HP VT21 worth using?
 

I bought an HP VT21 in the 1980's. I never got a chance to build anything to put it in. It is 100% complete, box, instructions, etc. I have never even started the engine. I'm wondering if this engine is worth using? Does it have any collectable value that would go down by being run? Bottom line, should I sell? And if so, does anyone have an idea what it's worth? Or should I find a kit I can build so I can use it?

RE: HP VT21 worth using?
 

Chuck:

The VT-21 is supposed to be a very nice running engine, but heavy for its power.

If you put it on a "Cub type" plane it should do well, but it's not going to be much more than a "Fly around the airpatch" engine.

Collectors? The last one I saw change hands was the VT49, the bigger version, and it went for $150.

You are aware the VT21 and VT49 atre both available brand new, made in the USA?

Bill.

RE: HP VT21 worth using?
 

I've also got a VT21 I bought in the 80's and although it did some time on an airboat, it never saw any airtime before I put it away.

I got it out a few months ago and found that the bearings were rusted to hell and back despite using an after-run oil (should have used castor oil eh? :-) so I'm in the process of rebuilding it.

From memory they're not awfully powerful and (unfortunately) don't have the traditional 4-stroke attribute of liking to swing a big prop slowly. In fact, if I recall correctly, they take about the same size prop as a good 21 two-stroke but don't spin it nearly as fast.

They also don't idle particularly well.

But hey, in a nice high-wing cabin model (perhaps a (semi-)scale Piper Cub or Citabria they'd be a quite nice little mill.

RE: HP VT21 worth using?
 

I have a VT .49 that will go in my wife's Sr. Kadet, and I plan to get a VT .21 for my Quaker Flash (67"). I hear they buzz along like a sewing machine, and I think they will do fine in those slow fliers.

RE: HP VT21 worth using?
 

The newer versions made by MECOA are more powerful, Randy enhanced their breathing ability, than the originals of both the .21 and the .49, a Sig LT .25 would be a perfect plane for it.

RE: HP VT21 worth using?
 

I have the .21 and .49 and the .25 car engine. They are not super powerful but are quieter than anything available. They idle fine and are quite docile. I use my .49 on a .40 sized photo plane and it is absolutely perfect for a slow flying application. They are so quiet that I had an electric starter on mine and was wondering why it wouldn't start after 5 seconds. I pulled the starter away and it was running the whole time and I couldn't tell! The new ones have roller bearing heads and I've retrofitted all of mine with these. A really neat engine!

Max

RE: HP VT21 worth using?
 

Thanks to all for the input. It sounds like it's worth keeping and using. Now I just need to find the perfect "Fly around the airpatch" plane to build. Something with a 67" wingspan sounds a bit too tame, but as was suggested, a "cub type" works for me.

RE: HP VT21 worth using?
 

.14 slow poke or Clancy Bee series?

RE: HP VT21 worth using?
 

Slow Poke is a good possibility. Not crazy about the Bee planes.

RE: HP VT21 worth using?
 

Very nice little engine, picked one up at a swap meet the guy said he could not get it running,he just did not have it plumbed right
very nice ticks like a watch but as stated not a lot of power would be fine for light scale etc, I sold mine to a modeler in the UK for
$100 US , sort of sorry now I sold it. Along the same lines of nice but not a powerhouse I picked up a new enya 40 4 strk open rocker
arms quiet with just an exhaust stack no muffler neat at an idle you can hear the valves , it will not go in a plane I do not want to take
the chance of a "mishap" and messing up that nice valve train martin

RE: HP VT21 worth using?
 

Hello; I have one of those VT21's, I last saw it fly in a Dynaflite Piece of Cake. I couldn't get it to idle below 3300 rpm's, but it would run happily, and very quietly, but you would have to fly the tank out because it wouldn't shut off. I tried it on my speedy bee and it wouldn't get it off our grass runway. I would say run it, it is a well designed well made engine with some clever ideas with the rotary valve.

Diesel Dan, I have one of those open rocker Enyas' too, runs great, very quiet. I haven't mounted it into a plane yet.

RE: HP VT21 worth using?
 

Thanks Dr. I'm working on a list of candiate planes to put it in.

RE: HP VT21 worth using?
 

I too use the VT .21, and love it. I have 10 or so 4-strokers, and this one is one of my very favorites. I had it on a cub first, but it has now logged many hours on a 40" Lazy Bee that I have set up for duration work. (I want to have the Lazy Bee with the longest flight ever) On this Bee, I have tried two different 2 stroke .10's, then a surpass .26, then a FS .20, but none could come close to the low fuel consumption of the HP .21! I am only up to 3 hrs 35min so far, but the development continues. My engine was one of the original Austrian ones, but all parts from Mecoa I have bought have fit and work nicely. I use a 10 inch prop for duration, but this engine likes about a 9x4 or 9x5 and 15% fuel, and will spin nicely and safely (over 13,000 rpm. no valves to float!). When flying with this engine, people have actually asked me what kind of batteries my plane was using! It is that quiet. I think this engine is overlooked and underrated. (details of duration plane upon request) P.S. Lazy Bees forever!

RE: HP VT21 worth using?
 

I also have a new(old) VT21 I'm going to put on a Lazy Bee I am building.

It seems to me that I may have to widen the fuse/firewall a bit for the engine mount. Did you have to do that? Also, the VT is a big engine in size. Did you lower the position on the Bee so it didn't stick up too far?

Thanks!

Joe...

RE: HP VT21 worth using?
 

How many ounces of fuel were on board with this 3.5 hour flight???


Francis

RE: HP VT21 worth using?
 

These old HP VT-21 4stroke engines was manufactured in Hirtenberger Patronen-Zundhutchen und Metalwarenfabrik AG, Hirtenberg, Austria.

These engines was smallest 4stroke engine at marked and was released in 1983, are not sure when the production was ended.

The power are not big, 3.463 cc, 0.238bhp at 12250 rpm. But it run faster than poppet valve 4 stroke engines.

The engine are old, but not important, all works well so long you take care at engine. And do not worry about you flies with old engine, I am using my Webra T-4 from 1980 and works well as new and a lot of peoples around me when i am running the engine, some of them said to me, why engine has timing belt..:)

Cause the HP VT-21 has higher compresion ratio at 10.5:1 while OS FS20 has lower compresion ratio at 7.2:1 , but OS FS20 are more powerful in effect/volume. More compression ratio=less fuel , it is a problem if more compression ratio, fuel will detonating, there is difference combustion camber in each engines and has own compression ratio as engine constructor has tested and found which compression ratio are suitable for this engine.

Jens Eirik

HP VT.21 on a Cub?
 

What Cub did you have it on? What was the wingspan? Clipped or regular? How did it fly, did it have enough power?

it sounds to me that, that engine would like a longer prop

Jim

Whoowy, 219 bucks for the bushed rotary valve version.
https://www.mecoa.biz/shopdisplayproducts.asp?id=45

VT .21 SPECIFICATIONS Displacement .21 cu.in. (3.5ccm) Bore x Stroke 0.654 x 0.63 Power .35 hp RPM Range 2500 ~ 15,000 Weight 9.5 oz Prop Size 8x5; 8x6; 9x5; 10x4 Prop Nut Thread 1/4" x28

Check out the 25: http://www.mecoa.com/hp/vt/25.htm?id=2115