Onex landing gear issues

[wolfpack3]

I currently have about 20 flying hours on my Onex. I have had problems with the brakes since day one. Go-kart brakes don't work on an airplane! Went to the upgrade drums with no improvement and then I ordered the hydraulic brake system that Sonex puts out but when the kit came the invoice said that the pistons and pucks were back ordered! Back it went.
Finally I decided to go to Matco hydraulic brakes and wheels. The problem is that the Sonex gear legs don't except any other brand of brakes but the ones they use due to their own hole pattern. Why they didn't design a Cessna hole pattern that would except a number of different products is beyond me. It would have been better to leave the end blank!
After much consideration I have decided to purchase the Okeefe Aero gear legs after looking at both Grove and Okeefe. The first thing I noticed is the difference in thickness of the material they both used. Okeefe uses 2024-T351 5/8" thick and Grove uses 7075-T6 which is 3/4" thick!
This is quite a difference from the 1/2" material Sonex uses and I am suspect of the strength of such a thin material especially if it is 6061(just guessing about that) which is NOT a particularly good choice to be used for spring gear IMHO. I know of another Onex driver that had almost completely collapsed his gear on his first landing however, Sonex did send him a replacement. Being just barely strong enough just doesn't sit well with me. It would also be my preference to do my own drilling of the hole pattern at the axle so I could decide what I wanted.
This is a valid safety issue that needs to be addressed by Sonex but I don't see anybody else talking about it here. Maybe the time has come.

[MichaelFarley56]

So, just so I understand, you have 20 hours on your Onex and have had no issues with the strength of the gear, yet you say it's not strong enough? I haven't heard of anyone else having any issues either other than your story of your friend. Just how good (or bad) was that landing?

Having been a CFI for a number of years, I can attest that a Cessna 152 has incredibly strong gear yet people have still managed to bend them up (somehow). I'm fairly confident that regardless of how strong gear legs are, if you slam down hard enough they will bend! It doesn't matter how thick the metal is.

Sonex drills out the gear legs to make things easier and quicker to install for builders. It's part of the "matched hole" technology that most builders demand in today's market. And this is just my opinion, but if your friend bent up his gear on landing and Sonex sent him a free replacement set, I call that incredible customer service!

As for the brakes, can you tell us what's so bad about them? I had the machined drum, mechanical brakes for a while and despite some humorous squeaking when coming to a stop, they worked fine. There's a lot of builders using that setup with no issue, so some additional info may help.


Just my two cents of course!

[Mike53]

Sorry but I'm just not buying it.Everything about the Onex is overkill.The spar could support an elephant .I don't believe for a moment that the Monnets would suddenly decide to use an inadequate or 'barely strong enough 'landing gear .Any landing gear wether on an experimental or certified airplane will collapse if you push it way beyond its designed limit and no company would be immune from such a catastrophe,if you try hard enough.
When I look at my Onex landing gear I don't get the feeling I need thicker and therefore heavier gear.Granted I'm no engineer but my Onex gear looks more than adequate.
Happy landings.
Mike

[wolfpack3]

My brakes have never worked properly. When the shoes contact the drum they do not nor have they ever made straight contact with the drum causing the brake to lock up. They have been disassembled numerous times to remedy the problem but never have been fixed. These brakes are manufactured for the go-kart industry to stop a vehicle that weighs 150 lbs or so...not an airplane weighing 650 lbs+.
As far as the ease of construction on the gear leg, is it any harder to drill 8 more holes in the gear leg at the axle when you are already drilling 10 holes to fit it to the fuselage?
The strength of the spar has nothing to do with the strength of the gear leg. Yes, there are some parts that are very sturdy I agree. I also agree that if you land hard enough in anything, the gear will collapse. As far as my friends issue, Sonex did admit that the gear he received was bad and they had had some issues with them. Since I have been flying my Onex the wheels are no longer sitting vertical as they were at first and I have yet to make a bad landing but standby that may change on the next flight lol. It's not "if" but "when" right? I find it interesting that none of the other manufacturers producing a similar product that is made from 1/2" thick aluminum in any alloy. Fly what you're comfortable with...that's why they call it experimental.

[onex28]

Wolfpack3, did you go with the Okeefe hydraulic brakes and if so what is your opinion of their stopping ability? I’ve worked my way from band to machined and now Sonex hydraulic. I don’t know how long it takes to break in brakes but I want better performance after 6 landings.

David

[WesRagle]

Hi David,

I don't think Todd has been on the list in a long time. It's been a couple of years since he's posted. So, I hope he doesn't mind if I answer for him.

I asked him that same question back in March of '18. His reply:

I put Matco wheels and brakes on mine and I can change the caster and camber with washers to suit my needs.

As a side note, my Sonex hydraulic brakes have gotten a lot better with use. If you intend to ditch them anyway, why not abuse them and see if they improve. Make sure you have the proper washers installed and aren't getting grease on the pads.

Good Luck,

Wes

[onex28]

Thanks Wes, I’ll recheck everything, give them heavy use and hope they improve.

David

[achesos]

Brakes can / do improve with use (until worn out of course).
Search the internet for "bedding brake rotors" for reference. Essentially, the rotors become less slippery if properly heated and pad material transfers to the rotor... but this would be hard (if not impossible) to perform on an airplane, but is quite common for racing applications. The 'science' here simply explains why performance may improve over time or the # of landings if you're interested.

[flyingbear]

I put Okeefe landing gear on my ONEX....two inches longer than standard. Also put Okeefe hydraulic brakes. They are AWESOME and I can brake more with my little finger now than I could pulling with all my strength on the mechanical brakes (Which are in the trash) I will have to modify my wheels pants - widen them- but well worth it.
Glen Bradley
ONEX 0131 189 hours

[flyingbear]

PS---- I used the Sonex master cylinder and moved my flap handle outboard. Works great. Wheel cyls were Okeefe.