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-   -   GP Piper Cherokee conversion (http://www.Wattflyer.com/forums/showthread.php?t=73776)

dahawk 05-21-2014 04:20 AM

GP Piper Cherokee conversion
 
I'm in the process of converting a gas Great Planes Piper Cherokee to electric incorporating a set of all metal HK servoless retracts .This will make it a Piper Arrow.

I actually bought the plane used from a buddy and he had already added air retracts. What a project. All I need to do is switch them out. Sounds easier task than it is.

I'm removing the air retracts and the first thing I noticed on the HK steerable nose gear is that besides the normal arm that the servo pushrod/ clevise rides up and down on while the gear lowers and raises, there's a small compression spring attached with a screw to the base.

http://imageshack.com/a/img838/1129/730yt.jpg

Where does the other end of the spring attach to ? What does it do? Is it a centering spring?

Thanks ,

Hawk

kyleservicetech 05-21-2014 04:35 AM

Quote:

Originally Posted by dahawk (Post 948788)
I'm in the process of converting a gas Great Planes Piper Cherokee to electric incorporating a set of all metal HK servoless retracts .This will make it a Piper Arrow.

I actually bought the plane used from a buddy and he had already added air retracts. What a project. All I need to do is switch them out. Sounds easier task than it is.

I'm removing the air retracts and the first thing I noticed on the HK steerable nose gear is that besides the normal arm that the servo pushrod/ clevise rides up and down on while the gear lowers and raises, there's a small compression spring attached with a screw to the base.

Where does the other end of the spring attach to ? What does it do? Is it a centering spring?

Thanks ,

Hawk

Interesting.

One of my club members flies those $$$$ wet turbine models. Up until this year, he used air retracts. After flying with electric retracts this year, he's indicated he will never use an air retract system again.

Don't know what brand his electric retracts were. But, knowing him, they were not cheap, especially when installed in a kerosene turbine model worth thousands of dollars.

dahawk 05-21-2014 04:52 AM

Air retracts work fine but they are a PITA to maintain. Micro leaks are hard to troubleshoot. Tubing and valves all over the place. You need to pressurize an onboard canister, etc. Servoless types have come a long way in a very short time. All metal with metal trunnions and 5mm pins. Slip fit spring loaded oleo struts. Nice.

They now make them for planes weighing 30 pounds. I think the heaviest plane I have is about 7.5 lbs. You do get what you pay for IMO. The expensive Robarts are well? Robarts - LOL I'm good with the HK's for now. Should hold up for my lighter applications.

I don't want to end up paying more for the retracts than I did for the plane.

Adding Exceed 660kv motor ( a 46) and 85 amp esc. Will run 5S.

kyleservicetech 05-22-2014 01:17 AM

Quote:

Originally Posted by dahawk (Post 948790)
Air retracts work fine but they are a PITA to maintain. Micro leaks are hard to troubleshoot. Tubing and valves all over the place. You need to pressurize an onboard canister, etc. Servoless types have come a long way in a very short time. All metal with metal trunnions and 5mm pins. Slip fit spring loaded oleo struts. Nice.

They now make them for planes weighing 30 pounds. I think the heaviest plane I have is about 7.5 lbs. You do get what you pay for IMO. The expensive Robarts are well? Robarts - LOL I'm good with the HK's for now. Should hold up for my lighter applications.

I don't want to end up paying more for the retracts than I did for the plane.

Adding Exceed 660kv motor ( a 46) and 85 amp esc. Will run 5S.

Yeah
When you get to those $$$$$$ wet turbine models, or similar sized units, retract prices go through the roof. :censor: If you've seen a 40 pound wet turbine model land on a grass field, their is no such thing as a greaser landing!

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCHVL
http://www.horizonhobby.com/products...7-30cc-HANP47E

https://www.youtube.com/watch?v=ekbLseR16UY

dahawk 05-22-2014 02:24 AM

Here is the first test of the 120 size all metal HK retracts. Pretty sturdy. 5mm pin to oleo: http://youtu.be/NZfri_eOALA

Now these are $65.00 for the set. Another ~ $20 for the main 130mm long oleos and the offset 108mm long nose oleo strut. Yeah, not in the same league as the Robarts but I think they'll serve the purpose: Taxi to runway, take off roll, rotate, gear up , fly around, gear down, land.

