Login Form

Welcome, Guest
Username: Password: Remember me

TOPIC: Engines for the Quickie

Engines for the Quickie 10 years 10 months ago #754

  • haiqu
  • haiqu's Avatar
  • OFFLINE
  • Expert Boarder
  • Posts: 118
  • Karma: -2
.
So, you want to build a Quickie, or your old engine has had it's day, and you don't know which engine to fit into it. When researching suitable engines a few years ago I came up with some likely candidates. These days there is an even better selection. Here's the guide.
    WHAT NOT TO USE
1. The Rotax 277 and 377 are fine little engines for powered gliders, and appear to have enough power for the Quickie. But they need a redrive gearbox, use heaps of fuel and it has to be premixed with oil. Skip these. Besides, they're no longer supported by Rotax.

2. Wankel engines periodically pop up with fantastic weight and power figures. Don't waste your time, NONE of these have ever become a real product for aviation. It's all just smoke and mirrors.

3. The Teledyne 4A032 is NOT the engine you want. No, this is not a Jedi mind trick. It really is NOT an aircraft engine. It does NOT have more than 6 hp output. Stop dreaming.
    SELECTION PROCESS
Quickie Aircraft Corporation became aware fairly early that at high altitudes or under hot conditions, their little 18 hp Onan was inadequate. They tried to upgrade it to 22 hp but this modification made the engine unreliable, and their plans to turbocharge it didn't ever happen. If they had, it probably would have been disastrous anyhow.

But there are industrial engines that are eminently suitable. Researching likely candidates in the 25-30 hp range - and you DON'T need 60 hp like some people seem to think - finds a few basic models to consider:

Honda GX670 24 hp @ 3600 rpm, v-twin, $1250.00
Robin EH72 25 hp @ 3600 rpm, v-twin, $1365.00
Rotax 503/582 25 hp @ 3600 rpm, inline twin, $3750.00
Chinese diesel 25 hp @ 3600 rpm, v-twin, $1100.00

All of these should be fine with the Cowley 44" prop specified by QAC for the 22 hp engine, or a modern equivalent, and you should get a static turnover of around 3250 rpm. Engine rotation of all these is also the same as the Onan - clockwise, as viewed from inside the cockpit.
    RATIONALE FOR THESE CHOICES
1. Honda has a long and very clean record of manufacturing reliable engines. The newer GX690 might be a better choice once generally available. Apparently no fuel injection option.
2. The Fuji Robin (Subaru) engine has a successful history of aviation use in the early ultralight days, and they make good engines.
3. This is an odd one, but I think it would work well. Using a Rotax 503 or 582 without a redrive below 4000 rpm should yield relatively good fuel consumption, weigh about the same as a 4-stroke and last a long time between overhauls. The downside is needing to mix oil into the gas, but it has a major plus of being an aviation engine, and on later versions having dual electronic ignition. I would even be tempted to try a Rotax 635 ski-doo engine (rated 25 hp @ 3850 rpm) if one could be found with very low hours. Note that since all of these engines idle at 1800 rpm or so you might have to shut it off immediately after touchdown to avoid coasting too far down the runway.
4. The Chinese make diesel v-twins with about the same weight and performance as the Honda and Robin petrol engines. If you're operating out of an airfield with Avtur available you could run one of these engines. And let's face it, even the Chinese couldn't screw up a diesel, they're dead simple. Downside is finding mechanics who will touch them for maintenance. Upside is they're relatively cheap, in the vicinity of US$1100.00 landed.

Not really suitable for small airfields with limited facilities unless you're planning to simply putter aroud the same patch and not go anywhere, and don't mind bringing your own fuel. This particularly applies to Australia, where Avtur is only available at larger GA airfields, at which a 95.55 airplane is forbidden to land. Of course if you built under 101.28 and have VH registration and a regular PPL and the correct instruments, go for it.
    WEIGHT AND BALANCE
The Onan engine weighed 80 pounds. Most replacements will come in at 90 to 100 pounds with starter motors. Be sure to do a proper weight and balance using a known good scale, and make your airplane's individual chart up to suit that airplane. Using the one in the Pilot's Operating Handbook isn't even valid if you use the Onan, because everyone's airplane is individually built. The maximum gross weight you should be flying with these engines is 520 pounds (revised from 480 pounds in the POH, see QAC newsletter #17). Stay alive long enough to fly and enjoy your creation!
    CAVEATS AND FINAL WORD
Any engine is going to lose 6 hp for every 1640 feet of altitude unless it's turbocharged or otherwise compensated for high altitude. Engine manufacturers generally rate their products under ideal conditions. Even then their data sheets contain warnings that production samples will be within 85% of the rated specs. So your 25 hp engine just became a guaranteed 21 hp, at sea level and 60 deg. F, and only when brand new.

