Simple, proven, off-the-shelf industrial V-twin?

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Vigilant1

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The engine conversion hardware came from Spacek, same configuration as the SE24.
Good for them. And hopefully it is providing some useful information on long-term service factors. Igor should probably consider offering them a good deal on a pair of SE-33 XP engines. The drone would get a 20-25% increase in power (handy in single engine mode, which probably establishes their MTOW) and if this delivery service gains traction then they'll build a LOT of hours quickly. Good information and PR for Spacek.

It looks like they even used the Spacek SE-24 cowling. It resembles the head of an eagle in their photo. That trailing link main gear looks substantial given the size of the plane, they are obviously anticipating some bumps.

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bl_dg

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Need to qualify “with support from Briggs”: that is Briggs Europe, not B&S USA. I have been helping them out with some info and advice on squeezing a bit more power out of their engines. They hit the max at around 27hp (dyno test), up from 23hp.
The engine conversion hardware came from Spacek, same configuration as the SE24.
Yes, Briggs Europe. (We have too many lawyers over here.) Do you know what size/pitch prop they are using on the ULTRA UAV?

I plotted the power curve for the 627 engine to calculate the torque curve, then extrapolated it forward to 5,000 rpm. Peak (estimated) power was only 25hp at 4,400 rpm. (non-EFI engine) I can post Excel file later. I think Windracers was using the EFI engine, but not sure. Did you change the cam, or just intake/carb/exhaust tweaks?

I corrected my original post. The Burnelli link went to an article on the Briggs. I renamed the Briggs link and added a link for the Burnelli plane. Interesting concept.

Twins.jpg
 

TiPi

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I can't recall the source for this intel, but AFAIK they are running EFI open loop - no exhaust O2 sensor. Apparently that is an engine configuration available "off the shelf" in Europe.
Correct, a very simple TBI-style (single injector) setup, electronic throttle, open-loop. Ignition is the same Magnetron as the other 38-series engines (fixed timing).

The propeller should be the same as used on the SE24:
Bezeichnung:........................................................Wollner 1160 (Brand)
Anzahl der Blätter:................................................2 (no of blades)
Material der Blätter:.............................................. Holz (material)
Durchmesser:....................................................... 1,16 m (diameter)
Pitch:.................................................................... 15,7° bei 435 mm bzw. 75% Radius (pitch)
Blattbreite:............................................................ 81 mm bei 435 mm bzw. 75% Radius (blade width)
Max. Drehzahl im Stand:...................................... 3600 U/min (max rpm static)


If you extrapolate the torque curve, you need to consider if you simply increase the rpm or if you improve the engine's breathing capacity and therefore shift the torque curve to a higher rpm and/or a higher value. The 38 EFI is pretty max'd out at 3,600rpm, the power curve is already very flat and probably peaks at around 4,000 and below 24hp.
On the other hand, if you can move the torque curve 200 or 400rpm to the right (through porting, valve angles, increased CR etc), you will get a higher hp at the same 4,000rpm:
Torque at 3,600rpm: 45.5Nm
Power at 4,000rpm and 45.5Nm: 25.6hp

Power curve from 38 EFI engine

1663320829854.png

27hp is about the max that this engine can deliver at 3,600rpm and will need quite a bit of work in the heads to achieve that.

The Windracers are looking for more power but with an off-the-shelf engine with minor mods (like the SE24), not major mods like the SE33.
 

bl_dg

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TiPi - Thanks for the info, and for sharing the progress on your engine! (nice little website)

I'm joining the madness and just picked up a new 386447 engine.

386447.jpg

So I took the power curve from Vanguard and put it into Excel, trying to be a little more accurate than my last post. Then, did the math to get the torque. (peak torque 34 ft-lbs at 3,100 rpm) I then did a trendline on the torque curve and extroplated out to 5,000 rpm. Finally, I input torque values to match the trendline, to get the expected horsepower values. (peak horsepower 26 hp at 4,700 rpm)

Yes, its all a big guess-timate, but I was doing this just to 'fact check' some of the claims on the internet. No - I don't expect to be getting 35 or 40 hp out of this engine, or to run it at 5,000 rpm for only 3 more hp.
 

