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Re: Honda Power Unit
Posted: 17 Feb 2017, 03:05
by 63l8qrrfy6
glenntws wrote:wuzak wrote:glenntws wrote:Like I said before, I think there is no way that they use forked rods. However, since this rumor goes around again and again, I think I found a solution which (I think atleast) is comparable to the one from Honda.
Was about two hours of work in Inventor. Nothing perfect, just made up fast and simple models. Two little simulations give a safety factor of 1.4 at 350bar peak cylinder pressure. I'm sure that, if this model would get perfectionated, they could really have two banks without cylinder offset without using these forked rods no one wants
The view from top:
http://fs5.directupload.net/images/170216/3ccxz42y.jpg
The crankshaft with U-shaped crankpins:
http://fs5.directupload.net/images/170216/54sejwhb.jpg
Also, I'm right now working on a little model of the cylinder head which implements the idea I gave yesterday with the combustion priciple. Maybe I can also realize some little CFD-Simulations, which could give a further hint how things look like in reality.
Can I ask, why U-shaped crank pins?
In your analysis, did you include piston and rod accelerations, which must be significant at 10,000rpm+?
My first thought is that arrangement would induce a side load on the piston to compensate for the moment caused by having the support (the bearing) offset from the load (combustion forces and piston loads).
The U-shaped crank Pins increase the bearing area which in turn makes the cranktrain safer for higher loads. Also, the oil naturally gets pushed more outwards in higher rpms which Supports the lubrication in the complete bearing area.
Accelerations are not included, but I think they are not a big Problem. What I do think, is that the side load on the piston is fairly high at these rpms, so i think that a lower side support would be necessary (like you find it in many street vehicles).
Then again, it's pretty sure that Honda (like all other manufacutrers) uses steel as a material for the piston. From my experience, I would go for steel at everything higher than 20MPa Peak cylinder pressure. Using steel also dramatically increases the possible side load. I will make some screenshots of the simulations later.
Actually a steel piston allows the pin bore to sit higher in the piston allowing for either a longer rod (therefore lower side loads) or a shorter deck. The other advantage is that the skirt overall size can be reduced, further decreasing friction. The contact patch is arguably easier to optimize.
That being said, i doubt all manufacturers use steel pistons.
Re: Honda Power Unit
Posted: 17 Feb 2017, 03:43
by PlatinumZealot
godlameroso wrote:If you're brave you can also remove the center main bearing journal and try to figure out another way to control thrust forces and crank harmonics, but that's the least likely solution.
Reduce the thickness of the counter weight near the centre of the crank.
Curve the connecting rods into a semi-bow shape so to the banks are not staggered. The will have enough clearance so the rods dont interfere with each other on the down stroke.
Left bank rods are forged with a bend like this in side view the square is the piston and bracket is the rod:
[]
(
Right bank are bent like this in side view:
[]
)
Simple way to get the opposing bores centred with any finicky forks nor weakening the crank.
Re: Honda Power Unit
Posted: 17 Feb 2017, 03:46
by PlatinumZealot
glenntws wrote:Like I said before, I think there is no way that they use forked rods. However, since this rumor goes around again and again, I think I found a solution which (I think atleast) is comparable to the one from Honda.
Was about two hours of work in Inventor. Nothing perfect, just made up fast and simple models. Two little simulations give a safety factor of 1.4 at 350bar peak cylinder pressure. I'm sure that, if this model would get perfectionated, they could really have two banks without cylinder offset without using these forked rods no one wants
The view from top:
http://fs5.directupload.net/images/170216/3ccxz42y.jpg
The crankshaft with U-shaped crankpins:
http://fs5.directupload.net/images/170216/54sejwhb.jpg
Also, I'm right now working on a little model of the cylinder head which implements the idea I gave yesterday with the combustion priciple. Maybe I can also realize some little CFD-Simulations, which could give a further hint how things look like in reality.
Great minds think alike!
However thrust loads would be the biggest issue. And thrust bearings or maybe a conical journal would be needed.
Re: Honda Power Unit
Posted: 17 Feb 2017, 03:54
by PlatinumZealot
glenntws wrote:wuzak wrote:glenntws wrote:Like I said before, I think there is no way that they use forked rods. However, since this rumor goes around again and again, I think I found a solution which (I think atleast) is comparable to the one from Honda.
Was about two hours of work in Inventor. Nothing perfect, just made up fast and simple models. Two little simulations give a safety factor of 1.4 at 350bar peak cylinder pressure. I'm sure that, if this model would get perfectionated, they could really have two banks without cylinder offset without using these forked rods no one wants
The view from top:
http://fs5.directupload.net/images/170216/3ccxz42y.jpg
The crankshaft with U-shaped crankpins:
http://fs5.directupload.net/images/170216/54sejwhb.jpg
Also, I'm right now working on a little model of the cylinder head which implements the idea I gave yesterday with the combustion priciple. Maybe I can also realize some little CFD-Simulations, which could give a further hint how things look like in reality.
Can I ask, why U-shaped crank pins?
In your analysis, did you include piston and rod accelerations, which must be significant at 10,000rpm+?
My first thought is that arrangement would induce a side load on the piston to compensate for the moment caused by having the support (the bearing) offset from the load (combustion forces and piston loads).
