand it's your second model, my mistake perhaps but I was under the impression you wanted to improve on the PR. I certainly don't think it's too big a step, the 10 was a superb result for a first model and I'm sure this will be no different.

Congratulations to your son for his achievement - looks like he's well on his way to keep tabs on Dad eh? I'm no academic as you know but spent a lot of time machining - for many years nothing short of a passion but its well on the wane now. If I'm lucky I'll get that marine engine finished but I have decided that that will be my last.

Regards - R

Edited By Ramon Wilson on 03/09/2022 13:29:18

Well like I said Doc it's down to choice but if there's one thing I do understand it is time - or rather the lack of it so I well appreciate your sentiment but...

When I built my twin Vic, apart from the inlet system, I more or less followed the Stuart drawings. As my knowledge of full size machines grew it was an engine I was never satisfied with - from an aesthetic point of view that is as it certainly worked well enough, but it was always something I wished I'd followed full size practice more and put more into it.

Quite some time after I made it we had someone exhibit a really well modified and very realistic version displayed at the Forncett ME day. I have a feeling it was featured in ME but the builders name escapes me. I'm not an envious person but it reinforced my long held dissatisfaction with mine. In the end I sold it. All the engines I have made since, and no I can't match Jason on quantity, I have tried to simulate where possible the full size - I don't have that same feeling of regret on any of them and most certainly would not part with them

There's been a lot of discussion on this matter so far but no I would not advocate a grub screw drive - a key or more is correct. How it's done is down to individual choice as it's obvious from Jason, Paul and my difference of opinion

I'm not for one minute trying to force you down a path you do not want to take - that decision is yours and yours alone to make for as I have often said 'Listen to all and make your own mind how you want to proceed'.

To modify the topside as previously shown on this thread would, I agree, take time out but unlike myself age is on your side so you would have a new addition to your kit for future use. I do understand your thoughts on spending that time however - it crosses my path everyday - but all being well buying the broach will do the job and you can move on

Very best - R

Well actually they can Jason, I have seen that where a broach pulls itself into the workpiece because the broach was not being pushed in truly vertical - when that happens its a bugger to get out sometimes too.

I'm not saying your method doesn't work - you've obviously proved that to yourself for yourself but I'm not convinced from my past use of broaches. Just to be clear - are you pushing the broach right through the workpiece ?

Guys, I'm not being pedantic here but I just don't see, based on my use of push broaches, not just at home, why there is need to go to all these lengths to get a flywheel drive on a shaft, it is after all a pretty basic requirement and to be honest Doc, if you are trying to replicate a full size machine of similar attribute the flywheel would in all probability be staked not keyed - but you'd still need to slot the wheel of course.

From the outset I did say if broaches are not available then slotting is the best (only?) option. A broach is a dedicated piece of kit - not cheap for what it is and can easily be damaged/ broken. A slotting device on your lathe is far more versatile for a relatively short diversion. But that's my take - money and choice being the ever present convention.

Paul, I'll rephrase that remark , "I'm well aware that the key is not tapered on the sides" - brain fade on my part I was seeing this different to how you obviously meant.

To make a matching key tapered on the sides if you did however would require some pretty sophisticated machining of the key.

Obviously theres a big difference in being able to shape/slot the keyway than to broaching - but I'm not convinced on achieving a guaranteed taper with the latter as shown.

Machining matching tapers at any time on anything is not the easiest to achieve though not impossible but it brings me back to my early thought - make the key parallel such that it is slightly higher that required and then file a very slow taper on the top face until it just nips up as it drives home

On that note, this is taking far to much time from my plastic distraction so I'll bow out now

Good luck with it Doc however you do it

R

Well, I've read that through and I'm still not convinced by your sketch Jason or your description Paul

Forgive me for being thick but if the broach is pushed through as it is designed to do then the wide end of the broach is doing the final cutting and sizing the depth of the slot on each stroke. Cutting a taper in the guide slot is not a guarantee that the broach will follow, besides although diagrammatical, you have the broach tilted.

Paul , I'm well aware that the key is not tapered on the sides - how on earth could you broach anything if it was.

With regards to shaping I've already said that from the very beginning, and in my last post, the axis of travel defines whatever taper you desire - it's basic and easy to do by shaping on the lathe if you have the means to alter the angle of travel

This extension to the Bentley crankshaft required a key to be absolutely accurate to ensure concentricity. The picture is rather dark but you can make out the slot inside the mating taper

This shows it in place, the hole is where the tool bit ran out to clear the swarf. The tapered area between the two parts roughly in the centre is also tapered with a key though it cant be seen. The key slot is at the same taper

The mating part is slotted at the same matching angle but the drive is off the side of the key not the taper itself

So on that note "you broach how you want to" - I'll stick to what I know.

Hi guys,

Following Jason post on another thread on the subject of broaching a slot.....

I broach my flywheels to match the angle of the gib head keys, plain milled slot in the shafts and not had one fall off yet out of about 25 done that way. No grub screws used either. Before getting some broaches I planed my keyways with the lathe moving the carriage in and out with a 1thou cut per pass, tilt the flywheel in the chuck or pack on the faceplate to get the seat angle.

and Paul's comment earlier...

Now, you’re talking, you could even go the extra mile and taper the bottom of the bush slot for a “proper” tapered key

I'd appreciate it if you could explain how you do that using a push through broach in parallel bore with a parallel guide.

Despite making my comment above on possibly tapering the slot (in the guide), I got my broaches out today and tried to envisage how the broach would act with the part tilted. I guess I'm being clouded by something or missing something completely but I simply can't see how that would work in practice let alone effectively and accurately.

On my slotting head, should I want to induce a taper in the keyway (and I have to say I haven't felt need so far), then it's a simple matter of setting the slotting head to the angle required.

I'd be interested to hear how you both go about it

Best - R

Edited By Ramon Wilson on 02/09/2022 21:58:18

Edited By Ramon Wilson on 02/09/2022 21:58:47