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Bigshu

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I have seen a lot of industrial V-twin conversions over the years but they often seemed pretty elaborate or at least opaque in terms of how much work was involved. I wonder if anyone knows of a relatively simple example that has been proven and flown with little or no modification to the engine itself, just removing bits and bobs that aren't needed for flight, bolting on an existing belt redrive like those from Ace Aviation, then off you go. I am not talking about much power here, just something basic for a low-cost, low-speed flivver.
Hummel is selling a V-twin conversion for around 5K that has enough oomph to power an Ultra Cruiser. The Performance 670 folks offer a conversion based on the Predator V-twin for around 3K, that they claim puts out 43 hp at 4700 rpm. They also sell performance parts so you can DIY the conversion. Interesting website too.
 

TiPi

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TiPi - Thanks for the info, and for sharing the progress on your engine! (nice little website)

I'm joining the madness and just picked up a new 386447 engine.

View attachment 129897

So I took the power curve from Vanguard and put it into Excel, trying to be a little more accurate than my last post. Then, did the math to get the torque. (peak torque 34 ft-lbs at 3,100 rpm) I then did a trendline on the torque curve and extroplated out to 5,000 rpm. Finally, I input torque values to match the trendline, to get the expected horsepower values. (peak horsepower 26 hp at 4,700 rpm)

Yes, its all a big guess-timate, but I was doing this just to 'fact check' some of the claims on the internet. No - I don't expect to be getting 35 or 40 hp out of this engine, or to run it at 5,000 rpm for only 3 more hp.
bl_dg, what you probably find in reality is that the torque curve drops off quite a bit steeper in the OEM configuration due to the restrictive intake system. This is why even light porting and valve seat cutting will have measureable benefits, increasing torque AND move it to higher rpm.
Can I suggest that you start a new thread for your conversion, so we can keep that together. I think you are the first one on this forum with a 38-series (other than K Armstrong), we have a couple of 49-series and 61-series conversions happening. Most share a lot of the same basic info but the 38 is a bit unique in some areas (camshaft, conrods) that need careful review. It would also be helpful if you could state your expectations/gaols for hp and rpm.
 

cluttonfred

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Hummel is selling a V-twin conversion for around 5K that has enough oomph to power an Ultra Cruiser. The Performance 670 folks offer a conversion based on the Predator V-twin for around 3K, that they claim puts out 43 hp at 4700 rpm. They also sell performance parts so you can DIY the conversion. Interesting website too.

Do you mean a half VW? I am not aware of Scott Casler doing anything with V-twin engines.
 

Bigshu

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Do you mean a half VW? I am not aware of Scott Casler doing anything with V-twin engines.
No, I mean Hummel Aircraft. They are offering a V-twin for their Ultra Cruiser, for part 103 operations. They say it's an in house development, with a reduction gear setup of their own make. I spoke to Matt, at Airventure about it, and he assured me it had the power to get me airborne safely in a UC.
 

bl_dg

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I saw the Hummel engines at AirVenture. Two different V-twins with slightly different re-drives. I can't remember if one was a Predator, and what the other one was. I'll try to dig up some photos.

(TiPi - thanks, I will start another thread for my engine build.)
 

Jay Dub

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I'm not certain but the valve covers of the Hummel look like a HF Predator to me. I'm not sure who makes the HF engines. Lifan of China makes some good engines (Honda clones) but these HF Twins don't look like the Lifan Twins. HF Predator single cylinder engines look like Lifans. The new duramax twin looks more like a Lifan twin. The problem with Chinese engines is many companies make many that look nearly identical.
 

bl_dg

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Here are the two Hummel engines. I don't know what brand they are. However, the belt drives are slightly different. One goes down around the drive pulley, the other is entirely above the drive pulley.
 

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TiPi

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Here are the two Hummel engines. I don't know what brand they are. However, the belt drives are slightly different. One goes down around the drive pulley, the other is entirely above the drive pulley.
I think the one on the right is the stock Predator engine (or only mildly modified) and the one on the left is with the high-lift (billet) rockers. They don't fit under the stock rocker cover, so need to use the billet rocker covers.
More info here: Predator 670 Engine Parts
 
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