I have modified one of the earlier Durafly P-40N prototypes I had gotten from Stuart Warne at Hobby King to accept these Landing gear units. They offer the same 100deg forward rotation with the 90 twist to stow flat in the wing like the P-40 and F4U.

It is quite a bit of work as these are far from being drop in replacements for the stock solid strut units. But if you are interested in repeating this, keep reading.

You will need:
a dremel tool and a 1/8" router bit.
a disk or belt sander
3/16" (5mm) wood dowels
#2 sheet metal screws.

Let's get started.

First thing is to remove some plastic/foam from the bottom of the LG mount. You need to remove about 3/16" deep from the existing pocket. I used my dremel with a 1/8 router bit to do this. Unfortunately, you must also remove the tube spar that runs though the pocket. Not to worry though, the new LG unit, bolted to the model will provide some added strength.

This is what it will look like when done

Now we have to work on the new retracts a bit. The width needs to be reduced to fit in the model pockets, a new bolt hole needs to be drilled and the fwd holes need to be elongated inboard to match up with the old screw locations.

after I taped up the unit (to avoid getting chips and alum dust in the mechanism) I sanded the mounting flange to 32mm wide to match the old unit.

Nice thing about these new units is that they have two strut lengths built in. Mine came with the "strut-stop" screw in the short length hole. Just remove it and reinsert into the other hole for a length just perfect for the P-40N!

The axle hole will need to be enlarge to 3mm so you can use these pins for the axle.

Now put the unit in the prepared mount and elongate the fwd mounted holes as required to use the old holes in the plastic mount.

the outboard aft hole in the new unit will be used, but there is not much plastic for the screw to grab so we are going to insert a 3/16" hardwood dowel vertically in the wing for this hole and new inboard aft hole we will drill int he mount.

The new unit installed will have the same rake as the stock unit and should provide some shock absorption. It could be a little while before I get a chance to fly this mod. I will report back when that is done.

I have no doubt this will be a great improvement over the old units on my less than perfect lumpy flying field.

Here is a quick movie to show them in action.

Note that the current (for both units) barely gets to .75amp on the bench. It will be a bit higher with air load, but I see no reason why the stock BEC in the ESC cannot handle the load.

As this was one of the early prototypes, DF had not sorted out the LG doors on this one. I will have to try and get a set of the new ones with the springs and see if I can make them work. If not I will just model them in the closed condition with a slot to allow the leg to pass thru.

I still have to cut the axles down too, but I am all out of cut-off wheels for my dremel! Drat!

DF P 40 LG sequence (0 min 40 sec)

Nice upgrade Tom, thanks for sharing.

How does she handle the extra weight? Just fine I should think.

S.

Thanks S.

It will be a while before I get a chance to fly this wing.... gotten frightfully cold now here on a not-so-tropical-island off the coast of the US!

Obviously the gear weigh a bit more being all metal, but yes I don't see any reason why it will adversely affect the flying qualities. Landing speed may go up a MPH or 2. CG can be adjusted with the battery.

Tom

This mod adds 19 grams per gear with a total of 38 grams or 1.33 ounces. I think this model can handle that small a weight gain. Heck, some guys are putting heavier batteries in it that weigh more!

Thanks for the instructions. I am very frustrated with the retracts on my P-40. I'm on my second set, and those already broke this weekend. Had the smoothest landing, full flaps, no bounce and very gentle approach, and this set also broke. I even had an observer comment on how weird it was since it was a perfect landing. They just collapsed upon touch down.

These look to be some very nice retracts. Stuart, would you ever consider selling a "hop-up" retract set for the P-40 that would include these retracts and a modified retract housing made for them? That way the only real work to installing them would probably be shaving a little foam from the existing pocket.

Thanks!

Fergy

Hey Tom,
What is the size difference between the stock Durafly wheels and the wheels that come with these oleo retracts?

Thanks!

Fergy

I'll check when I get home, but they are tiny.... maybe no bigger than 2". The wheel shown in pot #5 are what come with the oleos/retracts