Best / worst mounts?
 

Seeing how some kits supply an engine mount or recommend a system, what are the good and bad features of : single mounts, two-piece mounts, mounts with grommets, 2-stroke different from 4stroke? I am about to add an engine to my 4*60 and want to go to a reliable running engine and mounting system. I have built the kit stock as this is my first low-wing plane. Any help here is appreciated. Mikel-T

RE: Best / worst mounts?
 

Here is what little I have to offer:

For a .60 size 4 Star you won't need any vibration damping so keep it simple.
One piece or two piece both work fine if installed correctly. The 4-stroke mounts are a little longer because some of the engines have the air intake behind the head.
I'm sure you will be using a glass filled epoxy style which drills and taps nicely.
The only problem I've had lately is a one peice mount where I had to cut away some of the webbing between the rails at the back to get my OS 4-stroke to fit in.

RE: Best / worst mounts?
 

Well, I can answer some of these. Four-Stroke engines with the carburetor behind the engine require a mount with longer legs. Thus, the 4-stroke's prop washer sticks out further from the firewall.

Two piece mounts are okay, and usually absorb a little vibration. As such, they tend to work loose, so loctite the screws. Some of them have grommets, but I've never seen a one piece mount with grommets. Again, they're a vibration absorbing feature. Keep in mind, either the firewall absorbs the vibration, or the mount.

Your 4-Star is a sturdy item. You can use a two stroke engine with a two stroke mount, and be fine. No cowl nose to align with. The firewall will be just fine, it can take the vibration. On the other hand, if you wish to go with a 60 fourstroke, it will be just fine, too. I don't usually spend the extra money for the rubber grommet mounts, but with a fourstroke you'd need the longer rails of a fourstroke mount.

You can probably fly the 4-Star 60 with a .46, or a .61 twostroke, or a .52 twostroke, up to maybe a .70 fourstroke. You'll like the plane.

Good luck,
Dave Olson

RE: Best / worst mounts?
 

In terms of being solid, from best to worst:

Beam mounts
One piece metal mounts
One piece plastic mounts
Interlocking 2-piece mounts
Individual 2-piece mounts

Practically speaking, they all work well if you use them properly. You don't need vibration isolation for engines in the range you're talking about.

The best bet if you think you might be swapping engines in the same range is the two piece inter-locking mounts because you don't need to drill new holes in the firewall, but you may need to replace the mount if the hole for the old engine would weaken the mount for the new engine. Sometimes you can use the mount you already have and sometimes you can't, but mounts are cheap, so that's the least of the problems.

If you use a one-piece mount and decide to swap engines and the new engine won't fit the old mount, then you usually have to do surgery on the firewall which includes putting in new blind nuts. Sometimes that's easy and sometimes it's a real pain.

More about Engine Mounts

- Paul

RE: Best / worst mounts?
 

Mickel-t
Make sure the bottom and top of the rails are parallel.
The GP mount in my Supersportster was not.
This would prevent you from putting a nut on the bottom for extra support or in case the threads became stripped.
KW_Counter

RE: Best / worst mounts?
 

The glass filled nylon mounts that ship in the 4*60 kit (not sure if the same are in the ARF... I expect they are...) are GREAT!

Very sturdy and plenty long for up to a .91 4-stroke with ease. There is no good reason to get different mounts. I used a O.S. .91 FS (4-stroke) and 14X6 APC on my 4*60, which I put retracts in. A bit more power than needed.;) but it was the best engine I had for the aircraft. (My .60 2-strokes are getting old and unreliable not a great plan to keep using them. I don't have a .72 4-stroke.)

The only real problem with the individural beans by Sig... you have to be good at getting the holes straight. There's a trick that works EVERY time. :)

Bolt the engine to one rail... bolt the other (undrilled) rail to the model. (not having drilled the firewall for the second mount.)

Clamp the engine mounting flange to the secnd mounting rail with a Vce-grip (use a piece of wood to prevent maring the mounging lug)

Mark the firewall for the second engine mount.

Drill the firewall and bolt the mount n place. Now you can mark the other rail... pull the engine clear to drill and everything will line up perfectly.

You can do this before putting the firewall into the aircraft... or after the model is built. (but its harder to get the blind nuts in after the 4*60 is built)

RE: Best / worst mounts?
 

FHHUBER: Please say that again S-L-O-W-E-R. You lost me when you said now bolt the undrilled mount to the firewall ( That means I have drilled holes already?) DUH??? I'm confused...[:o]