# Reliable??? I've heard they are.

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#### Jman

##### Site Developer
Does anyone have experience with the half VW engine? I have been considering building a Hummelbird which uses the half VW engine and I was hoping to hear some comments on their reliability and ease of building. From what I understand you need to actually saw the block in half and weld some counterbalances to the crank shaft. Any comments?? I've heard they have a good record, and I really really love that little hummelbird. Thanks in advance.

JakeC

#### lou mc carrell

##### Member
1/2 vw

jake,
i have no direct experience, but did a lot of research for a legal eagle ultralight. what i discovered is it ain't worth cutting the case in half! basically remove the back two cylinders, cut the cam in half and have the crank redone. also, a friend of mine experienced trouble with the cam gears. i can get you the details later, but it was squeeking and it had to do with a new cam gear with a used crank gear.
i have friends using them, i can ask around and see what they have to say.
lou

#### revpeach

##### New Member
I've built two half VW's. There are several ways they can be built. Some cut the case and other use the whole case and just plate off the extra jub and push rod holes. Both conversions require the crank and cam be cut. The crank is the most difficult because it must have counter weights welded on and then rebalanced. I ordered my cranks from Great Plains Aircraft. They did all the work and work fine. The only other difficult is making the heads. I built mine from scratch but half heads can be purchased already done.

Wayne Peach

#### Jman

##### Site Developer
That would be great if you could ask around Lou. I've narrowed my choices of aircraft down to three: Cozy MK IV, Mifyter, and Hummelbird. Of course as I write this all the other designs on my list of 15 are screaming, "That’s not what you told me!!" Anyway, I digress. The Hummelbird is very attractive to me but the thing is, I do not believe you can use the full case 1/2 VW on it. I do not know this for sure however. I believe Morrey Hummel sells completed engines so I may ask around to find out how complete and well put together they are. I noticed that Great Plains also sells U assemble ½ VW kits. I'm not for sure that the Hummelbird is in my future, but hammering out the details of the engine my help me make up my mind. Thanks for the response guys.

Jake

#### lou mc carrell

##### Member
1/2 vw

We have our meeting this wed, i'll check on the details of that cam gear problem. in the mean time, have you checked out the legal eagle? i have one under construction. legal ultralight (most ul's wind up going overweight). it uses a 1/2 vw, case not cut.
lou

#### GHvizdak

##### New Member
Have a friend that just completed a Hummelbird with a 1/2 VW (full case).
Will be transportiing to Local airport for test run soon. Looks like a rocket. Will post picture later. Do Not cut the case, bearing journal will not take crank stress. Have a 1/2 case here with damage to rear bearing journal only after 30hrs. on a Sparrow UL.

Geo

#### Jman

##### Site Developer
Does anyone know the weight difference between the full and half case? I wonder how it will affect the CG. I imagine it sticks out quite a bit more with the full case, unless it is mounted differently. Hmm.. Just curious.

I really like the hummelbird because it appears to be very simple and inexpensive and would be a great learning experience. It's very attractive and quite a good little performer for its size. My wife doesn't want to even hear about it because it only has one seat though.

Jake

#### GHvizdak

##### New Member
Hummelbird

Guys,

Here are a couple of photos of Bob Dalesio's Hummelbird. Bob lives in Washington, PA and has no computer, we just transported his "Bird" to Toronto, OH, where it will be based.

In my hanger and will be test flying as weather permits. Also in this hanger is a Carlson Sparrow UL ( with a TEC 1/2 VW) and a 1941 Taylorcraft BL-65, currently apart cabin forward for some restoration and a top end.

Soon Bob's plane will be in his own hanger ( he has become a member of our airpark).

Will keep you all informed of our progress. Still having problems developing a starting sequence that works with these engines.

We do a lot of "arm" exercises.

