[help] improving a tiny V12 engine

[Divitis]

Hello fellow builders,

I'm turning to you for help with improving the V12 engine that I designed for my ongoing 1:8 car moc.

 

 

As you can see, it sits in a tiny space just above a 5+R manual gearbox - which I'd be happy to further show as soon as I find the time - and it kind of works, however the firing order is terrible and the last piston only moves half the time. 

This happens because this is the best driveshaft I could fit into what little space I have left (the hood currently nearly touches the engine bracing).

  

Now, does anyone have an idea for building a driveshaft that will allow pistons to move in a more realistic way? 

Here's the Stud.io file for you to get started. 

I managed to be accurate with the gearbox ratios and orienting the engine 60 degrees (it annoys me so much that Lego still using the connector block even in 1:8 cars) but this engine thing is driving me nuts.

Please save me!

Edited April 10, 2024 by Divitis

[Jurss]

New parts from kawasaki?

But did You tried to use full stud lenght axles, 2L halfbeams.

[Divitis]

Thanks for chiming in, Jurss. I would love to be able to use the Kawasaki pieces.

Unfortunately the cam piece is 3L in diameter and I only have 2L available (because of the 28t gear)

[Thirdwigg]

Why not just use the standard Technic engine crankshaft with 1L lift arms on the axles to lift all the pistons. It fits within 2L.

[Divitis]

  On 4/10/2024 at 12:40 PM, Thirdwigg said:

Why not just use the standard Technic engine crankshaft with 1L lift arms on the axles to lift all the pistons. It fits within 2L.

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Thanks for the idea! I managed to put this together, that fits the space.

Unfortunately 2L pistons fall down (you can see one in the photo) and 3l ones would hit the hood.

I also tried with custom made pistons using plates to extend a 2L bar, but it is too loose a fit into the technic hole and so it looses orientation and ultimately gets stuck.

[MinusAndy]

Just a thought but could you put the crankshaft elsewhere and run the pistons via rockers? 
 

[Stereo]

Would it be ok to space the pistons out more?  You could alternate 1x1 bricks and 1x2 bricks with 1 hole so they're 1.5 studs apart, and then use entirely the crankshaft "Type 1" inserted with all the axles in a straight line, so the pistons only rise 1/2 stud, don't drop 1/2 stud.

[Divitis]

  On 4/10/2024 at 4:18 PM, MinusAndy said:

Just a thought but could you put the crankshaft elsewhere and run the pistons via rockers? 
 

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Unfortunately what you see int he pic above it's all the space I have. To the right is the worm and sector steering mechanism, which takes up quite a bit of space, and to the left the cockpit - it's a cabrio car so I cannot cheat with the interior space.

[gyenesvi]

  On 4/10/2024 at 10:32 AM, Jurss said:

New parts from kawasaki?

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Those aren't really solving any problem that was not solvable before as they require the same amount of space. They are just not small enough. Plus are unrealistic and have more friction. Thanks TLG.

  On 4/10/2024 at 2:07 PM, Divitis said:

Thanks for the idea! I managed to put this together, that fits the space.

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It does get you a slightly better firing order, but not too much.

  Quote

Unfortunately 2L pistons fall down (you can see one in the photo) and 3l ones would hit the hood.

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Plus this problem. I wish instead of the Kawasaki pistons, TLG produced something more generic and useful, like a 1.5L crankshaft piece (1.5L liftarm with 2 axle holes), or a 2L axle with stop. Both could have helped here and would have been useful for other purposes as well..

On a more constructive note, @Divitis have you seen crankshaft designs that use rotated 1x1 plates with a bar through them? And the pistons could be half pins with tiles on top, held by half plates. Although that only works up to V10 using a 7L half liftarms to hold 5 of them on one side.

Edited April 10, 2024 by gyenesvi

[Murdoch17]

I misread the title as 12V instead of V12 and spent the first half of this thread very confused on where the electric train motor was.  (You can tell I spend a lot of time in Train Tech, can't you?)

[Stereo]

  On 4/10/2024 at 4:46 PM, gyenesvi said:

Those aren't really solving any problem that was not solvable before as they require the same amount of space. They are just not small enough. Plus are unrealistic and have more friction. Thanks TLG.

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I don't think they're as finicky as the 2L liftarms pushing 3L axle with stop that's pretty common design, lots of MOCs I've tried from the 42093 Corvette need tiny adjustments to the axle locations before they'll even roll.  Also you can run them flat or upside down rather than only in a V or inline.  But yeah, in situations where one doesn't work, the other won't either.

[Divitis]

  On 4/10/2024 at 4:46 PM, gyenesvi said:

On a more constructive note, @Divitis have you seen crankshaft designs that use rotated 1x1 plates with a bar through them? And the pistons could be half pins with tiles on top, held by half plates.

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I'm not sure I have. @gyenesvi can you please share an example?

 

  On 4/10/2024 at 4:46 PM, gyenesvi said:

Although that only works up to V10 using a 7L half liftarms to hold 5 of them on one side.

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Yeah, story of my recent life.. 

 

  On 4/10/2024 at 4:46 PM, gyenesvi said:

Plus this problem. I wish instead of the Kawasaki pistons, TLG produced something more generic and useful, like a 1.5L crankshaft piece (1.5L liftarm with 2 axle holes), or a 2L axle with stop. Both could have helped here and would have been useful for other purposes as well..

