MTK

Bob and Gungadin,

The studs that hold the choke on the carb are actually inside my soft mount. If you keep the whole engine outside the mount or if you hard mount on a firewall and you don't want to cut a hole in the firewall to clear the studs, then a little over 6" is the correct distance to the prop drive washer.

BTW, I don't think I mentioned that in my test bed the firewall has been cut to mate with the soft mount's hole. The carb is actually taking some air from inside the fuse. On the test bed this obviously wasn't necessary but I've wanted to do that on other stuff so why not test it in the test bed? Even though the balsa/-/carbon firewalls I build are very light, this would save about another 15-20% of the weight of the firewall.

Don't fret the motor box face too much. The soft mount absorbs so much vibration that it is a non issue. If you hard mount that may be another story though

It isn't that difficult to drive the choke with a servo. First, you need a 90 degree belcrank with a long and a short arm and second, you'd need to clip the arms of the spring but save the barrel of the spring. That would push the baffle down onto the carb but have almost no resistance without the arms. Drive the short arm because the long arm needs to move about 1 1/2 inches. I am thinking about doing precisely that on mine.

MattK

cmoulder

You're using a choke servo??! Something like a HS-85MG? Sounds workable, the way you describe it, but won't the rotation from the soft mount stress the servo?

Man, I really want to see pictures of that arrangement![8D] I've used a choke servo only once and it really is convenient to handle it with a servo... albeit with a weight penalty.

Unless there is some compelling reason, I think I will not make a hole in the motor box because without a carb stack the carb tends to spit out a bit of gas, which over time adds up. At least that's been my experience with other gassers.

Dan, the Focus motor box sticks out more than 2-1/2" from the firewall, so either you will have to modify it a bit (heh, what else is new?) to shorten it, or use the short stand-offs and make clearance in the firewall for the carb. Much easier to shorten the motor box, IMHO. For 6" (plus a smidge) prop drive washer-to-firewall, the actual stand-off measures 1-15/16". This means the stock Syssa stand-offs for 6.25" will measure very close to 2-3/16" (for the stand-offs themselves).

I'll post some pics when I actually get cranking on this.

Gungadin

Thanks Matt & Bob for your input. It will all come clearer to me when I actually have my engine & plane in hand, but you guys are great helping me get a mental picture ahead of time. Thanks again.

cmoulder

Got some more done today, specifically the part I usually dread most - mounting the engine, and getting all the thrust angles to come out right with the prop thrust washer in the center of the cowl exit hole and without too much or too little clearance for the spinner backplate.

Did a bunch of measuring for the motor box to see how much I'd need to trim off, and in the end I missed it by about 3/32", but this ended up being no problem because it was easy to fix.

Glad I used only 3 bolts for the soft mount to attach to the motor box. I intentionally wanted the stance to be narrow, and even then I was able to get the outermost blind nut into the motor box, though it took some work with the Dremel router.

The motor box was very weakly glued, so I had to remove the worthless balsa triangle stock and the hot glue, and re-do it with some square beech stock, small wood dowels, epoxy and screws.

The engine fits completely within the cowl, and all that will be needed is a cut for the spark plug cap and of course the air exits, a little hole in the side to access the needles, and maybe (or maybe not...) a hole in the bottom for the choke rod.

MTK

Very nice fit Bob,

One thing you might consider is to either find or make a small bracket that can secure the Hall sensor wire. I made one from some steel sheet stock I had on hand. With the engine shaking a little on the soft mount, it's probably a good idea to support the wire. I have my bracket mounted off one of the backplate bolts

Matt

Gungadin

Great job there Bob ! Looks like you added down & right thrust, no ?

cmoulder

Hehe, thanks, it did come out pretty well, but there was a whole lotta cussin' during the process.

Yep, I've got a long way to go to tidy up the wires and figure out where everything will fit (read: ignition box!). Received in the mail today the Tech-Aero switch/regulators and they are beauts, very light and perfect for this application. Got a couple of FlightPower 800-mah 2S Lipos ordered for Rx/ingition. Using the Syssa IBE but didn't get that yet.

The next problem I don't know exactly how to handle is the header. With the right and down thrust of the engine, it exits in the pipe channel but nowhere near the middle where it can be easily connected to the ES pipe. So it is either going to have to be bent or, more likely, split between the exhaust flange and bend with a very short flexible coupler installed. Flexible coupler seems the easier way to go, which begs the question, what is used for a gasser exhaust coupler so close to the engine exhaust port??

MTK

Bob,

What I do is bend the header to fit. You'd need a vice, a berzomatic and a piece of aluminum that you can drill and tap. The idea is to secure the header to the plate and the plate to the vice. Then gently heat the aluminum tube at the straight section and apply appropriate pressure. It's a five minute job

Matt

cmoulder

The motor box has 1 deg down and 3-1/2 deg (!) right built in... A LOT! I left the 1 deg down but had to reduce the right to about 2-1/2 deg to get the soft mount to fit on the motor box and have the prop bolt exit in the middle, and even then it juuuuuusst fit. Later maybe I will have to do a throttle-rudder mix, but not much option. Might end up needing none, who knows?

Probaly not an issue at all when you hard mount.

MTK

Oh yeah, and if you look at one of the posted photos on page 3 or 4, you'd see the coupler I use. I think I talked about that before...anyway, it's a length of fiberglass that is teflon clad and has silicone adhesive on one side. From McMaster Carr....I roll my own

Matt

Gungadin

Matt-Are you saying, bolt the header via the exhaust flange to the alum. plate ?