Geo

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#### GHvizdak

##### New Member
Hummelbird Picture2

Picture2

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#### Jman

##### Site Developer
Thanks GEO. Have others reported problems starting their 1/2 VW I wonder? I look forward to hearing how the testing turns out.

Jake

#### Craig

##### Well-Known Member
Starting the Half-VW

Usually, we leave the ignition OFF, airplane tied down (it has a release hook above the tailwheel), throttle full open. Prop it through two or three times, then retard the throttle to just cracked a bit, ignition ON. Should start on the first pull.

Ours is a conversion from a Mosler 2165cc, now 1082 cc, Bosch distributor, modified throttle body injector.

Good luck with yours!

#### david shirey

##### New Member
I have a 1/2 v w built by scott carlson hummel design workmanship seems excelant but only have 15 min on it on z max performance is great but have oil cooling problems to work out as soon as weather gets to open cockpit temp i will start and report again dave shirey

#### Jman

##### Site Developer
Please do, I'd love to hear how it works out for you.

Jake

#### david shirey

##### New Member
1/2 v w

flew with new design cowling made little diferance oil temp was 230 after 5 min in air not sure what to do next am working on ground running trying to break engine in maybee loosen clearence on engine up trying to not add oil cooler maybee richer mixtuer?

#### Jman

##### Site Developer
Hey David,

You might want to open a new thread to get some input on troubleshooting your problem. Some may not notice your dilemma buried in this thread.

I look forward to hearing about how this problem gets solved!

Jake

#### Wrongway John

##### Well-Known Member
Although it’s an old thread, I had some comments I wanted to add for those considering the 1/2 VW, and also wanted to answer some unanswered questions.

Does anyone know the weight difference between the full and half case?

Have others reported problems starting their 1/2 VW I wonder? I look forward to hearing how the testing turns out.
Bill Spring generally gets his started in two to three hand props. Those that don’t use a magneto, and are going with a Leeburg ignition state that they start even much easier with it.

Do Not cut the case, bearing journal will not take crank stress. Have a 1/2 case here with damage to rear bearing journal only after 30hrs. on a Sparrow UL.
The case may be the weakest link to a VW, full or 1/2 VW case, I dunno, but I do know that many go well beyond those hours. Perhaps something wasn’t done right with this case. David Roe had the cut case, and went nearly 900 hours on his 1/2 VW before the case finally developed a crack in it. One problem with the 1/2 VW engine, is, many report vibration problems occurring at certain rpm’s, generally around 1800-2,000, so one needs to avoid those rpm’s. After one has added the additional counterweights to the crankshaft, I think some say additional weights may need to be added to around the prop area to get the vibration out if one desires to do so. After going 900 hours on his 1/2 VW engine, David Roe went to a 4 cyl VW, as well as did Bruce King. Bruce went to it on account he’s a fairly good sized man, and not sure if Roe went to it for the additional power or if it was because of other issues he had with the 1/2 VW. With the nickies cylinders now out for 1/2 VW engines that can bring the horsepower up to around 45, power shouldn‘t be the issue with the 2 cylinder Hummelbird, I wouldn‘t think. The nickies also run much much cooler, so heat is no longer an issue. The cylinders are rated at a 2,000 hour TBO, and the engines come in about 4-6 lbs lighter than other 1/2 VW engines. The major drawback is price, they are quite steep, but seem well worth it to me for the amount of problems they solve.

If anyone else has experience with the 1/2 VW, I hope they comment on it, since I will be starting my Hummelbird project this fall, and plan on going with this engine, running the nickie cylinders.

WJ

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#### MMM_66

##### Member
Hi,
All of you guys interested n the 1/2 Vw , I have group in the Yahoo forum called HalfVw_Engines. Lots of great people in it and you can generaly get questions answered with in a short amount of time.
Here's the link below..

http://groups.yahoo.com/group/HalfVw_Engines

MM

#### corbenpilot

##### Well-Known Member
Hey 1/2 VW builders

I'm a long time builder/flyer and I'm presently working n a new project a sort of rip off of a Legal Eagle a friend of mine started but had too many other projects to finish.

