Trilobe2.xlsb

The calculations are now all “on-sheet”
The procedure is:
1. Enter lobe height and radius and angle of first lobe to X axis.
2. Find coordinates of centres of each lobe
3. Generate 180 degree arc for each lobe.
4. Find centres of each inter-lobe arc (the intersection of a radius line through the end of one arc and the start of the next one.
5. Find radius of inter-lobe arcs (should all be the same).
6. Generate 60 degree arc between each lobe.

For the valve locations, they are not actually a constant distance apart. You find the X coordinate of the two points where the trilobe line crosses the X axis. The valve centre is then 5 (or whatever the radius is) to the left or right of each point.

To see the formulas for any point, place the cursor on the cell and press F2, all the cells referenced by the formula will be highlighted (if they are on the screen).

HTH

The Rev Dodgson said:

Trilobe2.xlsb

The calculations are now all “on-sheet”
The procedure is:
1. Enter lobe height and radius and angle of first lobe to X axis.
2. Find coordinates of centres of each lobe
3. Generate 180 degree arc for each lobe.
4. Find centres of each inter-lobe arc (the intersection of a radius line through the end of one arc and the start of the next one.
5. Find radius of inter-lobe arcs (should all be the same).
6. Generate 60 degree arc between each lobe.

For the valve locations, they are not actually a constant distance apart. You find the X coordinate of the two points where the trilobe line crosses the X axis. The valve centre is then 5 (or whatever the radius is) to the left or right of each point.

To see the formulas for any point, place the cursor on the cell and press F2, all the cells referenced by the formula will be highlighted (if they are on the screen).

HTH

Can you save this for me for later? I saw a great trilobite mosaic a fortnight ago in a footpath, and realised that a trilobite is a perfect subject for doing a mosaic of. I might try to do the same, but not yet, I have another one or two mosaic project ideas first.

Spreadsheet will remain their indefinitely:)

The Rev Dodgson said:

Spreadsheet will remain their indefinitely:)

The Russians will find it.

The Rev Dodgson said:

Spreadsheet will remain their indefinitely:)

their?

:)

mollwollfumble said:

The Rev Dodgson said:

HTH

Can you save this for me for later? I saw a great trilobite mosaic a fortnight ago in a footpath, and realised that a trilobite is a perfect subject for doing a mosaic of. I might try to do the same, but not yet, I have another one or two mosaic project ideas first.

I usedd to make trilobite chocolates. I made a silicone mould from a Silurian trilobite when I was at university. I think my (late) son sold it (as teenagers do).

sibeen said:

The Rev Dodgson said:

Spreadsheet will remain their indefinitely:)

their?

:)

Rather strangely, I didn’t see it on first viewing.

And now I can’t un-see it.

mollwollfumble said:

The Rev Dodgson said:

Trilobe2.xlsb

The calculations are now all “on-sheet”
The procedure is:
1. Enter lobe height and radius and angle of first lobe to X axis.
2. Find coordinates of centres of each lobe
3. Generate 180 degree arc for each lobe.
4. Find centres of each inter-lobe arc (the intersection of a radius line through the end of one arc and the start of the next one.
5. Find radius of inter-lobe arcs (should all be the same).
6. Generate 60 degree arc between each lobe.

For the valve locations, they are not actually a constant distance apart. You find the X coordinate of the two points where the trilobe line crosses the X axis. The valve centre is then 5 (or whatever the radius is) to the left or right of each point.

To see the formulas for any point, place the cursor on the cell and press F2, all the cells referenced by the formula will be highlighted (if they are on the screen).

HTH

Can you save this for me for later? I saw a great trilobite mosaic a fortnight ago in a footpath, and realised that a trilobite is a perfect subject for doing a mosaic of. I might try to do the same, but not yet, I have another one or two mosaic project ideas first.

Moll, you do realise that the spreadsheet isn’t about trilobites, but a three-lobed (hence “trilobe”) design SN asked about a while ago, don’t you?

