Gearless Hypocycloid Engine

[Ken I]

I was in contemplative mood and playing with my hypocycloid engine and wondering what else I might - as an engineer - accomplish with its strange motions.
See prior Hypocycloid :-

Hypocycloidal Engine

It suddenly dawned on me that any point on the PCD of the pinion gear will describe a straight line - but in a different direction than the piston stroke.

Therefore the motor could be made to work using a series of pins or rollers running in a series of straight grooves.

This I thought, might be handy for those guys who perhaps wanted to build a hypocycloid but were put off by the need to make a decently accurate annulus and pinion gear set. Particularly as there is no easy way to fix it if runs tight or binds up.

The pin and groove method I am suggesting can be readily relieved as much as is required to get it to run,

This is the GA

This is the principal difference between this and my prior Hypocycloid.

The left hand images are of the prior annulus gearset and to the right the "gearless" version.

Thanks to the ever helpful efforts and 3D animation wizardry provided by JonMCC69 the following video shows it demonstrated as a feasible model.



John's wonderful animation also shows off the action of the "D" valve and its timing.

Caution: Whilst I have provided the plans below, I have not yet built this model (but I have started).

There is an A0 pdf print and the zip file contains an ACAD.dwg file.

Regards, Ken I

 

[Ken I]

Like I said - I have started :-

Some decorative bits first just to warm up.

Regards, Ken I

 

[Jasonb]

Not unlike the Rectilinear and Cross engines by Anthony Mount, just a bit more compact and using pins rather than sliders which only need the slots at 90deg not 45.

 

[Ken I]

Jason, I have seen that cross mechanism and never realized the relationship with the Hypocycloid until now.
I considered using just two pins (you can pretty much use as many as you like) but thought that it would self lock.
Silly me.
Regards, Ken

 

[Ken I]

I can't believe its 2+ months since I started this project - but I have been rather busy designing for my business - can't have fun all the time.

I have in the interim built the cylinder assembly :-

Since this is the same as what I posted under my previous hypocycloid, I saw no point in boring you with the details.

I am busy with the crank and pinwheel assembly (which is different than prior) and I will post on that shortly.

Regards, Ken

 

[johnmcc69]

It's looking real good Ken, glad to see you back on it!
Good to hear you're keeping busy at work as well.

John

 

[Ken I]

John, Thanks - I have just trial assembled the crank assembly and will post a video - eureka it works (at least so far).

I never posted on how I made the decorative columns - so in case anyone is interested, here it is :-

Making The Decorative Bits.

Whilst the columns and spacers are simply decorative (apart from the length), I found turning the profiles with a radius turning attachment to be an exercise in futility.

So I took a 3/32” part-off blade and hand sharpened it to a ±1.2mm radius and co-ordinate turned the profile, plunging to depth at 0.5mm steps vis :-

The chamfers on the end rads were similarly "rounded" by hand.

Whilst you could calculate these co-ordinates, it was simpler to do it in ACAD.

The resulting “ploughed field” finish was then hand finished with a file, emery paper and a polish against a mop.

The polishing was done before final part-off so it was still attached to the stock bar so you have something to hold onto for the polishing operation.

Clear lacquer spray paint applied to retain polish.

Regards, Ken

 

[Ken I]

O.K. here's the partially assembled first try fit up video.

It starts with me turning the Ø6 shaft between my fingers which shows it turns freely and then a super slowmo using a cordless drill for more consistency.

Regards, Ken

 

[Ken I]

Making The Flywheel.

I thought I would post on making the flywheel which is something I did not do on my prior Hypocycloid post and was asked about it - so I documented the making of this one.
I made a change from the earlier version in that I changed the design of the spokes from plain rods to column shaped spokes for improved aesthetics,

Start by turning the outer rim :-

In this case I made it from cast hollow bronze stock.
Finish the bore but leave the OD and width oversize by 0.5mm for final clean up later.

Incredibly brave or stupid (take your pick) parting off so far from the chuck - worked fine - my lathe would never have been able to do this with its original drive - It was just simply not powerful enough - see uprate post :-

Single Phase To Three Phase Rewind - Lathe Uprate

Next: Mount true on my small 4-jaw on the lathe which also fits my rotary table on my minimill.

