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You have GOT to be kidding me

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10K views 35 replies 15 participants last post by  Rubberchicken 
#1 ·


Ian Drysdale (builder of the Drysdale V8 ) sent me these interesting photos. He tells me "the builder's name is Russell.Sutton, a Kiwi living in Australia. The motor (when finished) will displace 8 litres, it has a similar bore and a longer stroke than the XR600. I think the redline is 4,000 rpm or thereabouts, with a planetary gearbox made from a gear set out of a Caterpillar transmission, to bring it down to 2,500 rpm at the prop. Intended use is an "airboat". Its still missing crank and rods, but these are being made."

http://www.eurospares.com/graphics/engine/XR_Radial_03.jpg
http://www.eurospares.com/graphics/engine/XR_Radial_05.jpg
http://www.eurospares.com/graphics/engine/XR_Radial_07.jpg
http://www.eurospares.com/graphics/engine/XR_Radial_08.jpg
(source: here)
 
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#21 ·
Did somebody call?




:happy3:
 
G
#5 ·
that wouldn't work. Its someone playing with your head. Think BMW boxer engine. Are the two cylinders in line? No. Why not? To fit in the two con rods on the crank, so for this you would need 8 and therefore the 8 cylinders all in different positions.

If i am wrong them someone please tell me cause i know i don't know much about engines but this makes sense to me.

If i am right then i'm sorry to burst your bubble guys.:D
 
G
#6 ·
You're wrong :p ;)

You can have a central single big end that rotates to a single offset on the crank, all the radials attach to it. The hardest thing about a radial is ignition timing so that each one pushes at the right time.



Kymmy
 
G
#11 ·
fair enough, i stand corrected. Can see that its that practical a shape though except in aircraft. Looks a bit silly in that motorbike, but i suppose it would work well if its air cooled, unlike a V-twin positioned like in an @.
 
#16 · (Edited)
fair enough, i stand corrected. Can see that its that practical a shape though except in aircraft. Looks a bit silly in that motorbike, but i suppose it would work well if its air cooled, unlike a V-twin positioned like in an @.

i think radial engines have to have an odd number of cylinders if not the conrods hit each other? someone may be able to explain it better than that.
 
#14 ·
Can't think of anything technical to add so I'll just show you my ashtray -



Made from a Spitfire piston!!!


Not just any ashtray - an R.J. MITCHELL SUPERMARINE SPITFIRE ASHTRAY!:D
My mate's Dad used to work in the factory where they made the engines.
 
G
#23 · (Edited)
Rotary (Rotax, W@nkel) engines are totally different from Radials. Quite a few production vehicles have had rotary engines in them and include

Mazda RX7
Mazda RX8
Norton Commander
Suzuki RE5

as well as being now very popular in small aircraft, microlites.



Kymmy
 
#24 ·
Won't it be great when they finally get them to deliver on the promise they show on paper :D
 
#27 ·
Correct me if I'm wrong (and somebody usually thinks I am) but if you have lots of even numbered cylinders don't they work "sympathetically" as in a V6 or V12 i.e. more than one on the same stroke at the same time rather than "progressively" i.e. one after t'other like Kymmy's 5 cylinder pic, for a rotary this would then require an offset crank effectively splitting it into two engines?

The timing for an 8 or more rotary would be hellish if they were progressive :confused: or is that why they seem to be rev limited :confused:

One thing for certain they look fricken wierd on a bike :D
 
G
#28 ·
With odd numbers you always have a single cylinder starting a power stroke at any one time making the power delivery even and smooth. You can though get even numbers but they tend to be layered radials with more than one planes of cylinders. I presume though not sure that the 2nd row would be half a phase out to continue the one cylinder starting a power stroke scenario.

Also radials and rotary engines tend not to be rev limited but more power limited hence they're sometimes known as screamers :)

Kymmy
 
#34 ·
...snip someone is going to post saying they thought "screamers" meant something else :rolleyes::toothy7:
I've often wondered about screamers... now I know :blob:
 
#31 ·
But the boxer's no screamer, that's more like an old bomber, the airhead at least. ;-)

Every so often a Catalina flies overhead here. Dead slow, a pair of droning radials. Lovely sound... (The accompanying spittie is something else, though :mrgreen: )

Had a go in an An-2 once. Big radial engined biplane. That thing is mental. Sick bags were provided... :)
 
#32 ·
But the boxer's no screamer, that's more like an old bomber, the airhead at least. ;-)

Every so often a Catalina flies overhead here. Dead slow, a pair of droning radials. Lovely sound... (The accompanying spittie is something else, though :mrgreen: )

Had a go in an An-2 once. Big radial engined biplane. That thing is mental. Sick bags were provided... :)
would love to have had a flight in one of those





:cool::cool:

had a flight in one of these








not rotary engined but an experience all the same

:cool::cool:
 
G
#33 ·
The boxer engine is no radial as there needs to be a minimum of 3 to be counted as a radial, instead the boxer is counted as a flat twin. The modern radials and especially rotaries are more screamers than the older ones, amazing for engines that were basically designed 80+ years ago and still use push-rods (Jenna and I were trying to think of designs that would use a camchain and could only come up with a long chain around the whole circumfrance which would be a pain to time up)

Also going away from radials and onto rotaries can anyone answer a simple question?

You see from my animated gif that the concentric movement of the piston allows compression against the piston face, but what keeps the compression in check on the top and bottom faces???? 13uggered if Jen or myself can figure it out....best Jen could come up with is just a flat finished face on piston and crankcase but tollerances and finishes would have to be amazing for that to work???
 
#35 · (Edited)
Quote "but what keeps the compression in check on the top and bottom faces???? 13uggered if Jen or myself can figure it out....best Jen could come up with is just a flat finished face on piston and crankcase but tollerances and finishes would have to be amazing for that to work??? "




There is no compression as such in the other chambers because there are no valves only ports. As the rotor moves around the chamber, each of the three volumes of gas alternately expands and contracts. It is this expansion and contraction that draws air and fuel into the engine, compresses it and makes useful power as the gases expand, and then expels the exhaust. The combustion chamber is machined into the rotor face.

 
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