If they hold up, I'll put a set in my EMB-312 Tucano and Deuces Wild.

I do admire those guys with the bottomless pit for a bank account who fly wet turbines. A blast to watch. I'll never get there. Still trying to master the 70mm foam versions. I could add up my entire squadron of 20 plus planes, sell them all and would still be a few thousand short. LOL

Have to travel Friday through next Thursday so I was hoping to get some of the conversion done before I left. Hopefully tomorrow, I'll get the motor and esc installed .

Hopefully by the time I get back, the wind will have died down. Even slightly. Been atrocious for the last week.

-Hawk

kyleservicetech 05-22-2014 02:34 AM

Quote:

Originally Posted by dahawk (Post 948819)
Here is the first test of the 120 size all metal HK retracts. Pretty sturdy. 5mm pin to oleo: http://youtu.be/NZfri_eOALA

Now these are $65.00 for the set. Another ~ $20 for the main 130mm long oleos and the offset 108mm long nose oleo strut. Yeah, not in the same league as the Robarts but I think they'll serve the purpose: Taxi to runway, take off roll, rotate, gear up , fly around, gear down, land.

If they hold up, I'll put a set in my EMB-312 Tucano and Deuces Wild.

I do admire those guys with the bottomless pit for a bank account who fly wet turbines. A blast to watch. I'll never get there. Still trying to master the 70mm foam versions. I could add up my entire squadron of 20 plus planes, sell them all and would still be a few thousand short. LOL

Have to travel Friday through next Thursday so I was hoping to get some of the conversion done before I left. Hopefully tomorrow, I'll get the motor and esc installed .

Hopefully by the time I get back, the wind will have died down. Even slightly. Been atrocious for the last week.

-Hawk

Yup
Your model doesn't land with 40 pound weight, and land at 50 MPH!

As for finances, that club member is retired, so, he's also got to watch the $$$$.

CHELLIE 05-22-2014 02:55 AM

Quote:

Originally Posted by dahawk (Post 948788)
I'm in the process of converting a gas Great Planes Piper Cherokee to electric incorporating a set of all metal HK servoless retracts .This will make it a Piper Arrow.

I actually bought the plane used from a buddy and he had already added air retracts. What a project. All I need to do is switch them out. Sounds easier task than it is.

I'm removing the air retracts and the first thing I noticed on the HK steerable nose gear is that besides the normal arm that the servo pushrod/ clevise rides up and down on while the gear lowers and raises, there's a small compression spring attached with a screw to the base.

http://imageshack.com/a/img838/1129/730yt.jpg

Where does the other end of the spring attach to ? What does it do? Is it a centering spring?

Thanks ,

Hawk

Hi Hawk :ws: The spring looks like a retainer to hold the bottom piece of the landing gear to the shaft and retract Assy. Bottom of the Pic, Take Care, Chellie

http://www.hobbyking.com/hobbyking/s...alog/43300.jpg

dahawk 06-19-2014 02:58 PM

The Piper Cherokee conversion is now complete and ready for maiden:

http://imageshack.com/a/img850/6883/db9j.jpg


It's now a Piper Arrow with retracts. The biggest PITA was the retracts. The HK 120's simply failed. Truly a POS. Went to PW-RC and bought a replacement set. Phillip shipped from Hong Kong and they arrived registered mail in 1.5 weeks. Pretty good service I'd say. They're not all metal but have metal trunnions and a 5mm dia pin hole. Using the 130mm long HK oleo struts for the mains.

Will run on 5S with a 12x8 prop. Wish I had enough clearance for a 13 x6 but I don't.

Not crazy about the motor mount or the Exceed 660KV motor. It's a universal setup from GP. Had to add a locking collar to the shaft to get clearance for the cowl and spinner back plate. Holes didn't line up on the motor to mount interface exactly.

The only other thing I did was added a nylon wing nut for the canopy. Removes fairly quickly now.

-Hawk


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