# "Micromaster"-- Centerline twin using small industrial engines

### Help Support HomeBuiltAirplanes.com:

#### blane.c

##### Well-Known Member
HBA Supporter
Thanks. The hoses from the valve covers appear to be crankcase ventilation to me not oil return.

#### Sockmonkey

##### Well-Known Member
The DA-11 had the upright B&S 18 HP engine, and it had a no-so-very-slick bump on top. But, everyone flying these little industrial V-twins seems to do it this way. They see the ugly as well as I do, and they have chosen this mounting option anyway. I'd have to know an awful lot to do something different.
The ugly bump isn't hard to make pretty. You just need a little cowl styling. Think about how the old-school roadsters look with the big blower air scoop on top of the block. You could shape it so it looks like that, and actually provide ventilation on the heads where you need it.

#### Vigilant1

##### Well-Known Member
The ugly bump isn't hard to make pretty. You just need a little cowl styling. Think about how the old-school roadsters look with the big blower air scoop on top of the block. You could shape it so it looks like that, and actually provide ventilation on the heads where you need it.
Yes, the existing cowls for these 810cc engines generally do this: A bump for each cyl head with an opening in the front of each for cooling air. It can be made to look okay.
The SE33 engine package (which is the Vanguard 810cc vertical shaft engine turned horizontal for use in the SD-1 acft) has the prop driven off the fan side of the engine (the normal "top" of the engine as fitted in a mower). Mounted this way, the exhaust side of the head is at the rear of the airplane, so the incoming cooling air must be routed to the back side of the cylinder to reach the critical exhaust side fins. From that perspective, it is not an ideal situation (though I'm sure they had other considerations that made this seem preferable to them).
Dimensioned line drawing of B&S 810cc engine (Professional Series). I think the layout, dimensions and mounting holes for their Vanguard engines are nearly identical.

#### blane.c

##### Well-Known Member
HBA Supporter
I wrote SD-1 asking about the engine (EFI) , they claim it is not a Vanguard. I did not foresee this denial so did not to think about calling it a Briggs and Stratton or some other name they may have in Czechoslovakia. But I am wondering if it may be a Chinese knockoff?

#### blane.c

##### Well-Known Member
HBA Supporter
Prices for comparison including engine kits

#### blane.c

##### Well-Known Member
HBA Supporter
The SD-1 is interesting, the cockpit is 21 inches wide so I would lose skin and clothing getting in and out of it and that is after dieting to the 233lb max pilot weight. But I like much of the concept except it being single engine of course.

#### Vigilant1

##### Well-Known Member
I wrote SD-1 asking about the engine (EFI) , they claim it is not a Vanguard. I did not foresee this denial so did not to think about calling it a Briggs and Stratton or some other name they may have in Czechoslovakia. But I am wondering if it may be a Chinese knockoff?
Here's what one reviewer said:
Starting at the spinner, the propeller is a Helix H30F two-blade composite unit, which is spun by a closely-cowled SE-33 air-cooled V-twin. This 820cc engine is based on a Briggs & Stratton design usually found in industrial applications. It produces 33hp at 3,600rpm, weighs a creditable 32kg, and is fed from a 35 litre fibreglass-PVC foam sandwich tank, located immediately aft of the firewall.
I'm assuming (!) the "820cc" should read "810cc."