Apart from the diesel engine, the examples above were not priced with fuel injection. Choose the model with these features for the best "bang for your buck", if available. That way there will be less messing around preparing the engine for aircraft usage:

a) Fuel injection should get you an extra 3 hp, no carb ice problems, no choke, easy start, electronic ignition and automatic altitude compensation. It's well worth the extra money.
b) For 2-strokes, get oil injection for added safety and convenience.
c) Oil pressure sensor (not level sensor or "safety cutoff"!)
d) Tapered power shaft (not keyed or splined shaft!)

Finally, expect to have to throw away some heavy or suspect standard parts and replace them with airworthy equivalents. Especially fuel lines, baffles, oil coolers and exhausts - although generally you can buy most engines as a replacement part without the exhaust.

If you're really on a tight budget, consider a half-VW conversion. The cylinders probably won't fit inside the standard cowling, but you'll get 33 hp with dual carbs and enough have been built to know they work well. With Leonard Milholland's "Better Half" conversion you don't even need to cut the crankcase.

With the above information, you should be able to get a Quickie flying in no time.
Last Edit: 10 years 10 months ago by haiqu.
The administrator has disabled public write access.

Re:Engines for the Quickie 10 years 10 months ago #758

  • bnther
  • bnther's Avatar
That's a nice little write up on the engines. I didn't know about the Chinese diesel.

A quick question about the V-twins. Did you take into consideration the centerline of the crank with regards to how far the motor extends upwards? The crank on those engines is at the very bottom of the motor and what I'm wondering is whether or not the motor will extend upwards too far.

I like the idea of the V-twins, simply because the one I was looking at came with a starter. I really don't care for the 'hand-start' of the VW's. However, I do like the torque of the 1/2 VW. I'm also thinking that the crank on a 1/2 VW is probably going to be a heavier duty than the crank a on V-twin.

I dunno. Food for thought anyhow.
Last Edit: 10 years 10 months ago by bnther.
The administrator has disabled public write access.

Re:Engines for the Quickie 10 years 10 months ago #759

  • haiqu
  • haiqu's Avatar
  • OFFLINE
  • Expert Boarder
  • Posts: 118
  • Karma: -2
These engines are typically 475mm (18in) tall, with the crankshaft center at 1/3 of that height. Any new engine is going to require a bespoke cowling and mountings, so I honestly didn't consider this a problem. You'll notice that the Quickie fuselage is taller than it is wide, so a v-twin shouldn't cause any undue concerns.

VW engines are a poor choice since the cylinders jut outside the cowling on those I've seen. And I agree about hand cranking being undesirable, along with lack of an alternator for recharging the battery. Both the Fuji Robin and the diesel have fantastic torque figures.
Last Edit: 10 years 10 months ago by haiqu.
The administrator has disabled public write access.

Re:Engines for the Quickie 10 years 10 months ago #768

  • haiqu
  • haiqu's Avatar
  • OFFLINE
  • Expert Boarder
  • Posts: 118
  • Karma: -2
It should be noted that none of the above v-twin engines will be suitable for aircraft use straight out of the box. Typical industrial engines don't have thrust bearings suitable to be pushed or pulled by a propeller, and fuel lines and their fixtures leave a lot to be desired.

Air filters are often larger and bulkier than desirable, and the standard cooling fans and shrouds could likely be replaced with lighter baffles and natural airflow from the aircraft's movement.

Being 4-stroke engines, none of the above need special treatment for the exhaust, so a pair of tuned straight-through pipes should work fine.

Keep it light, strong and simple.
Last Edit: 10 years 10 months ago by haiqu.
The administrator has disabled public write access.

Re:Engines for the Quickie 10 years 10 months ago #775

  • haiqu
  • haiqu's Avatar
  • OFFLINE
  • Expert Boarder
  • Posts: 118
  • Karma: -2
There is one more possibility. The Linimar LX790 20hp engine is the modern equivalent of the original Onan engine. It should drop right in with no changes apart from whatever QAC did to them prior delivery. Unmodified they should be way more reliable than anything QAC delivered.

There is also an Onan P220G which is, again, an almost drop-in replacement, and in fact is the same engine rebadged.

If you can find one, they should be about $495.00 at street (eBay) prices, or you could rip one out of your neighbor's John Deere tractor. ;-)
Last Edit: 10 years 10 months ago by haiqu.
The administrator has disabled public write access.

Re:Engines for the Quickie 10 years 10 months ago #776

  • haiqu
  • haiqu's Avatar
  • OFFLINE
  • Expert Boarder
  • Posts: 118
  • Karma: -2
For a lesser known 25hp v-twin - just like the Onan and Linimar brands, no-one outside of America will have heard of it - the Kohler CH730 is also worth considering. Although they tend to be expensive so unless you find one at a bargain basement price I wouldn't bother.

$1,495.00 and upwards, depending on which variant you get.
Last Edit: 10 years 10 months ago by haiqu.
The administrator has disabled public write access.
Time to create page: 0.212 seconds
Powered by Kunena Forum