18 replies to this topic

[DeadSquare]

If Mr Brown hadn't stolen 72% of my pension, I had often wistfully thought that in retirement I would get a crank and matching cam made.

 

Not just the usual crank though. My crank would, in effect, be sliced through the center main and the one halve rotated through 180 degrees.

 

This would mean that instead of getting two sucks through one side of the inlet manifold, which interfere with each other, and then two suck through the other, the sucks would be evened out and not interfere with any two cylinder's filling.

 

There could be a corresponding disadvantage because when cylinder 2 exhausts, gas could back-flow into cylinder 3, but this can be overcome by enlarging the exhaust port and inserting a divider in the center.

 

Discuss:- !

 

 

 

 

[Swift_General]

I'm not sure this solves the problem. If I understand what you're saying - by rotating the crank 180 degrees between cylinders 2 and 3 each crank pin would then be 180 degress apart with repect to each other, so 1 and 3 at TDC with 2 and 4 at BDC. This would of course upset the firing order. So with your crank valid firing orders could be 1-2-3-4 or 4-3-2-1. Either way you will have 2 cylinders sharing the siamesed inlet port with sucessive intake strokes. So if 1-2-3-4 you'd have cylinder 1 on its intake stroke immediately followed by 2, so there would still be port robbing. Also the power pulse will either make its way up the crank towards the flywheel or away from it rather than the pulses being distributed more evenly. I'm guessing 1-2-3-4 will set up an oscillation - so as the plugs fire moving along the crank the engine rocks one way, then pings back as the process starts again.

[nicklouse]

boring. just super charge it and blow through the exhausts and out through the inlets. cam ground to suit. has has been done before though.

[Retroman]

This is a real brain twister

 

I have wondered about similar for years as it makes sense

 

After an A4 of working out...

 

The standard firing order is 1 3 4 2 so by swapping the crank phasing at one end 180 degrees it changes things

 

So cylinders 1 / 2 don't change... 3 and 4 effectively swap round

 

So the crank instead of having 1 / 4 at BDC and 2 / 3 at TDC as standard....1 and 3 are at BDC and 2 / 4 are at TDC

 

So the firing order would be  1 4 3 2   according to my scribbling

 

So all the standard A series charge robbing etc would still happen

 

The firing order can't be 1 3 4 2   as with the crank re-phased 1  and  3  are on the same stroke [ up or down ] at the same time

 

So if 1 is firing 3 must be filling etc

 

So in theory the 1 3 4 2  firing order might be as good as it gets on an A series but just re-phasing 1/2 the crank would not do it

 

I wonder would it work with cylinders 1 / 2 phased opposite to 3 / 4

 

More scibblings needed

[Swift_General]

The only way to solve this on a 4 cylinder engine is to have 1 and 2 at TDC with 3 and 4 at BDC. So a valid firing order would be 1-3-2-4 (i.e. as per title of thread). But this means rotating the crank 180 degrees between 1 and 2, between 2 and 3, and 3 and 4 to get cranks pins 1 and 2 inline, and 3 and 4 inline and 180 degrees relative to 1 and 2. This would certainly deal with the charge robbing issue, but I suspect there would be a issue with the balance of the crank.

[DeadSquare]

This is a real brain twister

 

I have wondered about similar for years as it makes sense

 

After an A4 of working out...

 

The standard firing order is 1 3 4 2 so by swapping the crank phasing at one end 180 degrees it changes things

 

So cylinders 1 / 2 don't change... 3 and 4 effectively swap round

 

So the crank instead of having 1 / 4 at BDC and 2 / 3 at TDC as standard....1 and 3 are at BDC and 2 / 4 are at TDC

 

So the firing order would be  1 4 3 2   according to my scribbling

 

So all the standard A series charge robbing etc would still happen

 

The firing order can't be 1 3 4 2   as with the crank re-phased 1  and  3  are on the same stroke [ up or down ] at the same time

 

So if 1 is firing 3 must be filling etc

 

So in theory the 1 3 4 2  firing order might be as good as it gets on an A series but just re-phasing 1/2 the crank would not do it

 

I wonder would it work with cylinders 1 / 2 phased opposite to 3 / 4

 

More scibblings needed

Edited by DeadSquare, 04 December 2018 - 11:21 PM.

[Swift_General]

This is a real brain twister

I have wondered about similar for years as it makes sense

After an A4 of working out...

The standard firing order is 1 3 4 2 so by swapping the crank phasing at one end 180 degrees it changes things

So cylinders 1 / 2 don't change... 3 and 4 effectively swap round

So the crank instead of having 1 / 4 at BDC and 2 / 3 at TDC as standard....1 and 3 are at BDC and 2 / 4 are at TDC

So the firing order would be 1 4 3 2 according to my scribbling

So all the standard A series charge robbing etc would still happen

The firing order can't be 1 3 4 2 as with the crank re-phased 1 and 3 are on the same stroke [ up or down ] at the same time

So if 1 is firing 3 must be filling etc

So in theory the 1 3 4 2 firing order might be as good as it gets on an A series but just re-phasing 1/2 the crank would not do it

I wonder would it work with cylinders 1 / 2 phased opposite to 3 / 4

More scibblings needed

You are correct. It should be 1432.

But this doesn't solve the charge robbing problem. As you'll have cylinder 1 intake immediately after 2, then cylinder 3 intake immediately after 4.

[DeadSquare]

Well it looks as though, as it doesn't seem to work, that it is just as well that I haven't got the money, to waste !

[Retroman]

The  1 3 2 4 firing order would work with the crank phased  1 / 2 at TDC  and  3 / 4 at BDC

 

But would it work balance wise ?  with both ends of the crank dead opposite ?

 

I think it would be more of a flex and strength problem

 

as rather than having 2 big ends opposite each other at each side of the centre main, it would have 2 big ends at each side....

 

Probably stressing and flexing the centre main too much

 

That said a pension pot would probably not be big enough to investigate

[Spider]

I recall scribbling something down a while back on these kinds of configurations.

 

The Harmonics from just about any other order than the 'standard' 1,3,4,2 would become a headache.

 

I ** think ** too, you may need Balance Shafts.

[Steve220]

You would. It'd shake like a poopin dog otherwise.

Edited by yeti21586, 05 December 2018 - 05:45 PM.
Don't try and avoid the swear filter

[CMXCVIII]

It does look as though Gordon Brown stealing your pension saved you from shaking your teeth out!

 

And presumably investing in ever bigger and stronger centre bearing main straps!

 

Jon

 

 

- ETA - I'd missed Retroman's 'further scribble' that already made that point

Edited by CMXCVIII, 05 December 2018 - 09:18 AM.

[mini13]

the 1&2 up 3&4 down crank has been done before, I remember vizard mentioning it somwhere, but didnt say how good or crap it was, IIRC it was an inline motor built for a sprite in Aus.

[DeadSquare]

Pursuant to yesterday evening's excellent posts, at quarter to five this morning, I went and found my Meccano.

 

I have made a 3 main bearing shaft, in such a way that I can change the angle of the cranks.

 

After a couple of hours of fiddling, I have come to the conclusion that there is only one design that produces the desired firing order.  For simplicity of explanation only, cylinders 1&2 share a crank pin, (there would be plenty of room for a counterbalance blade between the big-ends), and 3&4 share another.

 

The firing order can then be either 1324 or 1423.

[Retroman]

Back to childhood excellent....So we are all singing from the same sheet

 

Would be interesting to ask DV, if it was Aus Spider might know...?

 

Does DV still do forums now ? he used to be on piston heads