Brison 2.4 has an aluminum plate screwed to the back of the engine that is used as a firewall (or stand-off) mount. I like this solution so my question is:
Is it possible to add the same kind of aluminum plate to the back of MVVS 1.5 replacing the original screws with a little loner ones? Is the engine case strong enough to handle this kind of mounting?

RysiuM

RysiuM,


MVVS don't currently offer a radial mount, for this engine.

There are, however, several commercial engine mounts, which span the required 50 mm (1 and 31/32" ) and can handle this engine.

I believe [link=http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXATG7&P=7]this one[/link] and most dual beam types will suffice.

I'm sorry, but it doesn't answer my question. I checked MVVS website already for all what they offer (I can read Czech).

My question was about adding a custom made back plate for the mount. WILL THE ENGINE CASE SURVIVE if the engine is mounted by these four back-plate screws? Valid answer is: "Yey", "Ney", or "I dunno"

Thanks
RysiuM

RysiumM,


This type of mounting is used on engines as an after-thought, without any 'beefing-up' of the crankcase bolt threads and bearers. I have not seen any damage done to the crankcase from this unorthodox mounting method (unless a crash occurred), but I have not seen it done on any MVVS 1.60 either.

The thread size of the back-plate bolts appears to be 3.8 x 0.7 mm (eye + vernier caliper estimate).

You may want to contact MVVS head engineer Mr. Josef Å*vajda, maybe even in Czech, and ask him directly, if this will hold.

The E-mail is; [email protected] .

You may want to ask him to select one of your 'valid answers'...

I just received a mail from MVVS offering the backplate mount. (I have never used the mounting lugs)
Will place a picture in an hour or two, (short of time right now)

The back mounts are available for the 1.60 and 2.15 engines, in red and blue anodize.
Since I started using these mounts, be it bell shaped or flat plate with stand-offs, I never used anything else. On all engines, from 1.5cc glow up to the latest 116 twin gas engine, which has this mount integrated in the rear cover.
Changing engines is extremely easy, when using standardized back mount hole patterns.

That's what I was talking about. Do you know weight, price and availibility?

Do you need to change screws for that mount? This size looks more like M4, right? I can't think of any reason to use some odd sizes.

RysiuM

Sent you a PM.
Knowing MVVS, the appropriate new screws are probably supplied with the mount. The original screws will be quite short to hold full strength in aluminium, though they may survive a test run.
The back plate mounts spread the load quite well over the crankcase. In a crash, the plate yields, and not the crankcase. Don't ask!
Thread is M4 (metric system). For odd sizes we Europeans look into the imperial system :-^

RysiuM,


If these back-plate mounts replace the original backplate and are not significantly thicker at the 'flange' area, I can see no reason not to use the original back-plate bolts.
They should thread to the same depth as with the original back-plate.

I also thought about the thread size, but this is what my 'Kanon' stainless steel vernier caliper reads. I also thought it was a 4 mm thread, but it appears to be slightly smaller.

I do not have a thread gage, so the thread-pitch is an estimate.

I responded

I don't think so. From the third picture you see the original back plate in place. And there wouldn't be a hole in th center, otherwise you will se the crankshaft through it

I don't know how long original screws are. If more than 15mm ther emay be OK, but if shorter I wouldn't use them. The longer the better as in crash they would spread the load along the crank case. I would rather have firewall or engine case broken than crankcase. This engine cost more than twice of the planes I am going to put it on.

Now I need this mount fast. If I don't get it soon, I will have to make it myself.

RysiuM

Here is a package snapsot of the 35cc mount
it contains the mount, screws, instructions and allen key.
distance back to front:
26cc 10.5mm (diameter = 85mm)
35cc 19.5mm (diameter = 95mm)
With appropriate holes drilled, the 35cc mount can also be modified for use on the 26cc.