[Fot] Duke Engines

[Duncan Charlton]

Hi Michael,

We're not too far from being able to see whether its complexity makes it 
impractical to operate or produce. Since Mike is building a physical 
model, he's encountering many of the production obstacles, so he can 
finesse the finer details as he goes along.  Perhaps many parts = 
unacceptably higher cost; however I think there are only two types of 
bell cranks used.  It may be an imperfect comparison, but a Wankel 
rotary has a low parts count and very few moving parts but as far as I 
know isn't any cheaper to produce.  The different packaging requirements 
obviously create a drawback.

Mike did not start from the question, "how do I remove the side loads on 
the pistons?"  I think if you asked him about that, he would say that it 
was a side benefit of the arrangement.  Note that, except for two, the 
bearing surfaces all are essentially wrist-pin bearings which rock back 
and forth rather than rotate -- and this is where the expected big gains 
are. Wrist pin bushings get by with a little splash of lubrication and 
don't fail very often.  They produce much less heat than the 
oil-shearing action of the rod big ends and mains.  Lowered power loss 
through the bearings is where his claims of greater efficiency come 
from.  Lowered lubrication requirements (fewer bearings requiring a 
pressurized oil supply) suggests lower power loss due to oil pumping.  
Lowered heat production by the wrist pins means cooling requirements are 
lower, so a smaller cooling system should be required; in fact, I wonder 
if only the heads will require water-cooling for best efficiency.  Less 
mass in the car means lighter brakes and tires, etc.

I'm curious about your suggestion about a destructive rocking couple.  
I'm not educated enough about these things to recognize it in this 
design.  Note that the opposing pistons move in opposing directions, 
unlike the usual flat-4 boxer engine.  Wouldn't this completely cancel 
out the rocking couple?

Keep in mind that the animation on the home page is just to get across 
the concept and doesn't necessarily represent the relative dimensions, 
and therefore mass, of the internal parts.  Valve actuation is by 
pushrod, by the way -- when I last spoke to him I think he was using two 
camshafts to better fit the layout.

Duncan


On 3/22/14, 4:15 PM, Michael Porter wrote:
> On 3/22/2014 1:49 PM, Duncan Charlton wrote:
>> Here is one that*is* new under the sun, different enough to have
>> generated quite a few patents.  You can see it at: 
>> www.brickleyengine.com
>>
>>
>
> I can see why he's getting resistance.  It's clever, but impractical.  
> In the bottom end, he has twenty moving parts, whereas the normal 
> four-cylinder has nine.  And, when he's doing his bearing drag 
> calculations, he's conveniently ignoring that he has more than thirty 
> bearing surfaces, where the traditional four-cylinder bottom end has 
> thirteen.
>
> If he's going to operate standard valves, he has to have some sort of 
> camshaft to operate them, just like a traditional engine (not shown, 
> likely because the arrangement would have to be rather complicated, 
> given that the camshaft can't be placed at the centerline of the 
> engine as in a flat four).  That problem might be solved by having a 
> minimum of four overhead camshafts, one at each cylinder, run by a 
> central chain off the crank, but that again raises the number of 
> bearing surfaces and the number of moving parts, and it would be one 
> helluva long chain and would require a complicated system of 
> tensioners and guides.
>
> He includes accessories in the friction calculations, but he'd still 
> have to have them with his engine, so why are they factored in for the 
> traditional engine, but not his? After all, one of the bigger 
> losses--the oil pump--would have to be factored in for both.
>
> The envelope doesn't seem to be very compact and would be ill-suited 
> for automobiles, because it's evidently quite tall and wide (and gets 
> bigger still when cylinder heads and valve gear are added). 
> Structurally, it looks quite heavy, so I doubt that the rpm limit 
> would be high enough for modern automobile use (that range might be 
> extended a bit by using forged aluminum bits, at much increased 
> cost).  I'm not sure I'd want to run it very fast, anyway, because the 
> vibration from the multiple rocking couples set up by the piston 
> arrangement and the reciprocating parts could hammer the rod bearings 
> in short order.
>
> It's a lot of complexity to get around one thing--friction caused by 
> side loads on the piston due to connecting rod angular motion. That's 
> the only real frictional gain this design achieves, at considerable 
> expense, and that gain is probably erased by the losses incurred from 
> the additional moving parts.
>
>
> Cheers.