I'd rather collect with a baseball bat, or maybe a hammer.
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T head engine by Brian
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Originally posted by Toolguy View PostLooks really nice, Brian. Can't wait to see it run! That one ought to have some torque with 2 flywheels.Last edited by aostling; 09-03-2021, 07:41 PM.Allan Ostling
Phoenix, Arizona
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Originally posted by aostling View Post
I agree it ought to have impressive torque, but not because of the flywheel inertia. Average (mean) torque is equal to the product of BMEP (brake mean effective pressure) and displacement. BMEP will vary with load and speed.25 miles north of Buffalo NY, USA
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Originally posted by nickel-city-fab View Post
I'm learning something here -- I thought it varied with the stroke length??
What makes for a higher BMEP? More energy released by the combustion. This is affected by air-to-fuel ratio, compression ratio, and (I suppose) ring sealing. I don't pretend to know then all.Allan Ostling
Phoenix, Arizona
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The missing element is rpm.
The point in the rpm range where it occurs can be different. If you have a long stroke engine, it will generally have it's torque lower in the rpm range than a short stroke engine.
I had an S10 and a Volvo 240. Similar "power" in each. But the Volvo was significantly longer stroke than the S10. The 240 would "lug out", but the S10 would not. The 240 simply had it's torque at a lower rpm than the S10. For max power, the S10 had to really "scream" at a high rpm. (and at that RPM, the actual torque could be considerably lower for the same power).
Note that at similar power, the torque numbers will be different... the peak and average torque for the same power MUST be larger for a lower rpm engine, if the power is similar.
You need to look at what is being held the same in the example. Is it TORQUE that is being held the same? Or is it POWER? You will get different results depending.... It can get confusing.4357 2773 5150 9120 9135 8645 1007 1190 2133 9120 5942
Keep eye on ball.
Hashim Khan
Everything not impossible is compulsory
"There's no pleasing these serpents"......Lewis Carroll
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Torque is what does the work, power is how fast that work gets done.
You want more of either in a given displacement size engine, the answer is simple even if the execution is not, burn more fuel.
Brian has been burning the midnight oil and look how much he gets done!Home, down in the valley behind the Red Angus
Bad Decisions Make Good Stories
Location: British Columbia
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This is the part where I never know what is going to happen next. The second flywheel has been keyseated, grub-screwed and installed. I have had some engines start right up at this point, amazing and delighting me. I have had engines that ran, but needed considerable tweaking before they ran well. And I have had engines that wouldn't run at all, because something was out of adjustment, the valves leaked, because I had machined something wrong, or perhaps the small engine Gods were just messing with me.---Wish me luck!!!---BrianBrian Rupnow
Design engineer
Barrie, Ontario, Canada
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Okay---this one isn't going to take right off and surprise me. Fuel is getting ignited, cylinder is getting warm from firing. I'm not feeling a lot of compression here. The old "oil down the sparkplug hole" trick isn't bringing the compression up any, so this infers that the rings are doing their sealing alright. I will check again to make sure that there is daylight between the valve stem and the lifter when the lifter isn't up on the cam. (this will hold the valve open and no compression will be developed.) Since it does seem to be firing more or less consistently when driven by my electric drill, I will now put an electric motor to driving it, and see if the valves will seal up from the pressure created by the engines firing. if it wasn't firing at all, I wouldn't do this.Brian Rupnow
Design engineer
Barrie, Ontario, Canada
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It seems that I have a leaking exhaust valve. Rather than screw around with everything bolted to the engine, I have made a "dummy cylinder" to bolt the cylinder head to. It is an exact copy of the cylinder, but without the center hole for the piston. First thing to check is whether the valve can be rotated into a position that doesn't leak. That technically shouldn't happen, but it sometimes does. Without changing anything on this set up, I can seal the leaking exhaust with my thumb and thus check the intake valve for leaking. I know that I used this same piece of equipment with the "blow yer guts out" test to see if the valves were leaking or not. They didn't seem to be then, but everything gets handled a great deal between that test and when the engine is finished. Today I will test things at 40 psi.
Brian Rupnow
Design engineer
Barrie, Ontario, Canada
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Compression has improved. Engine is now firing regularly along with power drill as I attempt to get it to take off and run on it's own. Cylinder is getting hot from firing. I am now going to take my degree wheel and check the ignition timing. The common knowledge out there is that four cycle engines should fire about 20 degrees before top dead center. Lots of puffs and snorts from the engine but haven't found the sweet spot yet.Brian Rupnow
Design engineer
Barrie, Ontario, Canada
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Originally posted by brian Rupnow View PostCompression has improved. Engine is now firing regularly along with power drill as I attempt to get it to take off and run on it's own. Cylinder is getting hot from firing. I am now going to take my degree wheel and check the ignition timing. The common knowledge out there is that four cycle engines should fire about 20 degrees before top dead center. Lots of puffs and snorts from the engine but haven't found the sweet spot yet.
What does the compression feel like spinning the engine over by hand with the flywheel?Last edited by Sparky_NY; 09-04-2021, 02:26 PM.
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