H9 33% Pawnee Tug Conversion

[stevekremer]

OK, got the shock support area reinforced - first picture
Also added ply to the rear landing gear block - second picture
and added ply to the front of the front landing gear block - third picture. Think that should be strong enough?

Now starting to mount engine. New question? The servo cut out for throttle is on top, but the DA120 throttle linkage is on bottom - fourth picture. Where did you guys mount the throttle and choke servos.

Also, The choke arm seems to be in an orientation that will not work. will it rotate?

Steve K

[stevekremer]

More questions. Trying to line up cannisters. I have to move the engine box back to the line (about an inch) to fit the cowl correctly. There is an overlap between cannisters and headers? What am I doing incorrectly? Also, how does one get a bolt through the header with such an angle in the header? See photos. Thanks and Happy New year.

Steve K

[hello82]

hey steve...she's coming along well! can't answer those question for you...but happy new year and look forward to seeing you guys again at your upcoming event. Look forward to seeing this bird in action then too!

best,
Matt

[lenb]

Hi Steve,
You're not doing anything wrong, The canisters were never designed to go in this plane, so we have to modify the header length to get them to work. You want to take off as little as possible to achieve a 1/8 gap between the header and canister.
It will slightly affect the motor performance, but its better than loosing airfields.
The only other way to accomplish the task without cutting the headers is to resolder the headers so they drop straighter out of the motor. This will require the cowl to be cut for the headers to stick out of.

Keep moving along !!!

[lenb]

BTW,
You need to re-post the pictures in post 46. They are not showing.
I mounted my throttle servo inside the fuse under the forward hatch. The choke was a manual one with a rod and clevis sticking out of the cowl bottom.

[JimD]

Steve, I know about the issue with that rear bolt because I have the same headers on the Porter. The fix I learned from DA and others is to use a Dremel tool with a cutoff disc to cut a notch out of the flange so it will slip under the bolt head with the bolt almost fully screwed in. Once the header is in place, you use a "shorty" hex wrench to tighten the bolt all the way.

[Xroadie]

Steve, I know about the issue with that rear bolt because I have the same headers on the Porter. The fix I learned from DA and others is to use a Dremel tool with a cutoff disc to cut a notch out of the flange so it will slip under the bolt head with the bolt almost fully screwed in. Once the header is in place, you use a "shorty" hex wrench to tighten the bolt all the way.

Wow!! Great tip Jim!!

[Xroadie]

I made some headway, as it rained a foot here last week. Lucky for me….my basement stayed dry….as did the Pawnee

I got the DA100 mounted, along with the ignition box and mufflers. We are using pitts mufflers as they were handy. I had to cut the stubs down to two inches to be able to get the cowl on and off over the stubs without cutting a ginormous hole in the chin. I copied the same set up I saw on the tugs at the Horizon Aerotow that used the same power plant and exhaust. I cut two oblong holes for the stubs to poke through.

I also had to cut two holes for the spark plug caps. I was under the impression that I would only have to cut a hole in the left cheek of the cowl, but I had to also cut a second smaller hole in the right side to get the spinner centered and to keep the spark plug cap from rubbing the inside of the cowl.
Here’s some pics.
Pete

[Steve P]

The new tail wheels are here! Gotta love Ohio Superstar. Ordered them on New Years Eve day and when we got home today they were in the mailbox.

Two Maxis. One for the Pawnee and one for the AMR 50.

[Xroadie]

I looked at those online and was unsure which model and size to get! That answers that question

[Steve P]

Pete - I liked the Maxi Leaf a bit more given the slightly larger wheel diameter and heavier gauge steel compared to the Large Leaf. The stance is a bit taller than the stock Pawnee one, while the OS is much much more robust.

Large: http://www.ohio-superstar.com/spring...els/large-leaf

Maxi: http://www.ohio-superstar.com/spring...eels/maxi-leaf

[stevekremer]

Repost of Photos from post 46

Steve K

[Rich Kardian]

Hi Guys,
Went to 1/4 x 28 x 2 inch aircraft bolts for upper spring bolts. Used 1/4 x 28 tee nuts on one side and drilled out for shaft tee nuts on the other side
to make them bushings..By pulling the existing tee nuts out and adding 1/4 inch ply to both sides the 1/4 inch AC bolts fit tight into the existing location. NO problems with the gear at all since. More mods too it than just those also.

Rich

[lenb]

Hi Steve,

I found a photo sequence for doing the canister modification and thought I would post them for you or anyone who is interested.

Len

[stevekremer]

Thanks Len. I am making pretty good headway now. I will get some photos this weekend.

Steve K

[Rich Kardian]

Hi Steve,
In Len's Gear photos, notice the gap between the spring tube and gear fork fitting. Recommend you add a jam nut as there is room for it. If not,
the shaft will un-thread over time. I also replaced all the full thread bolts in the spring assembly with 10-32 cap screws with long shanks and cut
down the thread lengths. Then added 3/8 inch thick bushings between the springs and tube ends to pre-load the springs. No spring compression so
far. Also replaced all the gear bolts with 10-32 cap screws with threads cut down. Now all pivot points are on solid shafts and not threads.
Regards,
Rich

[stevekremer]

Thanks Rich,

I wondered about that and was going to use thread locker. But, I really like the jam nut idea. Thanks again.

Steve K

[kd4jaz]

This is not a new idea obviously.....but all our other threads about it are gone......for now!

I just started working on a commission to build a H9 33% Pawnee for aerotowing. The model will have a DA100, with the standard pitts mufflers. The customer also supplied a tow release mechanism for the tug. Is there anything that needs to be modified or upgraded on the Pawnee for aerotowing? I plan to go with as big a gas tank as possible...100 oz...if it will fit! What about the landing gear...do the springs need to be upgraded?

Thanks for any input!
Pete

I have a DLE 111cc in my pawnee turning a Falcon CF 27x10 wide blade and have towed 55 lb sailplanes with it. (towed the 55 lb before putting on the 27x10 CF) No problem towing a 6M Ventus that weighs 26 lbs to 1000' in about 1 minute. I've got over 250 tows, I did replace the bulkhead landing gear bolts with larger ones. The OEM bolts bent.

Marc