Left: Mounted (and clocked true) in the 4-Jaw on the Rotary Table in the Minimill – note the first hole aligns with a jaw which I left to last as this jaw has to be removed to clear final reamed size.
Right: Jaw removed for final hole only – I could spot drill Ø6 but the finished size of Ø8 interfered with the jaw. There is no way to arrange it without having at least one jaw interfere with the drilling (I checked on Autocad just to be sure before I started).

Next: Hub & Spokes.

Top Left :- Turn Center Boss.
Top Right :- Transferred to RT on Minimill for spoke and grubscrew holes.
Bottom Left :- Making the spokes.
Bottom Right :- Fit M3 studs – check that all spokes screw down fully – you don’t want to have one dead-length on you later.

Drill rod through the bore is to check that the centreline reference is dead true for following operations - particularly the final truing up.

Top Left :- Trial fit dry (no locktite) – Note: Spokes have been polished.
Top Right :- Check Run-Out – persuade with a soft hammer if out.
Dismantle and apply locktite – reassemble and repeat alignment check.
Bottom Left :- Apply heat – fairly large flame - rotate lathe at slow speed.
Bottom Right :- Apply solder when rim is up to temperature.

Note: The rim is not red hot – that’s just patina and some reflections off the red plastic of the roll of solder (bottom right). (Whilst it looks red hot, this picture was taken with it cold.)

If you heat it quickly enough – not much heat gets through to the boss – maybe 120°C which will soften but not degrade the locktite.

As soon as you have solder wicked into all the joints, run the lathe slowly and blow cool with compressed air.

Note: Polish the internal surfaces and spokes before assembly – otherwise its going to be a lot of hard work later.

Solder runs on the outer surface of the rim are going to be machined off - just don't get any on the inside of the rim.

The spokes are relieved near the outer edge of the rim but close fitting near the inside of the rim to prevent solder wicking through to the inside surface which you have already polished.
After cooling a final clean up of O.D. and sides of the rim and emery paper - pre-polish.

Not shown - the wheel turned around and mounted on a sacrificial arbor (turned from an old bolt) for the machining of the reverse side of the boss.

After polishing I clear lacquer coated it to preserve the polish.

Tip: When spray painting a bare metal surface - and particularly a highly polished one - the paint tends to run the instant it "glazes" - the colder the temperature - the worse the problem.
So I typically warm the part up to 50-60°C with a hot air gun prior to painting - this helps flash off the solvents fast enough to more easily get a glaze without runs.

Regards, Ken

 

[werowance]

thats a really nice flywheel. question on the locktight. doesnt it prevent the solder from sticking? or were you just carefull to not get any locktight where the solder was going?

 

[Ken I]

I didn't use solder at that end instead I am relying on the locktite - I've spun it to 5000rpm and it doesn't come apart.

However, if You wanted to solder them I would recommend drilling axial holes down to the now threaded or stubshaft ends - assemble the whole flywheel.

Then lay it on its back and heat the hub boss until you can solder down the (now vertical) holes - fill to the top or plug later to clean up.

Let it cool down and mount it back in the lathe for soldering the outer ends as per above.

In fact now that I think about it you could do it like this :-

Now you can do both ends flat on its back on a firebrick instead of your lathe - the only witness marks will be the Ø2 soldering holes which are at the back and when polished and lacquered are barely noticeable.

Regards, Ken

 

[werowance]

that link doesnt load

 

[Richard Hed]

Making The Flywheel.

I thought I would post on making the flywheel which is something I did not do on my prior Hypocycloid post and was asked about it - so I documented the making of this one.
I made a change from the earlier version in that I changed the design of the spokes from plain rods to column shaped spokes for improved aesthetics,
View attachment 124388
Start by turning the outer rim :-

View attachment 124393
In this case I made it from cast hollow bronze stock.
Finish the bore but leave the OD and width oversize by 0.5mm for final clean up later.

Incredibly brave or stupid (take your pick) parting off so far from the chuck - worked fine - my lathe would never have been able to do this with its original drive - It was just simply not powerful enough - see uprate post :-

Single Phase To Three Phase Rewind - Lathe Uprate

Next: Mount true on my small 4-jaw on the lathe which also fits my rotary table on my minimill.
View attachment 124389
Left: Mounted (and clocked true) in the 4-Jaw on the Rotary Table in the Minimill – note the first hole aligns with a jaw which I left to last as this jaw has to be removed to clear final reamed size.
Right: Jaw removed for final hole only – I could spot drill Ø6 but the finished size of Ø8 interfered with the jaw. There is no way to arrange it without having at least one jaw interfere with the drilling (I checked on Autocad just to be sure before I started).