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I agree that they're too big, following the Lego trend of making ever bigger models.. but they don't seem to have any more friction than the 'classic' engine pieces, at least to my hand.

  On 4/10/2024 at 4:37 PM, Stereo said:

Would it be ok to space the pistons out more?  You could alternate 1x1 bricks and 1x2 bricks with 1 hole so they're 1.5 studs apart, and then use entirely the crankshaft "Type 1" inserted with all the axles in a straight line, so the pistons only rise 1/2 stud, don't drop 1/2 stud.

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I didn't know about this piece variant, very nice to know and clever idea indeed!

Unfortunately, the space is what it is, without a stud to spare.

[Stereo]

https://rebrickable.com/parts/86996/plate-1-x-1-x-23-with-open-stud/ These and round 1x1 plates can stack on a bar (5 plates per 2 studs = 2 square, 1 of the round)

[Divitis]

  On 4/10/2024 at 8:59 PM, Stereo said:

https://rebrickable.com/parts/86996/plate-1-x-1-x-23-with-open-stud/ These and round 1x1 plates can stack on a bar (5 plates per 2 studs = 2 square, 1 of the round)

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Thanks Stereo! I spent a few hours tried similar things but inevitably failed to space the 'bulges' exactly one stud apart to avoid two adjacent pistons being pushed at the same time.

 

An then, a moment ago I simply stacked 6 technic bricks with axle hole... and it works just fine.

Granted, travel range isn't great, but it's sturdy and the motion smooth. Sometimes, easy does it 

PS: Still very open to better ideas of course!

Edited April 10, 2024 by Divitis
hi-res image

[gyenesvi]

  On 4/10/2024 at 5:10 PM, Divitis said:

I'm not sure I have. @gyenesvi can you please share an example?

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The solution I meant has a similar range of motion than the above solution, and is also similar to that of @Stereo

An example is here:

and more details are in this thread:

But yeah, I also thought about those 1x1 bricks with axle holes but thought they would be too edgy and get stuck. Interesting to know that it actually works okay.

[Divitis]

  On 4/10/2024 at 10:21 PM, gyenesvi said:

The solution I meant has a similar range of motion than the above solution, and is also similar to that of @Stereo

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I see, now I get it! Thanks a lot for taking the time to share this :)

Although I think since the 2 plates on the shaft measure 0.8L and the pistons are 1L apart, eventually the assembly goes out of sync and a piston fires twice, maybe?

What I was fiddling with was something like, which would give me equally spaced bulges. But I couldn't connect it to the gear and the frames on both sides.

 

  On 4/10/2024 at 10:21 PM, gyenesvi said:

Interesting to know that it actually works okay.

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They work quite nicely, I can make a video tomorrow if you're curious. The only catch is that the pistons need either an axle with stop or a bush, otherwise they might get trapped in the brick's bottom hole.

Edited April 10, 2024 by Divitis

[Stereo]

You can repeat the pattern of circle-square-circle-square-circle for plates, as that's 2 studs tall, 3 times for a V12, then the last circle is either a tile with bar on top into a half-pin, or use the pin with anti-stud to end the stack.  Which is unfortunately a kinda rare piece to have sitting around in Technic collections.  I only know about it cause of 42178.

Headlight bricks with a bar through their front facing stud would also stack ok, alternating which way they're facing so they touch stud to stud instead of stacking.

[msk6003]

I don't know how this will work on high load situation but this is solution I used on my TC25 car transporter mini.

Edited April 11, 2024 by msk6003

[Divitis]

  On 4/10/2024 at 11:23 PM, Stereo said:

You can repeat the pattern of circle-square-circle-square-circle for plates, as that's 2 studs tall, 3 times for a V12

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What I meant is that the spacing of the plates and that of the pistons is not the same (0.8L vs 1L) so eventually some piston will fire twice (left). But it looks like it can very easily be compensated for (right).

In fact, upon closer look it seems that @msk6003 is doing just that :)

 

[Zerobricks]

You can use toggle joints 32126 to make any size of an engine using half pins.

[Divitis]

  On 4/11/2024 at 8:58 AM, Zerobricks said:

You can use toggle joints 32126 to make any size of an engine using half pins.

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I even tried with lining up minifig neck brackets. 

Unfortunately they aren't thick enough to restrain the pistons' movement. Maybe OK with a 1L pin in a manual model though.

[Stereo]

I suppose you're not actually limited to using a single neck bracket though. And this traps a frictionless pin in both directions, so it's not going to fall out. (this is the thick neck bracket variant, cause it's 1/2 plate thick and fits the grid)

 

Edited April 11, 2024 by Stereo

[Divitis]

  On 4/11/2024 at 7:47 PM, Stereo said:

I suppose you're not actually limited to using a single neck bracket though. And this traps a frictionless pin in both directions, so it's not going to fall out. (this is the thick neck bracket variant, cause it's 1/2 plate thick and fits the grid)

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This is brilliant, thanks for sharing! I'll make sure to keep the possibility in mind for the future. :)

Btw, this is what I had concocted with the bracket part, before realizing the movement is too finnicky with 2L axles. What I really liked about the design is the possibility to cover up most of the pistons with curved slopes, for a more realistic look in a limited space.