My first intro to the 1/2 VW was ten years ago in Ontario Canada where a guy had one of these mills purring our in front of his high wing homebuilt. The darned thing purred like a petted kitten and the owner swore by the design. Since then I've heard all manner of hangar talk, both good and not-so-good as to the engine.

I'm a little luckier than most folks I guess as I have a lot of engine building experience coupled with close friends in the engine machine business. I figure I should be able to overcome most obstacles. I have a '69 Beetle engine that I'm getting ready to tear down and get to the basics of inspection and ordering what I need in the way of parts and machine work. As yet I do not have any plans for the 1/2 conversion and I'd be appreciative of anyone that could steer me in the right direction.

I do beleive (remember) that the cases are magnesium and there are but a few welders in my area that would consider welding on those cases. This for the mount plate that I see in most photos of the 1/2 VW.

Or is the rear mount portion of the case fastened in another way?

Love to hear from all you 1/2 VW BUGggers!
Don corbenpilot@excite.com

#### wally

##### Well-Known Member
I believe the folks at Hummelbird sell 1/2 VW plans.

As far as welding magnesium, my not-completed attempt at building a 1/2 Vdub got easily beyond this. All I did was cut some strips of the discarded part of the case as well as 2 half circles to fill the good half case. The strips were a about 1/4 by 1/4, pretty chunky and were not very long. A guy with a TIG welder then easily stuck it together for me. He used pliers to hold the strips and used them as filler to weld a piece into each case half to fill the area where the cylinder hold got cut through. It looked just fine. It took him about 15 min. The heads are aluminum. A single stock head can be cut in half and make a left and a right head.

For my case cutting in half and cutting a head in two, I used a HAND HACKSAW! It took a while but I did it. I was younger and broke at the time!

The case is cut on the far side of the center bearing. The engine uses the pulley end of the engine - the end by the bumper of the car. A flat aluminum plate is fabricated and screwed across the end where it was cut. The case must then be chucked in a big lathe and the cut end faced off smooth so the plate will sit flush. A LH magneto is driven by the crankshaft right on the cut end of the crank, mounted on the flat plate. A coupling must be made to connect it to the crank.

Best wishes,
Wally

#### Ace_Plumber

##### Well-Known Member
Previous posts seem to answerer most questions about th 1/2 vw engine.as for myself I would not use the full case on the H.B. You use the stock mounts in this configuration and that doesn't leave room for oil filter, oil cooler, engine breather/oil separator. I got lucky and found my engine in the classifieds in the back of Kitplanes magazine for $1300 bucks. It only had 3hrs.run time on test stand.A good start but had to tear it down to change from bed style engine mounts to rear mounts.(Not much room in the H.B. cowling). As for oil temps. I would recommend an oil cooler (small from motorcycle). The 1/4 tubing wrapped around the Y intake seems Micky Mouse to me. my oil cooler is about 4"X8" I have trouble getting enough heat into the oil. On a day with 90 F ambient temperature my oil temp. gets to 140 F after 5 min. full power run up on ground. I think if I were starting to build up a new engine I would start with a new case not one with ???? hrs. on it already.This could explain why some crack sooner than others, the case could have been thrashed by a lead foot driver or driven lovingly by Granny. As for starting the engine, I have a primer pump (cheap from Great Plains Aircraft Supply, less than$15) I give it two or three squirts, open throttle about 1/4" from closed and flip the prop. it usefully starts by the third pull. I have the Zenith updraft carb. with crab heat box. (Works fine and is easy to adjust.) Ignition is Fairbanks Morse two cyl. Tractor magneto. Not a very hot spark,so you have to gap the plugs to .16. They run clean and I haven't had any problems with fouling so far. Well thats my two cents worth. I pass it on to you, now I have no cents LOL. Best of luck to you.