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Author Topic: nose gear survival  (Read 431 times)
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kwikfly
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« on: May 11, 2017, 02:25:40 PM »

Good evening all.
I haven't found any mention of nosegears anywhere, thus I started a new topic.
I don't know why myself, but I don't like taildraggers; I always build tricycle planes. And yet, I have a problems with nosegears. It was ok with these 60" trainers, that have a coil in the noseleg. Never broke one. At worst, sometimes the noseleg would bend aft on landing, making the prop dig into the ground and your clubmates laugh at you. A bit different with larger scale models; with these noselegs with shockabsorbers and... that are always angled to the front.
Last year I had a scratch built Marchetti SF260 (2m/6ft span, 7kg/16lbs) that had Robart retracts. Flew nicely, but after about ten flights I made a less than perfect landing. The nosegear collapsed, it survived but it destroyed the firewall, tank compartiment, and my desire to repair.
Now I have this Monsun, a Graupner ARF kit (not my thing, these ARF's but it's a beauty), a 2.20m/7ft span plane with a fixed tricycle gear. The nosegear has a shockabsorber and is supplied with the kit. I have logged a dozen flights with it but this is the f**** 3rd time I have a noseleg bent aft. Any landing that is not perfect means hours work to remove the prop, silencer and cowling to remove the gear, remove the 6mm steel rod inside the shockabsorber, make a new one and reinstall the lot.
This is not funny anymore. I don't want to dump this model after only a few flights, not again! I would like to enjoy flying again, including the landings! And yes... I still want to do it with trikes.
Anybody any ideas? What can I do (apart from making better landings. Hahaha.), has anybody had the same issue and what did you do about it? Is there any way of absorbing the energy of the nosegear hitting a bump on the runway? Thanks for the help!
Jo
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Jack Plane
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« Reply #1 on: May 11, 2017, 04:22:16 PM »

Switch to a flying site with a smooth hard runway?

Aside from unhelpful suggestions like the one above, the common theme in your two examples is that, as both planes are large and fairly heavy, there's a huge amount of forward momentum:  if the nosewheel hits an obstruction and the undercarriage cannot in itself absorb or in some way deflect the energy, then this is going to be transmitted directly and cause shock to the nose area of the fuselage.

The answer is to make the external part of the forward undercarriage either the weak point in itself, so that on a very hard knock it detaches altogether (with eventual but limited slow-speed scuffing of the nose and a broken prop), or create more flex in its external part.

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Bill G
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« Reply #2 on: May 11, 2017, 04:26:53 PM »

It does seem there are generally 2 options:  Destroy the firewall mounting area, or have a strut that is thin enough that it bends, even with a spring loop.  I never tried it, but I image using a good spring steel wire, but of a relatively thing gauge would work for the spring loop, being able to deflect easily while still keeping it's memory.  It would seem that the strut would need to be stronger, and slipped over the spring loop with something like a set screw, as whatever gauge would work well for the spring loop would be too weak for the strut, and would still bend along the strut portion.
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