Discussion in 'Firewall Forward / Props / Fuel system' started by Hephaestus, May 12, 2019.
Looked up AV-36, is this it?
Cool! So you are going mower with that? It should be fun!
That is part of the reason for my interest in the 810. I intend to develop a system to turn it into an AV-45. Should increase my market base. A couple used Rotax, but they are getting harder to find. The 810 will be at the bottom end of the Hp range of the AV-45 but should be usable.
Head for the updrafts.
I don't know if it helps anyone but GrabCAD has 3D models. They also have a belt reduction model for them.
Well, this does explain your interest in putting the crankshaft up and the cylinder heads down! For most planes with typical landing gear, the approx 4" difference in crank height can be more easily accomodated than with the squat, semi-submerged wheels of an AV-45.
It does look like the cylinder liner skirts do extend perhaps enough for inverted engine.
Actually, I started down the inverted path for my Quickie. I'm still undecided about using the inverted for the wing. I've got to get enough of it into CAD to see how things fit.
There is just something visually wrong with a Quickie and 'power bulges' like the MC-30 and SD-1.
The side walls will drain directly into the cylinders for about 45 degrees. The rest should drain down the valley into the original breather and into the valve covers. Next time I have it apart I'll probably tear it down to a bare block. If I'll measure the thickness of the cylinder walls. It would be nice to stuff a 3.5 inch sleeve in and leave a bit sticking up around the full diameter. 912cc would be nice too. The added cost - not so much.
Just so no one else has to go looking for a service manual for the 810cc. Here are 2 versions that should work?:
I use ethanol free mogas in all my small engines. My emergency scooter, too. It often goes a while without being ridden and doesn't have a sealed tank like modern cars.
100LL will leave deposits. Nowhere near as bad as the old high octane stiff, though. I've heard other people advocate 100LL, but if the valve seats are ok for lead free, ethanol free mogas is the way to go IMHO.
Hotwings, could you measure trhe oil pump capacity? Grease it to a flat plate and measure the volume between rotors.
With aftermarket cams, the centrifugal compression release would involve a fair bit of machining, but a solenoid operated one would be a lot easier. Many of them delayed inlet valve closing.
You bought the rights to the AV36?
Such a messy way to measure the volume.......but probably quicker than putting it into CAD. Best guess is around 8 ml. Will be interesting to see how close I am when I get to it - maybe tomorrow.
<< >> Seemed like a quicker way to get to where I was heading rather than finding the time to fully develop my doodles into a flying wing. At least I have a proven base to work from now. But the plans are in pretty poor shape after being unrolled for copy so many times. They were never put into digital format and some are still in French....and mirror image too.
I downloaded those two manuals. The specs page are for smaller engines, not the 810.
Yes---Yes, you did. Thanks fer nuthin!
The diagram and discussion of the lubrication system contained in the B&S 810cc manual doesn't tell us much about how the rockers get lubricated --or the wrist pins.
(Looking at the pictures by Hot Wings back here: https://www.homebuiltairplanes.com/...anguard-conversions.31620/page-22#post-476536 )
1) If somebody wants to use low carbs under the engine, putting the crankshaft high and the heads low does simplify the induction runner routing and reduces the problem of droplet formation that is a particular issue in longer runners (whether driving the prop from the flywheel end or the PTO shaft).
2) Unless there are parts missing, it seems like that OEM baffling/tin wouldn't do a very good job of passing air through those fins on the (hot!) back side of the engine, near the exhaust valves.
Thanks very much for the manuals, weights, and pictures. Is this a Commercial Series engine?
That is why I asked about the manuals earlier. Apparently B+S hasn't yet found it necessary to publish one that specifically includes the 810. Other than the bore diameter all the rest seems to be the same and interchangeable.
It is a model 49M877 - IIRC. Has Husqvarna logo. This is the closest I can find right now. Mine does not have the electronic fuel management.
B&S has a web portal (here: https://www.thepowerportal.com/Login.htm ) that sounded like it might be useful to us. Do you have any experience with it? The materials reportedly include documents and videos made for use in VoTech education classes featuring B&S products. I attended school a few years ago, I'm wondering if I can get student access.
Yeah, the crank journal specs are same as my 500cc single cylinder, it appears.
My Horizontal GX 670 shop manual has detailed description of oil pressure to valves and rockers.
I don't see that on the vertical Briggs.
Probably partly why Honda cost $300 more.
Of maybe vertical don't need oil pressure to valves and horizontal do?
My guess was way off. 4.75 ml avg of 2 measurements.
Inner lobes = 19.31 mm thick.
Outer = 19.29 mm thick.
Fit in pump recess is essentially zero clearance to cover plate.
I'm not sure about how the lube gets to the rockers/valve stems on the vertical shaft B&S engines, but it apparently does. I don't see any obvious galleys where the head meets the cylinder/block, there are just holes for the bolts and the two large cavities for the pushrods. If the oil isn't going through the pushrods under pressure then it can only be splashing in through the large openings for the pushrods (which seems improbable, though that would be the obvious >return< route for the oil to get back to the sump.
There are some clues in an SD-1 (SE33 engine) build video/slideshow. This is not a subject I know well, so I'd welcome comments from those more familiar with what is going on/what is typically done.
Below: This is the left head. The taped-over fitting is what I believe may be the oil return from that head (though I'm not sure why the oil couldn't just drain down through the pushrod galley and into the sump, then to the scavenge pump that will need to go there). If so, what is in the grey box between the valve cover and the black hose/nipple? Below the valve cover is a blue fitting fed by an AL line, I'd guess this is likely the oil feed to that set of rockers/valves. Maybe a spray bar inside to send the oil to the best spots?
Below: This is another picture of the left head (note the sticker: The B&S model is 49S877-0004-G1). More baffling is fitted, but we can see the grey (oil supply line?) is fed by a T-fitting with the other branch going toward the other head.
Below: Left head again, but now a blue hose has been connected to it (leads to? Remote air/oil separator and remote oil sump/tank?). Behind the blue hose is a control cable for the choke (right?).
Below: Here we see the other head (right side). The grey AL (oil feed?) line goes to blue AN fittings leading into the head, and a fitting and black hose lead from the valve cover to drive the fuel pump on top of the induction runners. I don't see an obvious oil return line on this side (oil returns to the bottom of he crankcase through the pushrod galleys?) . BTW, that carb looks a lot like a stock B&S model, though as BBerson suggested elsewhere, it could be one from a larger engine to accommodate the higher (claimed) 33 HP. I'm not sure how we could adjust mixture on any of those carbs, and I haven't noticed a mixture control in pictures of SD-1 cockpits (but they could certainly be there). I believe the control cable that is visible clamped to the right side of the carb bracket is the throttle. I suppose the black item (pink spade connector on top) that appears might connected to the fuel line to the fuel pump might be a fuel solenoid/anti-backfire solenoid. If so, I'd look into accomplishing that function some other way in this aviation application.
So,in addition to my newby questions above (and corrections of anything I've guessed wrong about), I'd want to know where the feed for this pressurized line comes from, if the stock oil pump is up to the task, etc. IIRC, Hot Wings mentioned he liked this 810cc engine because the opportunity to retrofit another oil pump was easy I'd like to learn more about that. Also, this feeding of oil to the rockers/valves offers a good opportunity to go beyond lubrication and flow a >lot< of oil through that area to remove heat from the exhaust valve stems and the back of the head. This might require use of a low pressure/high volume pump of some kind.
Apologies for the long post.
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