Briggs & Stratton Vanguard 23hp build

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TiPi

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The low idle speed is not that critical on a draggy plane. But on a Luciole or SD-1, you have trouble landing if the engine idles at 1,100 or above. The other problem adding to this dilemma is the fixed timing, resulting in a very harsh low idle. The Luciole conversion is replacing the standard coils with an electronic ignition and I assume, variable timing built in.
 

bl_dg

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Thrust bearing:
1l Is it needed? Finding info on the SD-1s and Lucioles now using them could probably tell a lot. By all accounts, Colomban et al spent a lot of time working through all aspects of their B&S 627 conversion.
2) If there's a need, room, and enough oil splash, a shim or two with oil grooves might be all the "bearing" that's needed.
There are strong indications that the vertical engine case half won't work with the stock horiz case half, crank, and cam. It would be an amazing coincidence if by chance shims on one or both ends in combination with other parts solved two problems (thrust bearing and rotating part alignment).
My suspicion is that the use of the vertical shaft case half will likely be a dead end, but maybe not.
Well, the engine probably wasn't designed for -any- significant thrust loads, so I would fell better knowing there was a thrust washer or roller bearing in there. Who knows, by the time I'm done, I'll be an 'et al'.
 

bl_dg

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I have built multiples of both vertical, and horizontal Vanguard engines. Most were the 18HP. IIRC, the gasket for both was the same, so the cases MIGHT be interchangeable. From my experience (mowers and industrial applications), the horizontal shafts had a ball bearing on the PTO end and aluminum on the flywheel, while the verticals had aluminum on each end. The verticals did have a longer bearing surface.
One thing I can tell you: the Vanguard engines DO NOT LIKE TO IDLE SLOW. I rebuilt / salvaged ta least three (all horizontal applications) that suddenly had connecting rod failures due to oil starvation - yet were full of oil. I only recently found out about the minimum idle of 1100 RPMs (there is a special governor spring to maintain this minimum speed - many idle at around 1700) The lower idle speed aparently doesn't provide adequate oil pressure for the connecting rods.
While there may not be enough "meat" on the flywheel end, I would think machining a little off the PTO end bushing (vertical application) and installing a roller thrust bearing with two washers. The ball bearing is not a press fit on the crankshaft. Dennis
Thanks for the heads-up on the idle speed! (Another nugget of info.) Yes - when I was taking the back cover apart, I was surprised at how small the internal oil passage was, compared to the size of the filter and the oil cooler. I'll add that to the list of things to get base line data on. (rpm vs oil pressure)

For the tractor installation, I won't know what I have to work with until I pull the engine apart.

If I did a pusher installation, I agree, there is enough material on back cover to machine clearance for a thrust bearing.
 

bl_dg

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Got the first club planed down square. Can't do much to avoid the 'snipe' on the ends of the boards. I should be able to recoup the cost of the planner by selling the shavings.

Started on the exhaust flanges. "Measure twice, cut once" applies to holes, too! Oops.
 

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Vigilant1

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Can't do much to avoid the 'snipe' on the ends of the boards.
The best approach I've found on similar projects is to make my blanks too long by about 1-2" per end, do the planing, then cut to final desired length (removing the snipe).
One big deal for accuracy is to keep the edges very square. It's tempting to smooth them over or even radius them with a router. You don't want to do that.
Looking good!
 

Hawk81A

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In making flanges, I have my best success by boring the large holes first, then the smaller holes, then the outer shape. Dennis
 

Ken Powell

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When using a small portable planer (like a 12" Delta) apply a slight upward pressure to the board as you feed it into the planer and then do the same thing as the board exits. Using this method I hardly ever get a snipe. That being said, I will plane first and cut to length.
 

TFF

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This is pretty helpful, but I’m the type that has to make them long and cut it off.
 

TiPi

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Thanks for the heads-up on the idle speed! (Another nugget of info.) Yes - when I was taking the back cover apart, I was surprised at how small the internal oil passage was, compared to the size of the filter and the oil cooler. I'll add that to the list of things to get base line data on. (rpm vs oil pressure)

For the tractor installation, I won't know what I have to work with until I pull the engine apart.

