ORIGINAL: cmoulder
ORIGINAL: Gungadin
Yes, I guess so, since the engine rear prop driver washer should be the same in relation to the front of the cowl. Only difference will be our stand off lengths cause yours has to take thickness of the soft mount into account and mine will probably go direct on the firewall.
Hmm... later I will do a couple of measurements to see what length stand-off's would be needed for hard mounting the SAP 180. The total length of the engine - from the prop drive washer back to the 2 studs that hold the choke plate - is right at 6 inches, maybe just a tiny bit more, but not much. So if you don't want the carb to protrude back into the motor box, that is the minimum. And really you don't want the carb to protrude past the motor box because the Walbro carb on the SAP 180 has a funky choke plate that I haven't seen before, which is literally a stamped metal plate that is spring loaded and rotates on a stud with an arm sticking out, and the other stud serving as a stop. (Glad I'm using a choke rod, so I don't have to figure out how to link a servo to that thing!) Also, since the motor box face isn't very robust, you want to leave as much material intact there as possible.
The motor box on the Focus II sticks out pretty far, so even with the minimum ''carb-clearance'' standoffs you may have to modify the motor box to shorten it somewhat. Firewall to cowl exit is 7-7/8'', which is the magic number.
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