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Suggestion on fixed landing gear mod

Old 04-16-2016, 06:03 AM
  #1  
FoxProGT
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Default Suggestion on fixed landing gear mod

Sup peeps...

Bought my second plane a few months ago and waited for nicer summer weather to fly it. Today was the day and all went well until the final landing.

I don't know if i came in to hot or hit a patch of crab grass but i ripped off the landing gear and the plane flipped on its top.

The damage is fixable but i kinda don't like the way the gear screws onto this small black plate that is glued onto the foam. I feel that is not adequate contact area for good gear support.

That black plate was pulled off during this crash landing too so screws being pulled out wasn't the case.
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Old 04-16-2016, 06:20 AM
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fhhuber
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Glue the pieces of foam back... and insert toothpicks 90 deg to the repair joint
this will reinforce the repair and spread load over a larger area.
Probably 2 toothpicks each, front and rear.

That will make it require more force to break again.

Note: if it rips out again it might rip out a much larger area.

While split bamboo from barbecue skewers would be less likely to break than the toothpicks, you kind of hope the toothpicks break before the larger area rips out of the belly.
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Old 04-16-2016, 06:47 AM
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hmmm barbecue skewers sound good. I was considering using break away screws too.
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Old 04-16-2016, 06:49 AM
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I tried nylon screws retaining the landing gear... you have to make a perfect landing or they shear.
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Old 04-16-2016, 07:44 AM
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solentlife
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I agree that many models have weak gear mounts and they break out too easily. But too often I feel people tend to over-strengthen mounts and then find serious damage when they rip gear out next time. I'm a great believed in keeping damage to the immediate area and as limited as possible.

Not trying to upset anyone - but I know this from my own landings - most times gear rip-outs are down to pilot having a hard landing or on unsuitable ground.

We cannot have light models and string gear mountings. A compromise has to be accepted.

My Yak 55 and Katana rip out often. But they still glue back in original position without too much damage around. The Katana is particularly bad so I cut a ply plate to span the slot completely instead of the two piece affair of original. So rest of fuselage is unchanged, but gear now has a spread load plate ... later I fitted a one piece landing gear instead of the two separate legs.

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Old 04-16-2016, 10:40 AM
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Yeah i think i had a mix of both hard landing and bad grass. My sport cub spoiled me with its giant wheels and bendy wire gear. Im liking the break away screw idea to keep me on my toes on landings. I just feel there could be a way to mod this for alittle more strength.
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Old 04-16-2016, 10:48 AM
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some more strength... some toothpicks.

maybe half length.

Bamboo is asking for a big rip out.
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Old 04-16-2016, 01:02 PM
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May want to consider ditching the wheel pants. Larger wheels sure can help on grass.
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Old 04-16-2016, 08:09 PM
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defiantly taking the wheel pants off for awhile. maybe get some softer wheels.

Thanks for the input peeps.
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Old 04-16-2016, 10:48 PM
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Just remember if you were landing a full size Cub on the equivalent size of grass to your plane you would be using huge 'Alaska' tyres for sure.
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Old 04-17-2016, 04:51 AM
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Unless you have the broken chunk intact, I would consider squaring up the existing hole, filling it with EPP foam and shaping it to the fuselage. The replacement chunk could consist of alternating layers of foam and thin ply, with the final layer being 1/8" ply for attachment of the gear legs.
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Old 04-17-2016, 03:50 PM
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The problem is if you beef up the area the model will just break at the next weakest point so you are always chasing repairs. Take an old electric motor apart and remove the magnets. Glue 4 magnets to the fuselage of the model flush with the foam. Glue 4 magnets to the undercarriage in corresponding position to fuselage magnets making sure you get polarity right. This will hold the gear on pretty solidly and in the event of a hard landing becomes the weak spot and detaches. All you do then is reattach.
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Old 04-17-2016, 04:03 PM
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Originally Posted by squidger View Post
The problem is if you beef up the area the model will just break at the next weakest point so you are always chasing repairs. Take an old electric motor apart and remove the magnets. Glue 4 magnets to the fuselage of the model flush with the foam. Glue 4 magnets to the undercarriage in corresponding position to fuselage magnets making sure you get polarity right. This will hold the gear on pretty solidly and in the event of a hard landing becomes the weak spot and detaches. All you do then is reattach.

