Props4ever

I'm seeking info on the strut length and wheel size that would look right and very very close to scale for Nosen P-51 and Ziroli P51D Mustangs.

It looks and feel as length of my Nosen Mustang is short then it should be and wheels on it are Dubro "Skylite" 4.5 foam types.

I want to have scale length of my struts and wheels, thanks for ur help in advance...

saramos

One of the issues you need to take into consideration is that when the full size P-51 is sitting on the ground, the struts are compressed. Once airborn, they extend to their full length. Model struts do not compress in the same manor when a model is on the ground. As a result, if you make the length of the struts such that the model sits properly, when the model retracts the gears, the strut will be too short to retract the wheel in the scale position. Likewise, if you make the struts the proper lenght to bring the wheel into the scale gear bay, when sitting on the ground the struts will be too long and the plane will sit with the nose higher than it should be. Most often, you will need to make the best choice based on your own thoughts as to which is more important, proper stance, or scale location of gear and wheel well, or perhaps some compromise of the two.

I started a P-51 project (TopFlite) a few years ago where I wanted to try and address this problem. I was experimenting by modifying the springs inside a Robart strut. I cut the main spring shorter, then added a softer and longer spring that would nest inside the original spring. The intent is for the softer spring to be able to compress under the weight of the model, but extend the strut to full length once off the ground. I set the project on the back burner, and cannot report as to the effect it will have on the function of the struts under real landings. It may turn out that it works, or it could be that it will mean that the gear rails may fail easier under a rough landing. Another possibility is that instead of cutting the original spring, that it would need to be replaced with a slightly stiffer short spring, but calculating the best solution is beyond my means. When I get back to my P-51 project, I will have to experiment to determine the best way to achieve the result, if at all.

Another approach would be to use some sort of mechanism to compress the gear some as it is extended. Again, it may cause the landing stresses to be transfered more into the structure of the wing.

Scott

Props4ever

Scott,

My Nosen Mustang has fixed gears, so for me compression of the oleos are not an issue at all.
I like to make newer wire main gears with proper length and wheels on them. With 24x10 prop, with model at level, ground clearance of the prop is only 2"!!....
Take a look at these pics to get an idea n later in evening i'll post present length of wire struts.

Sam

rcphotog

IF all you want is to have the model sit at a scale angle while on the ground then here ya go.

The deck angle is the same for the P-51D as well.

I think you're model is pretty close to a scale stance already.
Ken.

Lnewqban

Two more pictures and one drawing as references:

Props4ever

Thanks Ken, ill check the angle of my model and go from there.

My 2nd part of the question was about size of the wheels, I have seen guys with 1/5th scale Mustangs using 5" wheels on there models, Nosen Mustangs are shy of true 1/4 scale, so would 5.5" or 6" dia wheels will be right for them?



Sam

saramos

I would think that at nearly 1/4 scale, the wheel should be closer to 7" - 8". I don't have the info handy, but when planning out my 1/7 scale P-51, I had come up with the 4" being closest to scale. At 7", that would corrispond to a 28" diameter wheel. I would think that 28" would be about the minimum size of a warbird main wheel. I am currently working on a Corsair. It's main wheels were 32", which would be 8" at 1/4 scale.

Scott

Lnewqban

If not sure, decide in favor of the bigger wheel.

The obstacles that that wheel will have to overcome are seldom scaled down.

saramos

A quick check of a Tamaya 1/48 kit I have came up with a value of 28" for the main wheel.

Props4ever

Just did quick scale calculation, scale wheel size is 28", so i divided it by 4.5 since this model is shy of being 1/4 scale, wheel size comes out to be 6.2" for main wheels for my Nosen Mustang.

Does this number feels good to you guys as i'm getting 5.5" inflatable wheels for my model.

saramos

I looked through the factory drawings I have and found the specs listed in drawing 99-3300-1. The true full scale diameter is 27". Looks like 6" is very close to dead on for your Nosen. A true 1/4 scale would have been 6 3/4".

Scott

saramos

Of course, you will need to take into consideration what will comfortably fit in the wing. If this is not going to be a competition plane, 5.5 would look pretty good. Another piece of info is that the strut compresses 6" when sitting on the ground. The distance from the pivot point of the gear to the center of the axle when fully extended is 57.727" and on the ground is 46.727", and the strut is 44.727" when fully compressed.

Props4ever

Hey,

Mine have fixed double wire gears, so no retracts, struts, oleos to worry about.

Well i'm trying to see if a friend has 6" wheels, if not then 5.5" Dubro inflatable wheels will do the trick for me.

checklist123

Can someone specify the diameter of a p51 full scale external strut?
please