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Aug 18, 2019, 07:58 AM
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AJ Proteus Gear Strut Modification

Follow-up from Post 68 & 71

Based on thread comments regarding the ground handling behavior of the AJ Proteus (heavy tendency to flip over its nose on grass runway while taxiing, on take-off and landing roll due to main wheel axis been too far back), I have come-up with a mod to relocate the gear more forward in order to change the wheel's axis. Refer to picture # 5055

Here’s the steps involved:

1. I purchased a Pilot RC CF landing gear for the 30% 87’’ YAK 54 / 28% 88’’ M55 available from Chief Aircraft (USA) as item PRC LAND YK-30 or AMR Hobby (Canada) as item YAK54M55-88-LG (SKU 3180).
2. The gear has been cut in two half using a Dremel cutting disk. Refer to picture #2650
3. The axle holes being too large for the Proteus axles and wheels, I decided to cut the gear bottom parts and re-drilled new holes to accommodate the original Proteus axles. Refer to picture #3812
4. The bottom part of the gear had to be sanded approximately 2 to 3 mm to accommodate the wheel pants width where the axle attached to the gear. Refer to picture # 3812 & 2162
5. I then opened up the bottom area of the forward fuselage to have access to the landing gear attachment plate. This way, it was much easier to align the CF legs into the pre-set holes for proper fit rather than create a template. I drilled a pilot hole thru the blind nut to reach the CF legs. Refer to picture # 8273 & 2756
6. I reinforced the front opening by adding balsa “cross” support which has improved the surfaces for the Oracover covering. Refer to picture # 2756

The new CF gear legs installation moves the wheel axis approximately 6cm (2¼ to 2½ inches) more forward. CG was check at recommended 166mm from top wing L.E. A Pulse 2550 mah Rx lipo battery was installed just forward of the rear upper wing screwing plate. Refer to picture #1330.


Ground handling tests have been completed on August 17 and the results are satisfactory. The model has NO tendency to flip over its nose from low to high-speed taxi and without UP elevator input (note: as we all know, it does remain a good habit on tail wheel model to use up elevator while taxing).The mod does improved the behavior of the Proteus on moderate lentgh grass runways.

Unfortunately, the weather did not collaborate and the maiden had to be rescheduled to another day (maybe today). More to come…!
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Sep 21, 2019, 09:08 AM
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Last edited by kdunlap; Sep 22, 2019 at 11:15 PM.
Sep 22, 2019, 10:55 PM
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Last edited by kdunlap; Sep 22, 2019 at 11:15 PM.
Sep 29, 2019, 04:18 PM
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Radical Surgery on The Proteus

So, I really like this airplane and the first few flights were very nice. However, take off and landing were a nightmare because of the effect of the sweep on the landing gear when flown off grass. Same problem everyone else is having. Read the thread and did some research and settled on these from Mike at F3A. -Just a word on this gear... these are a work of art at an incredible price. Thanks Mike!! Pre-molded pilot holes, centering lines. Everything to make a smooth install possible. Can't say enough about these. They are for the Allure and Alchemy but fit the the Proteus with only a mod to where the gear bolts go. No big deal.

Hence, I digress. I fly off a well groomed field and we hold the length just a bit more than 1". The field reminds me of something between a fairway and putting green. The Proteus was clearly designed for concrete and not for grass. Period, end of story. The Acuity has the same problem with gear that sweep way way too far back for grass. At least on the Acuity 25 degrees, yes 25 degrees up elevator on take off fixes this problem. Hence I digress.

Dear AJ-Aircraft: Please remember not all your customers fly off concrete. How's about offering gear on both the Proteus and Acuity with less sweep.

You can see from the pictures I needed to remove the fwd section of the belly sheeting to get to the gear nuts. I replaced these with 6-32 blind nuts and stainless steel screws.. Why screws? Because you need at tool with at least a 9" reach to get to the fasteners from inside the fuselage. Far more convenient than a hex driver and far cheeper than a hex driver with a 9" reach. I am incredibly pleased with this swap out. The original socket cap screws were way too soft and I stripped a head. Voila 2 hrs unplanned gymnastics.

I laminated a sheet of carbon fiber to the plywood gear plate and frankly if I rip out this gear the plane will likely rip into two pieces.

The new gear has a sweep of 1.5" and the AJ was swept to about 3.75" I am hoping the reduced sweep will help. Couldn't find gear with zero sweep.

In summary, it has cost me $150 to swap out parts that come with the kit that caused problems with the build or flying it. I love the guys at AJ and have every pattern plane they have made, even going back to the 48 and 62 in Osiris from 3DHS, a 2M Osiris prototype, an Acuity and a Proteus. Proved my loyalty to the brand. Just hoping they can make a V2 that fixes these issues. I will be a customer again.
Oct 09, 2019, 06:31 AM
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Has anyone, who owns a Proteus or has access to one, actually flown either the AMA Advanced or Masters Pattern? If so, could they please provide some in-depth, first hand knowledge and/or experience with this biplane.
Oct 10, 2019, 08:17 PM
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So here's my flight report from today with the new gear. In general, ground handling greatly improved. I was able to take off without 25 degrees up elevator as a condition setting. Took off with 10-12 degrees very easily. However, on landing at the end of the landing roll, the plane would nose over even with full up elevator due to the drag cause by grass of 1.75". Moral of the story is this airplane can not take any sweep in the gear at all. I would recommend what Rtrembly did in post #76.

On the other hand every flight on this airplane makes me appreciate this model even more. It flies very cleanly and precisely and is a joy to fly. On my 6S setup I easily got 6:15 of flight time doing aggressive vertical aerobatics. If you can fly advanced or masters in 6:15 this setup will work for you. Did a few snaps and they were very clean. On par with my Acuity. This airplane will definitely handle advanced on 6s. For Masters you may want to go 8S per the recommendation. This airplane will handle whatever you can throw at it. Especially if it needs rudder. -Ken

I forgot to add that I am going to change out the tires from 2" to 2.75" or 3.0", depending what fits. This might stop the nose overs on landing roll out.
Last edited by kdunlap; Oct 10, 2019 at 10:40 PM.
Oct 11, 2019, 07:03 PM
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So I swapped out the stock 2" wheels for 3" wheels and this solved about 90% of my problems. I need to land and keep the motor running to blow air over the tail to keep the tail down on rollout. Lessons: no sweep gear and bigger tires. That said this airplane is just a joy to fly. Stupid powerful rudder.
Oct 11, 2019, 08:05 PM
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Originally Posted by kdunlap
So I swapped out the stock 2" wheels for 3" wheels and this solved about 90% of my problems. I need to land and keep the motor running to blow air over the tail to keep the tail down on rollout. Lessons: no sweep gear and bigger tires. That said this airplane is just a joy to fly. Stupid powerful rudder.
Thanks for posting so much great information, i have one I have put off putting together because i normally fly at a grass field,
Oct 11, 2019, 08:12 PM
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Andy put it together and fly it. Make the changes suggested here and you'll have a big smile.

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