How to have the wheels fall off while taxiing out on smooth pavement...
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Old 04-17-2016, 04:48 PM
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Originally Posted by fhhuber View Post
How to have the wheels fall off while taxiing out on smooth pavement...
I have to agree as well. I cannot see 4 magnets holding U/C ..... given that screws and plates rip out ... especially Motor Magnets ... which are not the most powerful.

I have larger magnets that I bought specially for canopies etc. and I would not trust those either on U/C.

I'm even reluctant to trust cockpit / canopy magnets !

Nigel
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Old 04-17-2016, 05:21 PM
  #15  
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I add other means to secure canopies because I was constantly blowing off any canopies just retained by magnets.

Often all it took was an outside loop of moderate diameter. Not anywhere near use of full throw.
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Old 04-17-2016, 10:27 PM
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I think the ugly truth is that every model needs a certain degree of strength to absorb hard landings without constantly having to repair the structure. As it is, most models probably absorb more relative punishment than any 1:1 plane. If you continue to wipe out the gear and/or it's mount you have a problem:

* Your landing skills need work
* You are flying off a surface inappropriate to that particular model
* Your gear/wheels/tires are in need of a redesign or modification
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Old 04-17-2016, 11:28 PM
  #17  
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I used motor magnets to hold a canopy on once and removed them because they were too strong. Getting the canopy off became real hard work. If you put 2 motor magnets together you will find it hard to pull them apart.They snap together with quite a force. You have to slide them away from each other. The gear certainly would not fall off while taxying on smooth tarmac but would if it hit rough ground on landing.
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Old 04-17-2016, 11:46 PM
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Had a hatch magnet fail me on a Mountain Models Firestorm yesterday. Canopy cracked and took out a hunk of the top of the wing about 200' up. I never have been a huge fan of magnets but now even less. Hatch magnets can be "OK" when the hatch is trapped and the only way the magnets can be separated is pulling them directly apart. Any amount of side movement or slide and you can be sure it will separate.
These magnets were located on the rear of the hatch where it slopes up to the turtle deck. Replacements will be located perpendicular to the hatch and pins will be added to insure the hatch only moves directly upwards.
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Old 04-18-2016, 05:20 AM
  #19  
FoxProGT
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Ok guys did some repairs this weekend. I didnt add anything special so its a stock glued plate to hull mounting BUT i will add a landing gear with suspension. The Wacos wheels look ridiculously small without the wheel pants so ill slap on the sport cubs bush wheels. Hopfuly that will be a winning combo for sturdier grass and bump handling. Check it out......
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Old 04-18-2016, 06:57 AM
  #20  
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Caution with that... you are moving the wheels either forward or back. Forward can make it hard to steer, back can make it hard to keep the nose out of the dirt.
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Old 04-18-2016, 10:01 PM
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Looks like most of that action would be up and down, not longitudinal. You can get the same effect without the complication just by using soft tires. My Experimental homebuilt's only suspension is a couple of fat tires with 8-10 lbs of air in them. They take quite a hit.
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Old 04-18-2016, 10:19 PM
  #22  
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Not saying his wheel action due to the spring is anything other than mostly up and down...

The trailing link moved the axle location ( assuming its trailing) back by appx the radius of the tire.

Taildraggers are really sensitive to that.
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Old 04-18-2016, 11:36 PM
  #23  
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Oh, absolutely. And it doesn't take much. I was assuming the OP was showing an example of what he was planning, not his current gear
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Old 04-21-2016, 08:47 AM
  #24  
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That pic IS the gear im using. The repair is done and ill take it out this weekend for a test. I do still like wheel pants better but i don't mind this look for better grass landings. The wheels on it are from the sport cub but i might pick up a set of air filled tires for extra cush.

Might be tuff to see but the stock gear went straight down from the fus but these are swept forward with the swinging arm facing back so that the wheels are close to the stock location. Ill find out how it handles this weekend.
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Old 04-21-2016, 08:52 AM
  #25  
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If the axles come out at the same place as original, it should be fine (except possible toe-in/out issues)
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