Next: Hub & Spokes.
View attachment 124390
Top Left :- Turn Center Boss.
Top Right :- Transferred to RT on Minimill for spoke and grubscrew holes.
Bottom Left :- Making the spokes.
Bottom Right :- Fit M3 studs – check that all spokes screw down fully – you don’t want to have one dead-length on you later.

Drill rod through the bore is to check that the centreline reference is dead true for following operations - particularly the final truing up.

View attachment 124391
Top Left :- Trial fit dry (no locktite) – Note: Spokes have been polished.
Top Right :- Check Run-Out – persuade with a soft hammer if out.
Dismantle and apply locktite – reassemble and repeat alignment check.
Bottom Left :- Apply heat – fairly large flame - rotate lathe at slow speed.
Bottom Right :- Apply solder when rim is up to temperature.

Note: The rim is not red hot – that’s just patina and some reflections off the red plastic of the roll of solder (bottom right). (Whilst it looks red hot, this picture was taken with it cold.)

If you heat it quickly enough – not much heat gets through to the boss – maybe 120°C which will soften but not degrade the locktite.

As soon as you have solder wicked into all the joints, run the lathe slowly and blow cool with compressed air.

Note: Polish the internal surfaces and spokes before assembly – otherwise its going to be a lot of hard work later.

View attachment 124392
Solder runs on the outer surface of the rim are going to be machined off - just don't get any on the inside of the rim.

The spokes are relieved near the outer edge of the rim but close fitting near the inside of the rim to prevent solder wicking through to the inside surface which you have already polished.
After cooling a final clean up of O.D. and sides of the rim and emery paper - pre-polish.

Not shown - the wheel turned around and mounted on a sacrificial arbor (turned from an old bolt) for the machining of the reverse side of the boss.

After polishing I clear lacquer coated it to preserve the polish.

Tip: When spray painting a bare metal surface - and particularly a highly polished one - the paint tends to run the instant it "glazes" - the colder the temperature - the worse the problem.
So I typically warm the part up to 50-60°C with a hot air gun prior to painting - this helps flash off the solvents fast enough to more easily get a glaze without runs.

Regards, Ken

THAT is truly the COOLEST flywheel I have EVER seen! Thanx for showing that.

 

[Ken I]

Making The Pinwheel. (Pinion Wheel)

Top Left :- Turning blank for pinwheel and crank flange in my small 4-Jaw.
Top Right :- 4-Jaw moved to rotary table / minimill – clocking true.
Bottom Left :- Drilling and reaming pin holes and clearance scallops.
Bottom Right :- Back to lathe for part-off.

The intention was to hacksaw it off in the minimill and continue with the crank flange.
However, I had made a mistake – and then continued to make further mistakes.
The pinwheel flange was supposed to be Ø34 but for some strange reason I had turned it (very precisely) to Ø36.0.
I found the center calculating off Ø34 so my center was obviously off by 1mm – so I would have to take it back to the lathe to correct the OD (and so I might as well part if off then) – but this meant re-clocking on the minimill when returning the crank flange (which I was trying to avoid).

Worse, I then compounded the error by merely shifting my center by 1.0mm on the dials. This is a mistake as I had datumed 17mm off-center and so my edge finder was not on center – thus introducing a 0.0244mm error – compounding in X & Y planes to 0.0345 off-center which in turn caused my pitch circle diameter to come out undersized.

It was meant to be Ø24.00 so (theoretically) it would have come out Ø23.931 because of this error – it actually came out at Ø23.95 – not that big a deal – but for accuracy’s sake it must be the same as the crank “throw” – so I’ll accommodate that error when making the crank.

Lesson: Don’t bodge a set-up error – go back to the beginning and do it right !

Riveting the pins to the pinwheel :-

Top Left :- Showing riveted heads & female riveting snap made from a scrap bolt.
Top Right :- Pinwheel assembly – the longer one is for the conrod / bigend.
Bottom Left :- 2nd Op. rig – drive pin fitted before turning.
Bottom Right :- 2nd Op. Facing on lathe.

You can always silver solder the pins into the pinwheel – I just like rivets.

I left the pinwheel flange 0.1mm oversize on thickness so that it would clean-up / remove “carpenters pennies” and other general dings and pukas from the riveting.

