DHC6

My Feedback: (6)

I am working on a friends BVM ARF Mig 15. He purchased it a few years ago, and it's time it flew! So I am I the process of going through the aircraft and setting it up.

However when I removed the top cover I found that the turbine/bypass is not mounted to anything. It's just siting in the fuselage lose. Even stranger is that I don't see any broken mounts or anything that looks to be missing. I have ordered a new manual, but won't get it for a few weeks. Can anyone with the Mig show me how your turbine is mounted?

ravill

My Feedback: (11)

If I were a betting man, and looking at the bypass install on BV's website, I'd bet that the bypass sits on one of the formers (looks like the rear one) and attaches with a plastic L to that former. The front and rear of the bypasses will be connected to the ducting and he pipe, respectively.

JackD

My Feedback: (4)

Yeap!!

DHC6

My Feedback: (6)

Ok thanks guys. I am trying to find something on BVM's site, but can't seem to find anything. Anyone have a moment to have a look and post a link? I will also have a closer look under the bypass to see what I can find.

JP-1

This may help, post #56:-

http://www.rcuniverse.com/forum/rc-j...5-build-3.html

Alistair

smiller

The bypass screws onto blocks that are glued to the bulkhead that the bypass sits over. Tabs on the bypass are where the BVM engine mounts are attached to. Hope this helps.

Scott

DHC6

My Feedback: (6)

Ok, I figured out what's going on here, and it's pretty disturbing... Looks like the previous owner was having CG issues and decided rather then move other components around he moved the whole Bypass/turbine back. The mounting tabs were behind the fuselage former, and not attached to anything. Under the bypass tube he glued a tinny pice block of ply to the fuselage former, then screwed, with one tinny screw, the bypass tube to the little block. I guess in shipping the little block, (and I mean little, less then 1/2'' thick, by 1/2'' wide by 1'' long) broke, because it was only CA'ed on. Can you imagine if that came lose in flight? You'd have a large CG shift, coupled with uncontrolled thrust vectoring... Guess this will be a full tare down now to see what other supprises lie inside... Also looks like the aluminum bracket is missing as well...

JackD

My Feedback: (4)

can you send a pic? the tabs don't attach to anything. The bypass in BVM planes is usually held by:
1) front against intake (silicone glue)
2) bottom screwed agains blocks that are ussually glued against the former

That's it. Doesn't sound like a lot, but it has been proven successful for a couple decades

Not sure how the previous owner might have shifted anything back, since the distance is defined by the lenght of the intake. And also, Migs need nose weight,

Send a pic, we will help (I own a Mig)

Jack

DHC6

My Feedback: (6)

Ok so here is what it looked liked. If you notice there are no screws it because I just set it all back in now to take the pictures. But this is exactly the way it was.



Here you can see how far back it was.



Here is the tab behind the fuselage former



This is where the little block was glued



Here is the little tab I am talking about on the bottem of the bypass tube



This one is hard to see, but that little spec next to the light refelection, that's the tiny little screw that was holding the bypass tube to the little block. Which also the screw head made a dent in the engine casing...

roger.alli

Hi

From you photos, it looks like your motor/bypass is positioned far too rearward.. The front of the bypass should be moved forward, to connect to the inlet ducts. Making one continuous smooth air way through the model.. (Your exhaust pipe may be too short if this, is the case.)

This photo (from the Mark S Mig 15 thread) shows the correct position of the bypass.



As Jack D states, the bypass/engine combo is only retained by… 1): Silicon glue of the bypass to inlet joint, and 2): Two screws at the bottom of the bypass. These screws are (in most BVM kits) attached to a black plastic “L” bracket which is fixed or glued to a former. (Doesn't sound much, but it works.). This pic, (of a UB bypass) shows the brackets and a similar set up.

I recommend you obtain a manual as the instruction will detail this very clearly...

These are great models.



These are great models. You will love it..

JackD

My Feedback: (4)

OK... you are right, that is completely wrong.

The weird thing is that I don't know why would you need to move the turbine backwards on a mig, since it is usually a tailheavy plane. Maybe he didn't have the correct pipe?

You will need a new pipe, and follow what Roger just shared. It is actually a simple install.

One more thing: there should be a bracket on the top of the fuse, bringing continuity to the rear former. That's an important one. Make sure you have it

good luck
Jack

DHC6

My Feedback: (6)

Thanks guys I do have the rear bracket, just removed to take out the turbine. I have herd a lot of good things about this Mig. Looks like a lot of fun to fly, I am sure the owner and I will enjoy flying it, now I Just need to sort it out and get it airworthy.


Yea, still not sure exactly why he did that with the turbine... I will put it all back as per the book and start fresh. I have a manual on order from BVM, I will pick it up next week when I go to Florida for vacation. Wonder if they sell the parts that are missing, if not should be simple enough to make up.

The pipe as it is now, sticks a fair amount out form the back, so maybe it's ok? Comparing from the pictures in the build thread this one is WAY to far out as well. It out a few inches past the fuselage.

roger.alli

Sounds like you have it sorted now.. I am confident BVM will have all the parts you need.

If you are planning to visit their factory, make sure you let them know in advance. They will likely be able to show you factory model bypass set up and answer any issues.


Roger