MTK

Yes that's how I do it. Heating will soften the metal just enough. You don't want to overdo it because aluminum melts at 1100 degrees. But it becomes very easy to bend at around 700-800. I cool it at room conditions, no quenching necessary

ghoffman

My Feedback: (3)

Ok, I apologize in advance if I missed the post, but why do you need the soft mount?

cmoulder

Yes, I have that tape already, for the header/pipe coupler, but somehow it seems it might not work quite so close to the engine exhaust port.

I know you don't have that many flights with it, but is that tape holding up well so far?

cmoulder

The idea is that - in combination with the tuned pipe and the appropriate prop - it helps reduce noise quite a bit. My first home-brewed soft mount, so I don't actually know yet!

cmoulder

Just looked at Home Depot website and they have standard, pencil and micro torch heads, propane and butane. I'm assuming standard torch head w/propane?????

alpoman

Hi, All. Just want to update the note that my friend RC11 put here about our maiden startup up of my SAP 180. The problem was not the engine but the carb. It would not draw fuel as it should. I have a lot of years working with engines and before I got discouraged I called Todd Syssa and got no answer. About 10 minutes later Todd was on the phone calling me. We chatted for quite a while about all of the possibilities and I decided to tear down the carb and clean it. After a total carb disassembly I found nothing wrong so I blew it all out with compressed air and put it back together.

The carb works fine now and pumps as it should. So dirt somwhere had done me in. These things are usually the simple stuff. Todd runs the engines before he ships them so I must have got dirt in it some how. It is not the first self inflicted problem I have had over the years.

One great note of interest is: How often have you had a problem with an engine and made one phone call and in 10 minutes the designer, and manufacturer was on the phone calling you back to resolve the problem? I'll bet never!

Thanks for your support Todd. Product and support like this is the type of thing that will get our economy back on it's feet.

Happy New Year to All
Dave

MTK

Yes, that's plenty of heat

NJRCFLYER2

My Feedback: (42)

Alsp, you get less consumption from the batteries each flight, so you can use smaller capacity batteries. You get less current consumption because the airframe is doing a whole lot less shaking, so there is much less work for your servos to do to keep the control surfaces from shaking around. Finally, the airplane and everything in it lasts longer, since they are not getting beat up. Soft mounts pay for themselves in many ways.

cmoulder

Oops I forgot about that part! Hyde's ads claim very large drops in current drain, and there is plenty of independent evidence I've read to back it up.

The Focus Sport was the first plane I used one on (Hyde plus home-made nose ring), and while the plane does of course vibrate, it doesn't have that harsh edge to it like a hard-mounted engine would cause. I do have a comparison there because I had a Venus II with a hard-mounted OS 1.20FS. Big difference.

MTK

I think I may have mentioned that I am still using original, never serviced servos in my primary plane. Temptress has something like 1500 flights on her by now over the past 6 years give or take. Never have changed the pots, gears, whatever, in them and the mount is the reason.

The planes shake at idle, true, but it is at a much lower frequency than the 2000 rpm or so of the idle. At high revs, the planes don't even shake. Touch the aileron at the tipe and you will feel the difference.

Matt

LCHelilover

My Feedback: (15)

Bob,

I have found with my gas OS 160 conversion that standard teflon tubing type connections burn through quickly. I have have had much better luck with machined teflon couplers which are holding up very well. Other alternatives are: 1.rolling your own coupler with beer can aluminum and RTV silicone ( I made one but haven't used it yet, cause the machined teflon is holding up so well). 2. Using teflon/fiberglass/silicon imbedded tape to roll your own or reinforce an existing coupler as metnioned from McMCarr. ( I got some of this but haven't needed it yet either).

George.

FlyEng

My Feedback: (5)

I plan to undertake manufacturing my own softmount, too. My installation of the SA 180 will also be in a Focus (ARC). What outer diameter would you recommend for the softmount so that i'll have no issues with it conflicting with the cowl?

And just to be sure, the glue on the rubber only goes on the cut edge or can it bleed under just a little? I get how it works and really appreciate you guys taking the time to post.

-D

cmoulder

Okay, thanks George, I'll definitely keep that in mind.

However, I was in Home Depot with a honey-do list early this morning and picked up the bernzomatic propane torch as suggested by Matt. I don't have a vise, so I used a couple of strong C-clamps to anchor the header flanges to my outdoor grill, then heated with the torch and used a piece of metal rod to bend the header pipe. Miraculously, I got the left-right bend (perpendicular to the mount flange) perfect on the first try. It took about 3 tries to get the outward bend (away from the fuse) correct, but it is right on the money now. Bolted it to the SAP 180 (after drilling out the flange holes a bit!) and it exits dead center in the pipe channel.

I know at some point I will have to use a Teflon-type coupler, but for now this is excellent. Adds no weight and doesn't introduce another point of potential failure. Using the tape you mentioned for the header/pipe coupler.

cmoulder

I'm at work and not home 'til late, but I will measure and let you know. Mine just barely has enough cowl clearance on the left side of the firewall, and it is less than 4" in diameter. So for the Focus it is somewhat critical because it has a lot of right thrust built in, some of which I had to remove. You might have a little more flexibility with the ARC, but at any rate you won't have gobs of room to play with.

P.S. [link=http://www.rcuniverse.com/forum/m_6285026/tm.htm]HERE[/link] is MTK's thread about constructing the soft mount.