Building this pinwheel and the crank (next post) I made far too many mistakes but fortunately got away without making any scrap.

Note to self: Measure twice cut once - you know that dammit !

Regards, Ken

 

[Richard Hed]

Making The Pinwheel. (Pinion Wheel)

View attachment 124434

Top Left :- Turning blank for pinwheel and crank flange in my small 4-Jaw.
Top Right :- 4-Jaw moved to rotary table / minimill – clocking true.
Bottom Left :- Drilling and reaming pin holes and clearance scallops.
Bottom Right :- Back to lathe for part-off.

The intention was to hacksaw it off in the minimill and continue with the crank flange.
However, I had made a mistake – and then continued to make further mistakes.
The pinwheel flange was supposed to be Ø34 but for some strange reason I had turned it (very precisely) to Ø36.0.
I found the center calculating off Ø34 so my center was obviously off by 1mm – so I would have to take it back to the lathe to correct the OD (and so I might as well part if off then) – but this meant re-clocking on the minimill when returning the crank flange (which I was trying to avoid).

Worse, I then compounded the error by merely shifting my center by 1.0mm on the dials. This is a mistake as I had datumed 17mm off-center and so my edge finder was not on center – thus introducing a 0.0244mm error – compounding in X & Y planes to 0.0345 off-center which in turn caused my pitch circle diameter to come out undersized.

It was meant to be Ø24.00 so (theoretically) it would have come out Ø23.931 because of this error – it actually came out at Ø23.95 – not that big a deal – but for accuracy’s sake it must be the same as the crank “throw” – so I’ll accommodate that error when making the crank.

Lesson: Don’t bodge a set-up error – go back to the beginning and do it right !

Riveting the pins to the pinwheel :-

View attachment 124435

Top Left :- Showing riveted heads & female riveting snap made from a scrap bolt.
Top Right :- Pinwheel assembly – the longer one is for the conrod / bigend.
Bottom Left :- 2nd Op. rig – drive pin fitted before turning.
Bottom Right :- 2nd Op. Facing on lathe.

You can always silver solder the pins into the pinwheel – I just like rivets.

I left the pinwheel flange 0.1mm oversize on thickness so that it would clean-up / remove “carpenters pennies” and other general dings and pukas from the riveting.

Building this pinwheel and the crank (next post) I made far too many mistakes but fortunately got away without making any scrap.

Note to self: Measure twice cut one - you know that dammit !

Regards, Ken

You are a lot better at it than me, I have to measure 13 times then botch the cut anyway.

 

[Ken I]

Making The Crank.

Top Left :- 4-Jaw back on the rotary table / minimill – clocking true (again).
Top Right :- Milling the big-end hole & webs.
Bottom Left :- Milling reference flats.
Bottom Right :- Back to lathe for final turning & valve gear eccentric.

Once again I made an error – see top left photos – I should have clocked the 4 jaws “square” to the X-Y plane for subsequent machining of the valvegear eccentric – which will require this reference.

Damnbugger…..Not a train smash but an annoyance with myself.

Lower Left photo – the fix - removing 4 jaws, one at a time so I can mill reference flats for next operation reference.

Given the error in the pinwheel, I decided against boring the recesses for the big end ballbearings and opted instead for a straight hole with the bearings mounted into a turned bush cassette – which can be soft soldered or locktited into place.

This would allow me to make an eccentric bush to correct any “throw” errors that might cause binding if so required.

As it turns out I machined the throw to 24.95mm to match the pinwheel and it worked without any problems.

Back to the lathe for final turning of the backside and the valvegear eccentric :-

Left :- Since I had to remount relative to the flats, I had to re-clock the center true. Then after turning the concentric bits, I pushed the part 1.75mm off center for the 3.5mm valvegear throw.

To get this accurate, I used the clock gauge as a fiduciary gauge to zero and moved the cross slide 3.5mm to check the opposite side. (You can see the offset in the opposing chuck jaws.)

I stopped at 3.55mm as there is always going to be some play, so a touch more than theoretical is fine.

I set the eccentric so the engine will run clockwise. (Prior Hypocycloid ran anti-clockwise.)

Right :- Finished prior to part-off - the 60° chamfer from the centredrill (too deep) is also a mistake – it should have been square.

So I ended up making a small ring added to the crank pin to fill that gap – ***** !

You can see the ring in the assembly photo above.

