I grabbed some 4mm plywood (just ordinary pine), bought some wire and wheels and had at it. The result is shown below.
The first version of the wheels mounted on the wing. They are held on by 2 cable ties, one that goes through the motor mount at the back, and the one that holds the battery in as well. An issue here is that takeoff takes a long run because the wing does not have enough incidence. Basically it gets off when the nosewheel hits a bump and bounces up! The bolts holding the plywood away from the surface at the back are the problem, since if that area was flat and the plank could be held flat against the trailing section of the wing it would be at about the correct angle.
Despite that problem, I had a few good flights with it like this. In the lower image you can barely see that there is red tape on the plank, which is covering some big holes I drilled because the wheel assembly adds significant weight.
To solve the takeoff run issue I cut some balsa blocks to put between the plank and the wing. The first was 10mm and worked quite well until it fell out during a flight. I then put in a 12mm block which worked even better but increased the drag during flight.
The ultimate solution to the angle issue is a new nosewheel that is longer. As I added angle between the plank and wing I noticed it needed more and more up trim, and flew a bit more sluggish. The sharp will notice that this nosewheel is made from 3.2mm wire like the back legs, whereas the first nosewheel was 2.4mm wire. I found that even a reasonably slick landing would bend the 2.4mm wire. The new one has a few turns for spring but it is heavier, so I cut the plank shorter to keep the CG in the same position. Some would say that if I'd left the plank long I could then remove some noseweight to rebalance, thus reducing AUW. I chose not to do that because I want the wing to be balanced without the wheels mounted so that I can choose to fly without the wheels. I believe a better solution to the excess weight is to move the motor further forward and use a long shaft and extra bearing to support the prop at the back.
As at 11/25/2009 this modified nosewheel is unflown so hopefully I'll remember to come back and report on it. We're having a season of such high wind at the moment such that no-one flew last weekend, and it is still blowing.
I am considering some options for the future, one being to mount an extra servo that can ditch the wheels after takeoff since it does fly rather nicely without the wheels. Another is to make some sort of elastic powered launcher, something like a spear gun that can be fired one handed.
At least now I can fly it with a good assurance of not breaking the prop, so now I can try some different props that I have, that cannot use the prop saver.
|talk to me|
If we ask anything according to His will, He heareth us
1 John 5:14
|Many people cannot afford their own Bible, please help them now|