Question: I have a set of the VMAR Oleo Struts for my VMAR Jet (Prop) ARF. Do you have any tips re installing them?
Answer: Here is a procedure that will work with the VMAR Jet (Prop) ARF's and most other models assuming that the factory standard gear is made from 5/32 to 3/16" wire.
It's important to understand the basic approach first:
Examine the oleo struts and you will find a channel running down the center of each strut from the non-wheeled end. This channel has two set screws entering it from the side of the strut. The oleos are installed by cutting the factory wire landing gear to the correct length and sliding the oleos over the factory wire landing gear "stubs" after you have the length of the wire cut down to fit. The oleos are then locked on to the wire by the set screws.
Now for some specifics:
- Test that the factory gear wire is of a diameter that fits into the channel running vertically down the center of each oleo strut. If the wire is too large in diameter, you will have to make (talk to a friend with a wire bender) another set of gear from wire that will fit into the oleo strut OR you can try to adapt by using the extra wire studs provided with your oleo strut set. For the purposes of this procedure, we are going to assume that the factory wire set is of a diameter that will fit into the strut channel or that you have made up a new wire set that does.
- Set up your model with the factory fixed gear set and factory wheels first.
- Using a tape measure, measure the following distances:
- Height of the prop tip from the ground when the prop is closest to the ground
- Height of the fuselage above the ground at the nose gear leg position
- Height of the fuselage or wing above the ground at the main gear leg position
- Height above the ground of a reference point at the tail end of the model.
- Label each of your oleo struts, "Nose", "Main-Left" and "Main-Right" appropriately. Use low tack masking tape and apply the labels directly to the struts.
- Back out the set screws from the "legs" of each oleo strut. Don't remove the screws, just back them out so that the internal channel is clear.
- Using a piece of wire or rod as a probe, measure the depth of the channel from the "bottom" closed end of the channel to the top exit end of the channel for each oleo strut. Write this number on the label attached to each strut and on a sheet of paper with the measurements you made earlier.
- Now calculate the amount that you will cut off the bottom of your factory wire for each leg so that the distances you measured earlier can be maintained with the oleo struts installed. If you want to increase the ground clearance somewhat that's fine, just make sure that all four distances increase by the same amount. In fact, we suggest planning on 1/2" longer legs to start to give yourself some room to adjust things later. The idea here is to make sure that the angle of incidence on the ground is the same after you install the oleo struts as it was before. If the vertical distances are the same as before or all longer by the same amount, then the factory angle of incidence on the ground will also be the same.
- After you have measured everything twice (remember the old carpenters maxim... think three times, measure twice, cut once!) mark and cut the factory wire gear legs. Again we suggest about 1/2" too long to start. You can always cut wire a bit shorter but once it's cut, there's no way to grow it longer!
- After cutting off the excess wire from each factory gear leg, slide the oleo struts into place over each wire stub. Align the wheels to so that the nose is straight ahead and the mains are 1-2 degrees "toed in" (this helps ground handling). Now measure the same vertical distances that you did earlier. Make sure that they are the same as before OR if one is higher by 1/2" that all of them are higher by the same 1/2".
- Make any final cuts to maintain the angle of incidence on the ground
- Remove the masking tape labels from each strut and you are done.
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