The Rev Dodgson said:

Trilobe2.xlsb

The calculations are now all “on-sheet”
The procedure is:
1. Enter lobe height and radius and angle of first lobe to X axis.
2. Find coordinates of centres of each lobe
3. Generate 180 degree arc for each lobe.
4. Find centres of each inter-lobe arc (the intersection of a radius line through the end of one arc and the start of the next one.
5. Find radius of inter-lobe arcs (should all be the same).
6. Generate 60 degree arc between each lobe.

For the valve locations, they are not actually a constant distance apart. You find the X coordinate of the two points where the trilobe line crosses the X axis. The valve centre is then 5 (or whatever the radius is) to the left or right of each point.

To see the formulas for any point, place the cursor on the cell and press F2, all the cells referenced by the formula will be highlighted (if they are on the screen).

HTH

Thanks hugely, again. But what is a ‘valve?
And I think I forgot to mention something very important – The distance between the two bearings is constant, as each end has a piston on it so the two bearings are on what’s the equivalent of a conventional con-ron in a regular engine.
I had a fiddle with Solidworks and using the spline tool and a bit of fiddling I was able to get the bearings close to being in contact with the rotating tri-lobe, but not all the way around. The other problem was that whilst the piston accelerations were quite reasonable at the top’s & bottoms of the lobes, the middle region had the accelerations very high indeed. I’d guess too much. Here’s what I came up with.
I’ve also made a short video of it, I can upload that to Youtube if you like.

Valve = bearing :)

That’s even worse than writing their instead of there.

Spiny Norman said:

The Rev Dodgson said:

Trilobe2.xlsb

The calculations are now all “on-sheet”
The procedure is:
1. Enter lobe height and radius and angle of first lobe to X axis.
2. Find coordinates of centres of each lobe
3. Generate 180 degree arc for each lobe.
4. Find centres of each inter-lobe arc (the intersection of a radius line through the end of one arc and the start of the next one.
5. Find radius of inter-lobe arcs (should all be the same).
6. Generate 60 degree arc between each lobe.

For the valve locations, they are not actually a constant distance apart. You find the X coordinate of the two points where the trilobe line crosses the X axis. The valve centre is then 5 (or whatever the radius is) to the left or right of each point.

To see the formulas for any point, place the cursor on the cell and press F2, all the cells referenced by the formula will be highlighted (if they are on the screen).

HTH

Thanks hugely, again. But what is a ‘valve?
And I think I forgot to mention something very important – The distance between the two bearings is constant, as each end has a piston on it so the two bearings are on what’s the equivalent of a conventional con-ron in a regular engine.
I had a fiddle with Solidworks and using the spline tool and a bit of fiddling I was able to get the bearings close to being in contact with the rotating tri-lobe, but not all the way around. The other problem was that whilst the piston accelerations were quite reasonable at the top’s & bottoms of the lobes, the middle region had the accelerations very high indeed. I’d guess too much. Here’s what I came up with.
I’ve also made a short video of it, I can upload that to Youtube if you like.

Oh, a variation on a swashplate crankshaft.

btm said:

Moll, you do realise that the spreadsheet isn’t about trilobites, but a three-lobed (hence “trilobe”) design SN asked about a while ago, don’t you?

Oops. Thanks. Brain failure. Have a three lobed symbol.

btm said:

Moll, you do realise that the spreadsheet isn’t about trilobites, but a three-lobed (hence “trilobe”) design SN asked about a while ago, don’t you?

what a gyp

dv said:

btm said:

Moll, you do realise that the spreadsheet isn’t about trilobites, but a three-lobed (hence “trilobe”) design SN asked about a while ago, don’t you?

what a gyp

Old Australian quite racist term. Interesting conundrum. Gyp —-> Gypsie —-> Egyptian. Interestingly, not “Romani”.

:)

FWIW here’s the video of the tri-lobe contraption I came up with

Spiny Norman said:

FWIW here’s the video of the tri-lobe contraption I came up with

Cool.

Spiny Norman said:

FWIW here’s the video of the tri-lobe contraption I came up with

That seems pretty much like my spreadsheet animation (other than being 3D, with zooming in and out etc).