The U-shaped crank Pins increase the bearing area which in turn makes the cranktrain safer for higher loads. Also, the oil naturally gets pushed more outwards in higher rpms which Supports the lubrication in the complete bearing area.
Accelerations are not included, but I think they are not a big Problem. What I do think, is that the side load on the piston is fairly high at these rpms, so i think that a lower side support would be necessary (like you find it in many street vehicles).
Then again, it's pretty sure that Honda (like all other manufacutrers) uses steel as a material for the piston. From my experience, I would go for steel at everything higher than 20MPa Peak cylinder pressure. Using steel also dramatically increases the possible side load. I will make some screenshots of the simulations later.
Steel piston problem as far as the public knows is not solved yet for small petrol engines. Oil gets coked up in the rings. See the steel piston thread.
Re: Honda Power Unit
Posted: 17 Feb 2017, 05:59
by gruntguru
PlatinumZealot wrote:A problem of TJI spark plug nozzles when used with petrol is soot blocking them up.
Interesting. Your source?
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:01
by gruntguru
godlameroso wrote:Out of left field thought, I don't see anything in the regulation stating maximum amount of main bearing journals, I guess that would be your way of shortening the engine.
Surely the length of the engine is dictated by the bore diameter?
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:07
by gruntguru
roon wrote:•Does the turbine benefit more from six evenly (as possible) spaced exhaust pulses, or fewer, larger pulses? Previous seasons showed us tuned length headers, so presumably thae answer at least used to be "six." Perhaps MGUH could 'torque fill' between bigger pulse-gaps.
Maximum number of evenly spaced exhaust pulses sharing an exhaust manifold without loss of blowdown energy is three. That is why the turbines have two entry ports with three cylinders feeding each. Using a 120 deg crank, each bank becomes an even-firing 3 cylinder which simplifies the plumbing - one bank feeds each turbine entry.
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:24
by gruntguru
Not sure what are the objections to fork and blade rods. In hydrodynamic terms you effectively have three bearing shells sharing the journal instead of two, ie four leakage paths instead of three. Since the two inner faces are low relative velocity (forked rod rocking relative to blade rod) and the axial tolerance between fork and blade much easier to control, the clearances could be closed up and perhaps even sealed completely with an o ring, piston ring or labyrinth seal. The result would be better hydrodynamic performance than side-by-side rods. From there you can reduce the length and or diameter of the crankpin, with a reduction in friction.
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:32
by wuzak
gruntguru wrote:godlameroso wrote:Out of left field thought, I don't see anything in the regulation stating maximum amount of main bearing journals, I guess that would be your way of shortening the engine.
Surely the length of the engine is dictated by the bore diameter?
And the bore spacing.
The only real saving to be had is to have the left and right banks aligned, as we have been discussing and as was common in the big aero engines.
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:38
by godlameroso
gruntguru wrote:godlameroso wrote:Out of left field thought, I don't see anything in the regulation stating maximum amount of main bearing journals, I guess that would be your way of shortening the engine.
Surely the length of the engine is dictated by the bore diameter?
The bores are 80mm, so yes you are correct, also important is bore spacing, deck dimensions water jackets, and oil passages. Theoretically what would be best case scenario for block length ~400mm?
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:38
by gruntguru
wuzak wrote:gruntguru wrote:godlameroso wrote:Out of left field thought, I don't see anything in the regulation stating maximum amount of main bearing journals, I guess that would be your way of shortening the engine.
Surely the length of the engine is dictated by the bore diameter?
And the bore spacing.
The only real saving to be had is to have the left and right banks aligned, as we have been discussing and as was common in the big aero engines.
Thanks Wuzak. Posted that before I read the rest of the thread.
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:39
by ncassi22
Still on valving the prechamber
.... It should provide better control over timing of ignition/directing jets etc. This would work great; even better if you could control it with a solenoid. Just add a plug and drill some holes for the jets !
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:40
by gruntguru
godlameroso wrote:gruntguru wrote:godlameroso wrote:Out of left field thought, I don't see anything in the regulation stating maximum amount of main bearing journals, I guess that would be your way of shortening the engine.
Surely the length of the engine is dictated by the bore diameter?
The bores are 80mm, so yes you are correct, also important is bore spacing, deck dimensions water jackets, and oil passages. Theoretically what would be best case scenario for block length ~400mm?
How about 260mm? 5mm wall thickness.
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:41
by wuzak
gruntguru wrote:wuzak wrote:gruntguru wrote:Surely the length of the engine is dictated by the bore diameter?
And the bore spacing.
The only real saving to be had is to have the left and right banks aligned, as we have been discussing and as was common in the big aero engines.
Thanks Wuzak. Posted that before I read the rest of the thread.
It's hard work keeping up with this thread. Go away for a half a day and at least 3-4 pages are added!
Re: Honda Power Unit
Posted: 17 Feb 2017, 06:42
by godlameroso
ncassi22 wrote:Still on valving the prechamber
.... It should provide better control over timing of ignition/directing jets etc. This would work great; even better if you could control it with a solenoid. Just add a plug and drill some holes for the jets !
http://www.leeimh.com/images/dwg-inserts-reverse.gif
Could a solenoid react fast enough, maybe piezoelectric valve?