Hatz Biplane Association

The Hatz is still over at Brodhead but I will check and provide whatever data I can get if there is really an interest.

The downside to motorcycle type wheels is they can handle very little side load. If you swerve on landing(not uncommon in a taildragger) it can put a bunch of side load on the wheel causing it to collapse and thus a prop strike and groundloop. Happened to my neighbor on a Pober Jr Ace. He reinforced the wheels but frankly I don't think that really solves the problem. Just my opinion.

Bill

Hi all,

We agree to Bill's concern about sideloads. We heard thi from other sources as well. However, the main concern is when you are landing on paved runways - on grass it should not be a problem. However, We would definitively not recommand those Aerodrome "vintage look" motorcycle wheels: This would be dangerous an a 1700 lbs Hatz.
Concerning our wheels, we are still searching for the right 130/90 x 16" (rim dia) tyres. We now found a Metzeler tyre, which we will investigate for applicance. On our last stay at Brodhead we found, that Mehlin's tyres had the same problem as we discovered with our Baracuda tyres: they don't run concentric (they show some "jimmy"). As soon as we have found the right tyres, we will post the result.
Hans & Sam, H.C. #78, Switzerland

I can design a wheel/hub assembly to carry the side loads. If I have the details of the "Speed" type wheels it can be done.

The Aerodrome wheels are not design for the gross weight of a Hatz as stated above, they would be marginal on a Pietenpol too. Why I designed my own.

Please let me know if anyone comes up with any info on this, would like to design & build a few sets, even make drawings available too.

.... exciting!

Hi,
Although I am using 6" wheels on my CB-1, the large wheels definitely have a place on our type of plane. I see the conical discs as being the difficult part of making the large diameter wheel. Does anyone have any thoughts about using a composite disc (graphite fiber) with a metal hub? Seeing how heavy the metal wheels are may make this worth looking into.
Al

That is sure an option. Strength and weight are a factor, then cost. Today with modern materials and CNC machines you can make any part. Would like to see what one looks like and how they were made, then go from there.

Engineering them is not an issue.

Yes, very exciting. Hans & Sam, could you post some images and perhaps dimensions of your wheels? I am very interested in this discussion.

Nick

Here is a reply I received from Hans & Sam:

Dear Nick,

We understand well your enthousiasm about those slim high pressure
wheels. We got also excited, when we first saw Mehlin Smith's Warner
Hatz with such wheels!
However, in the meantime we are a bit concerned about the sideload
capability of such wheels: Some pilots are telling nightmares what can
happen when landing in strong crosswings and others tell there is
absolute no problem. We think it is mostly a matter of inertia loads
and a real problem is anyway only on paved runways!

The only data we have on hand (we don't have any drawings) are:

Wheel (tyre) dia: 24"
Rim dia: 16"
Tyre width: about 4"

As you know, they were build by Dick Fischer from California and two
friends at Brodhead, WI. They were not cheap to say the least, but
they are equipped with Grove hydraulic disc brakes.

As we noted several times, we still haven't found the smooth tyres we
are looking for. We came no close to a suitable Metzeler, which we
will have to grind smooth.
We bought our wheels with Baracuda 130/90 motorcyle tyres (not
mounted), but the would not fit smoothly. They showed some bad
centering, which yileded in a sort of "Jimmy" (not turning smoothly).
However, this July at Brodhead we detected that Mehlin's wheels didn't
run smoothly as well (he might have the same problem!

There is a Hatz modified to look like a Travelair 4000 flying (I
beleave in California) with Fischer 24" wheels and this has Dunlop
120/80 tyres mounted. As far as I know, this runs nicely.
However, Mehlin turned from 120/80 to 130/90, because he wanted some
more energy adsorption. The static load capability of 120/80 tyres is
about 250 kg whereas the 130/90 is about 280 kg (it is difficult to
determine what's needed, so, the more the better).

We are also in contact with PUR SANG Aero Historic of Argentina. They
are building tyres for their 19" (rim) wheels for their Avro 504. The
plan to build a tyre for the Gispy Moth, which has a 15" dia rim
however. Ron Souch of England (the Gipsy Moth restorer par excellence)
is offering spoked wheels with 15" rim for the Gipsy Moth (which is
much heavier than a Hatz).

Nice. Is the inside rim a casting? ... spoked? Is outside an aluminum shell?

The issue with side load failures, does anyone know of the construction?

Thanks, great start.

Blue Skies,
Keri-Ann

There is a cast aluminum hub, which carries the brake disc. The aluminum discs are stressed skin and hold the wheel together. There are no spokes - this is a patented bendix wheel!
a couple of more pictures.

Hans & Sam

Cool. So when do deliveries start, Keri-Ann?

Nick