If I did a pusher installation, I agree, there is enough material on back cover to machine clearance for a thrust bearing.
bl_dg, I wouldn’t worry too much about the thrust bearing. As long as you have about 5mm of a contact annulus between the crank and the bearing boss with clean & flat surfaces, it will work. The oil film formed by the speed difference of the rotating crank face to the stationary boss face will create a hydro-dynamic film that can carry surprisingly large loads. Compare the surface of the thrust bearing to the surface of the big end bearing and they are not that different. The load on the big end is over 10 times larger than the load on the thrust bearing.
 

speedracer

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Got the first club planed down square. Can't do much to avoid the 'snipe' on the ends of the boards. I should be able to recoup the cost of the planner by selling the shavings.

Started on the exhaust flanges. "Measure twice, cut once" applies to holes, too! Oops.
I have a cabinet shop and have worn out a few planers over the years. To eliminate snipe, pick up on the end of the board as the other end exits the planer.
 

bl_dg

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Thanks for all the tips on the planer. I’ve got plenty of ‘free’ wood (recycled pallets), so I’ll just go with longer boards and trim to size. On the final pass, I run the club through all four sides, and then feed again from the opposite end, all four sides. Square and consistent within thousandths.
 

bl_dg

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bl_dg, I wouldn’t worry too much about the thrust bearing. As long as you have about 5mm of a contact annulus between the crank and the bearing boss with clean & flat surfaces, it will work. The oil film formed by the speed difference of the rotating crank face to the stationary boss face will create a hydro-dynamic film that can carry surprisingly large loads. Compare the surface of the thrust bearing to the surface of the big end bearing and they are not that different. The load on the big end is over 10 times larger than the load on the thrust bearing.
Yep - not too worried about it. I’ve got to get a test stand built and get the engine running first!
 

bl_dg

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Decided to start stripping down the engine so I can figure out how to mount the test clubs. I went to take the fan shroud off, but one bolt was under the cylinder head. Well, under the breather box on the side of the head. (Odd construction sequence.)

I should be able to make a hub that will bolt to the flywheel, and I can clamp the test clubs to the hub.
 

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bl_dg

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Got the engine stripped down. Now to rebuild for testing. Should be able to get some improvements on the intake - the stock intake has 4 90-degree bends.

I was at the WPAFB museum a few weeks ago and found the perfect project. Seeing as how the ULTRA UAV has shown that 2 of these engines can carry a 100 kg payload, all we need is a more pilot-friendly aircraft - maybe a two-place airplane that could be scaled down to carry one person...
 

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Vigilant1

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... all we need is a more pilot-friendly aircraft - maybe a two-place airplane that could be scaled down to carry one person...
The MicroMaster!

Projected specs are here.
With two 28 HP engines and fixed pitch direct drive props, it looks possible to go 140 mph TAS at 6000'MSL burning 4 GPH. Safe single engine climb also looks possible up to 6000 msl. But:
- I couldn't make the numbers work (esp single engine climb) at less than 28 HP per engine.
- Centerline thrust is a big advantage in this application if safe SE ops are a priority.
- Sufficient span is important. At 770 lb MTOW, it looked like a 26’ span would allow safe single engine climb. More span would reduce induced drag and be even better in this flight regime.
 
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bl_dg

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The MicroMaster!

Projected specs are here.
With two 28 HP engines, fixed pitch props, it looks possible to go 140 mph TAS at 6000'MSL burning 4 GPH. Safe single engine climb also looks possible up to 6000 msl. But:
- I couldn't make the numbers work (esp single engine climb) at less than 28 HP per engine.
- Centerline thrust is a big advantage in this application if safe SE ops are a priority.
- Sufficient span is important. At 770 lb MTOW, it looked like a 26’ span would allow safe single engine climb. More span would reduce induced drag and be even better in this flight regime.
But with the Mini-Bronco, I could scan for ground targets. 😉 Anyway, good weather this weekend, so I hope to make more progress on the engine.
 

Vigilant1

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But with the Mini-Bronco, I could scan for ground targets. 😉 Anyway, good weather this weekend, so I hope to make more progress on the engine.
You'll find out why it's called a Bronco when you lose an engine on climbout at 60 kts. ;)

Blane.C was also mulling over a 3 engine design: the Tri-mower (kinda a Bronco + 1)

Good luck on the engine, keep us updated.
 
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