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Warbirds Replicas P51 Mustang


RICHARD WILLS

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Good morning fellow Balsa (that was) bashers.

For those among us that are going down the sound system route.

So far there is two methods to date.

1. Richards..... Easy

As per page 13 of the MANUAL the bottom block of balsa can be swapped for a suitable piece of depron, to the inside of this you can glue the transducer. Fix in place as you would the balsa block, sand to shape and cover as normal.

We have both found that if you try to fix the transducer to balsa/ply the volume is no where as good as a piece of depron.

Also should you need access to the transducer it would be simple to remove using a scalpel

2. Mine....... Not so easy, Why?..... because I cancheeky

Now as you recall I did not glue in the battery box and this is the route I have chosen.

I made two ply side supports which are fixed inside the nose running between the first two formers, these have fitted M4 threaded inserts. Holes were drilled into the battery box sides. this allows me to fix the motor/battery box securely in place but will allow easy removal if required in the future.

This stems from my paranoia of "if I can't get to it.... I'm gonna need to"

I will use the balsa block but have decided to create a circular hole in the block and on the exterior cover this with some very fine stainless mesh set flush with the exterior surface to be painted to blend in but create a sound outlet to try and enhance its tone.

Internally I am going to mount the transducer on a piece of depron affixed just above the balsa block.

I am hoping this will create a sound box to enhance the bass a little.

I haven't tried it as yet but this is my plan.

I will put up a quick video of my findings when I get that far.

But this is what has been completed to date.

Side supports with 4mm inserts glued in place.

battery tray fitting1.jpg

Motor/battery tray refitted.

battery tray fitting 2.jpg

Access available after removing tray/motor.

battery tray fitting 3.jpg

I intend using the tops of the 12mm square section to glue the depron sheet to to create that speaker surface.

Lets hope is is worth the effort!!

3. Method 3

Add your ideas here........!!!!

4. Anybody found a 1/8 scale Packard Merlin?

 

Edited By Paul Johnson 4 on 08/11/2020 09:14:12

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David is right about the X mounts . They dont come with the motor .

I am not supplying motors this time as its a pain .

The NTM 650 does come with a mount and if we are all struggling , I will get the machine shop to make some X mounts for the predator .

As usual its half a job from everyone else , which is why it takes so long to put a proper kit together ,

Dont panic chaps we will get round it , All keep your eyes peeled .

Richard

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Nice one Richard. I've got three of those NTM propdrive v2 4248 650kv units from HobbyKing and like you said, the bolt on prop adapter is just too short. I have also gotten my hands on 3 of the dynam 13*7 3 bladed props and there simply isn't enough thread to accommodate a spinner backplate and get the prop nut on too with the depth of the prop hub.

I'm going to see if I can get one of the guys I've met from my local club to fabricate some as he's a world class model maker and has CNC machines coming out of his ears...

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When you say ....confoosed . Do you you mean that we should refer to you as "Doreen" at the weekends ?

No. that is just a nice way of holding the shell of a spinner on , it will not help with the lack of prop shaft .

What we need to solve the problem, is for the nut to have a "sleeve " that can reach backward toward the motor and then you simply countersink the front of the prop hob so that the nut can grab some more thread ,

If you have a lathe it is easy of course . You just take a regular 8mm prop nut and turn half the hex off so that the part you will spanner is half the width and the rearward part is a smaller diameter tube with the original thread still inside ,

An OS 52 FS nut has the same principle .

I will try to post a picture in a bit . Even without a lathe , the same can be achieved with file .

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Right chaps I was beaten to it by Paul, who wasn't supposed to fit his "precious" spinner this quick. All those who ordered the spinner will receive Four prop shims to overcome the clearance fit. I will get your addresses from Richard and post them direct to you. Just place them under the root of the blades and it will raise the blade by 3mm. I was a bit overwhelmed with printing the cockpit kits but have caught up now.

a.jpg

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Posted by Glynn on 10/11/2020 17:44:28:

Right chaps I was beaten to it by Paul, who wasn't supposed to fit his "precious" spinner this quick. All those who ordered the spinner will receive Four prop shims to overcome the clearance fit. I will get your addresses from Richard and post them direct to you. Just place them under the root of the blades and it will raise the blade by 3mm. I was a bit overwhelmed with printing the cockpit kits but have caught up now.

a.jpg

Is that for if you are planning to use the FMS 4 blade prop? The Dynam 13*7 3 blade has about 1mm clearance from the backplate of the spinner thanks to it's fat hub.

Forgive me, I just read back a bit and spotted that's exactly what they're for! OK, move along, nothing to see here...

And in my defence I have two of the spinners and was going to use one of them for the Spitfire, although now, looking at the spit spinner, it's different. I think I need to lie down...

Edited By David Hazell 1 on 10/11/2020 18:11:44

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Thanks Glynn, splendid service.

So, with the aid of Glynn’s shims (sounds like a brand name for I don’t know what?), the FMS prop blades bolt directly onto the spinner backplate. What goes in the middle? I see that, with the FMS plastic 4-blade spinner, there is a circular clamping piece that goes over the blade roots. I’m guessing that with the sturdy alloy spinner backlplate, this clamping piece has been deemed unnecessary, but there is an unthreaded section on the Predator motor’s prop driver that would surely still need a bush or spacer of some sort.

Paul, any chance of a pic of your prop installation with the spinner cone removed?

On the issue of the motor cross mount, does anyone know what the hole spacing is on the back of the motor? I do have a couple of cross mounts in the spares box and I’m feeling lucky today

Thanks in anticipation,

Trevor

Edited By Trevor on 11/11/2020 11:06:35

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Posted by Trevor on 11/11/2020 11:05:12:

Paul, any chance of a pic of your prop installation with the spinner cone removed?

Thanks in anticipation,

Trevor

Edited By Trevor on 11/11/2020 11:06:35

You want to see my Precious naked......????

Oh okay...

prop adapter.jpg

You will need to remove the hex section of the shaft, easily done by first filing the worst of it of then using a drill spin it up and run a file over it to finish.

The spacer is a bit of ally i had about with a 8mm hole in it cut to length but you can get creative with anything with the an 8mm hole in it, stack up some ply discs on an 8mm bolt and spin it up in a drill and sand to required size etc

I used some M3 nuts as spacers instead of Glynns posh bits

prop spacing.jpg

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Hi,

Hope you don't take this the wrong way, but IMHO I am not to sure if the nuts and screw head might cause point loading and possible stress failure over a period of time. Perhaps not too much of an issue if you check the screws every time you head to the flying field.

Do the blades normally sit in a recessed back plate that supports the blade fixings

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