I also riveted the crank axle pin which could also be silver soldered.

The ballbearing cassette for the pinwheel axle is locktited in place.

Like I said earlier - too many mistakes but managed to work around them all without making scrap.

Nearly finished - maybe get it going over the weekend.

Next: Making the annulus plate.

Regards, Ken

 

[Ken I]

Making The Annulus Plate & Footplate.

I had the blanks waterjet cut but under/over-sized where it counts.
The Footplate is aluminium and the anulus plate stainless steel.

Top Left :- 4-Jaw being used to align the parts for drilling & bolting.
Top Right :- Clocking for the same values in X & Y for best approximation of center from the OD.
Bottom Left :- Mounted in the small 4-Jaw for boring bearing shoulder diameter. This becomes the reference for all subsequent machining operations.
Bottom Right :- 4-Jaw mounted to RT and clocked true to bore.

Note washers between the two parts for clearance when milling the slots to clear the footplate beneath it.

Next:-

Top Left :- Setting RT true to Y plane before finish machining slots.
Top Right :- Machining slots with a Ø6 slot drill.
Bottom Left :- Cleaning up the mounting surfaces during the same set up to ensure parallelism.
Bottom Right :- Anulus plate removed by unbolting, 4-Jaw returned to lathe to bore ballbearing diameters either side – using bore as reference. (The first side being true from prior – although I did check and it needed a few microns tweaking only.)

When aligning the RT I stopped at the nearest minute – which was 32°21’ – with that locked down I machined the grooves and mounting surfaces = Y Plane – followed by the X Plane.

Then you obviously rotate the RT 45° (in this case to 77°21’) to machine the other pair of grooves in the X & Y planes as before.

The slot throws end at 24.5mm from center = 0.5mm longer than the crank throw for some clearance.

I milled using a Ø6.0 slot drill which I had previously checked before use produced a Ø5.9 slot – so I had to work back and forth from datum to enlarge the slot.

I finished at Ø6.10 which seemed to work well as sufficient clearance over the Ø6.0 pins. When I did the first trial assembly it turned over easily with just a couple of minute tight spots that hopefully will wear in during the final run-in.

Crank Assembly Drawing.

Cross-section of the crank and annulus assembly.

Regards, Ken

 

[Ken I]

Making The Baseplate.

Nothing much to show here other than the circular (machine) polishing :-

I used a machined wooden dowel faced with a 3mm thick leather pad – glued on with superglue.

Choose a convenient size and pitch and work to a pattern.

In this case Ø16 @ 9mm pitch (my minimill’s leadscrew is 1.5mm) – I first ran down the middle – then offset 9mm from row to row and 4.5mm offset of the pitching on each following row – starting each row from the same end – repeat until your arm falls off. Then work outward on the other side mirror image.

Each whorl requires 3 x 1 second dobs (up and down three times to let the "fluid" in and out) at moderate pressure at ±1000 rpm.

Last time I used coarse valve grinding paste, this time I made my own using #120 grit carborundum mixed with Rocol cutting fluid.

If you have a local waterjet cutter they use garnet powder by the ton and throw away the used stuff - waterjet cutters also have all sorts of wonderful scrap they will sell for scrap value or give it to you if you are a customer.

Tip: Take one of your model engines through to your local machine shop, carpentry shop, waterjet shop, laser cutting shop etc. etc. make contact with the owner or ops manager who will generally be quite happy to let you have offcut odds and sods. I always make a point of returning with the finished model to show them where their "donation" ended up.

Making The Wooden Base.

When machining use a piece of support scrap to mill into - to support the offside grain - otherwise it will splinter.

Same goes for routing the moulding - so do the cross grain cuts first.
Stained + lacquer spray
Regards, Ken

 

[Ken I]

Right - I said I'd get it running over the weekend and I did :-

The static photo shows it in the foreground my prior geared hypocycloid engine in the background.
Running tight and sounding like a bucket of bolts (some of the noise is the compressor in the background).
In the slow-mo of the valve gear you can see the scollops in the pinwheel dodging around the columns separating the anulus plate from the footplate.
Running metal to metal, no sealant or gland packings so it leaks like a sieve.
I haven't fitted the faux wood barrel and will only do so once I have finessed all the tight spots and got it running to my satisfaction.
Ah well - it does run at least.
Regards, Ken

 

[vederstein]

A runner is a win!