But that isn’t with the constraint of the two bearings having an equal distance, is it?

The Rev Dodgson said:

Spiny Norman said:

FWIW here’s the video of the tri-lobe contraption I came up with

That seems pretty much like my spreadsheet animation (other than being 3D, with zooming in and out etc).

But that isn’t with the constraint of the two bearings having an equal distance, is it?

Unfortunately not, sorry.
For various reasons I’d also like to be able to generate asymmetric lobes as that would possibly allow for more power. Attached is an example.
I may well have to do it the old-fashioned way that mathematically-illiterate engine people (like me) have used for many decades – Set the crankshaft at 0° and various parts that contact it, then turn the crank 1° at a time and mark the contact points. Repeat for the full 360°.

Spiny Norman said:

The Rev Dodgson said:

Spiny Norman said:

FWIW here’s the video of the tri-lobe contraption I came up with

That seems pretty much like my spreadsheet animation (other than being 3D, with zooming in and out etc).

But that isn’t with the constraint of the two bearings having an equal distance, is it?

Unfortunately not, sorry.
For various reasons I’d also like to be able to generate asymmetric lobes as that would possibly allow for more power. Attached is an example.
I may well have to do it the old-fashioned way that mathematically-illiterate engine people (like me) have used for many decades – Set the crankshaft at 0° and various parts that contact it, then turn the crank 1° at a time and mark the contact points. Repeat for the full 360°.

Can you explain in more detail how asymmetric lobes could allow for more power? Is this an optimisation problem?

mollwollfumble said:

Spiny Norman said:

The Rev Dodgson said:

That seems pretty much like my spreadsheet animation (other than being 3D, with zooming in and out etc).

But that isn’t with the constraint of the two bearings having an equal distance, is it?

Unfortunately not, sorry.
For various reasons I’d also like to be able to generate asymmetric lobes as that would possibly allow for more power. Attached is an example.
I may well have to do it the old-fashioned way that mathematically-illiterate engine people (like me) have used for many decades – Set the crankshaft at 0° and various parts that contact it, then turn the crank 1° at a time and mark the contact points. Repeat for the full 360°.

Can you explain in more detail how asymmetric lobes could allow for more power? Is this an optimisation problem?

There’s a couple of reasons. You can get a bit more power in a conventional engine by moving the centreline of the crankshaft a little, say 5 mm, to the side where the crankshaft is going upwards. This does increase the friction of the piston going upwards a little, but it also reduces the friction as the piston comes down on the power stroke. It’s worth a few percent increase in power.
The length of the con-rod in a conventional engine also affects the motion of the piston around the top of each stroke. Shorter rod have higher accelerations around TDC, longer rods have the piston dwelling around TDC. In nearly every situation, you want good piston dwell at TDC as at high revs the combustion pressure has more time to increase and so force the piston down the bore a bit harder and so more power, etc.
By having asymmetric lobes on that tri-lobe shape, it’s be possible to tailor the piston dwell to any degree you desire.

Swashplates.

Spiny Norman said:

The Rev Dodgson said:

Spiny Norman said:

FWIW here’s the video of the tri-lobe contraption I came up with

That seems pretty much like my spreadsheet animation (other than being 3D, with zooming in and out etc).

But that isn’t with the constraint of the two bearings having an equal distance, is it?

Unfortunately not, sorry.
For various reasons I’d also like to be able to generate asymmetric lobes as that would possibly allow for more power. Attached is an example.
I may well have to do it the old-fashioned way that mathematically-illiterate engine people (like me) have used for many decades – Set the crankshaft at 0° and various parts that contact it, then turn the crank 1° at a time and mark the contact points. Repeat for the full 360°.

That should be pretty easy with the spreadsheet approach.

I’m tied up listening to people talk about concrete at the moment, but I’ll have a look at it when I get a chance.

FWIW, this is of interest.
http://lkcl.net/engine/

Spiny Norman said:

FWIW, this is of interest.
http://lkcl.net/engine/

:)