Their quoted $6839 does include a mount, prop, spinner, and cowling, but that still leaves maybe$5000 for the engine(?). They've done quite a bit to get it suitable for aircraft: new carb and induction system, modified the lubrication, figured out some baffling that works, figured out the exhaust routing and engine mounting, fitted a prop hub and built a prop extension (I'm still a little concerned about that, but all the Lucioles and SD-1s using these engines seem to do it. It surely places more bending strain on the crank and more strain on the bearings), etc. I guess the price is relative: Their price is in line (/HP) with their other options (Hirth, etc) and it comes with a LOT of the work already done for you. OTOH, if the base B&S engine starts at about $900, then$5000 is a significant jump. But, if we applied an hourly rate to the trial and error business of figuring this out from scratch and fabricating the bits, maybe it's not crazy expensive.
Scott Casler's 38HP 1/2 VW with electric system/electric start will run smoother, run "easier" (28cc/HP vs 24.5cc/HP for the 810cc engine), cost about the same or less ($4600). The 1/2 VW would weigh about 103 lbs, so approx 30 lbs more than the B&S/SE33. 30 lbs is a lot, but the 38HP of the Casler engine is real and usable all the time, the claimed 33HP of the SE33 has got to be for a very short time (takeoff). For the Micromaster, if suitable engines can be bought, adapted, and installed for a considerably lower price ($1.5 - $2k each after all mods?) then the project would seem attractive to me. At$3k-$4k total for engines for a total "normal" available 52 HP and a MTOW of approx 760 lbs, the plane could be an economical single-seat fun flyer that can still safely remain aloft and climb after an engine failure. If engine prices work out to$5K each, then the concept loses a lot of its appeal.

Last edited:

#### blane.c

##### Well-Known Member
HBA Supporter
If someone does their own mods, then $1.5 -$2k total sounds reasonable, if they buy a kit with all the mods in the kit to do themselves then something more and if they buy a engine already done for them $5k is not unreasonable. I think the SD-1 kit at$15,500 is on the surface quite reasonable, only time can tell durability.

820cc 810cc could easily be interpretation or typo. You would need bore and stroke information to be sure.

I like your concept how far are you on the plans? Engineering?

#### blane.c

##### Well-Known Member
HBA Supporter
Vigilant1

It is odd idea, the crankshaft end (through the the mower blade) is designed to run into stump and rocks and curbs and what have you without self destructing and the recoil end well .. just the recoil.

#### poormansairforce

##### Well-Known Member
Vigilant1
View attachment 83726

It is odd idea, the crankshaft end (through the the mower blade) is designed to run into stump and rocks and curbs and what have you without self destructing and the recoil end well .. just the recoil.
Actually, it's a great idea since most v-twins just have a pulley on a 1 1/8" PTO shaft that has a 1/4" keyway cut in it vs a 1 1/2" shaft with a taper to carry the flywheel.
Stop the video at 4:16 and 4:24 decide which end you want to hang a prop on.

#### blane.c

##### Well-Known Member
HBA Supporter
I want to hang my prop on the pulley side.

#### poormansairforce

##### Well-Known Member
I want to hang my prop on the pulley side.
Why? That side has a 1/4" key cut into it as well as a step to take it down to 1 1/8".

#### blane.c

##### Well-Known Member
HBA Supporter
The bearing area.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
I'd just stuff the crank in backwards with a prop hub similar to the extended VW prop hubs with the bearing surface. and then lop off the dead weight.

Result = taper hub fitting - and - the big bearing area. Of course there is the little detail of also swapping the cam gear to the other end..........

Gotcha.

#### poormansairforce

##### Well-Known Member
I'd just stuff the crank in backwards with a prop hub similar to the extended VW prop hubs with the bearing surface. and then lop off the dead weight.

Result = taper hub fitting - and - the big bearing area. Of course there is the little detail of also swapping the cam gear to the other end..........
Interesting. It may be easier to fab an extension to house a thrust bearing to carry a long prop hub. Then the side loads would be less.

#### Hot Wings

##### Grumpy Cynic
HBA Supporter
Log Member
Interesting. It may be easier to fab an extension to house a thrust bearing to carry a long prop hub. Then the side loads would be less.
If we were working with a horizontal shaft version this would be pretty easy. A bolt on similar to the 5th bearing for the Corvairs could be developed. Unfortunately the standard mount pattern for a vertical shaft version is not as nice to work with.

But none of this appears to be needed given the history of the existing conversions. Time and envelope expansion could invalidate this observation.