Side Mounted Engine?

I recall that the old Fox 35s didn't run real well side mounted. Is that true of all (most? some?) modern engines? I've heard that the PAW engines run better side mounted...(anyone experience this?) and I've seen a couple of 45 degree mountings (Igor for example). Is side mounting the engine just an expedient for profile airplanes? Are the side mounted engine run problems on a typical profile due to vibration, or is there some other factor?

...and a related OTS question: Must the engine mounting orientation be duplicated from the original to be OTS legal? Could you put an inverted engine on a "Mars" for example?

>I recall that the old Fox
>35s didn't run real well
>side mounted. Is that true
>of all (most? some?) modern
>engines?

I can not comment on the above as I have no direct experience and don't want ro requote hearsay

>PAW engines run better side
>mounted...(anyone experience this?)

Yes...i have had no run problems whatsoever with sidemounted PAW engines and the only instance of me using one in upright configuration led to a series of misfires and buttock clenching momemnts when doing some overhead manoeuvres. Tony Eifflander of PAW fame no longer uses his own engines in upright configuration in his own design stunters...stuutering in overheads were the reason for dwitching to sidewinder set ups.

> and I've
>seen a couple of 45
>degree mountings (Igor for example).
>Is side mounting the engine
>just an expedient for profile
>airplanes?

There are some sidewinder configs in full fuselaged planes..I can't quote any models off hand.

Are the side mounted
>engine run problems on a
>typical profile due to vibration,
>or is there some other
>factor?

Con't know...

>...and a related OTS question: Must
>the engine mounting orientation be
>duplicated from the original to
>be OTS legal? Could you
>put an inverted engine on
>a "Mars" for example?

I always thought from my free flight experience that models should be 'as per plan'

>I recall that the old Fox 35s didn't run real well
>side mounted.

That depends on what you call "real well", and how old of a Fox also, I think. They ran just fine pancaked for their first decade, maybe decade and a half. I still haven't experienced that dreaded high outside turn burp that upsets so many Fox nay- sayers so much.

>Is that true of all (most? some?) modern engines?

My experience differs from that of a sizable portion of the message base in this forum, since I fly a great deal less at slower engine settings than at fast ones. I can and do fly aerobatics occasionally, and will slow down for it. My engines - old and new - haven't demonstrated a lot of objection to being laid over sideways. But there are stories in profusion about this or that Schneurle design engine that can be as cantankerous pancaked as any Fox 35. Take it on a case by case basis!
>
>Are the side mounted engine run problems on a typical
>profile due to vibration, or is there some other factor?
>
Frank Williams had troubles with his ST 60's some years ago and started mounting his engines sideways, but on the inboard side. A line of CL kits with foamie wings produced in Dallas featured inboard mounting setups, so there have been folks taking that route away from the problems they ran into. As I understand the various suggested causes, the biggest problem is engine designs that allow unused fuel to accumulate, and then in some particular attitude change, slosh that little puddle of fuel into the cylinder, where it threatens to put the fire out.

For the folks whose Foxes do burp, the fix is a strip of hardwood down the middle of the bypass, reducing the cross section.

>...and a related OTS question: Must the engine mounting >orientation be duplicated from the original to be OTS
>legal?

Yes.

The K.

I like side-mounted engines a lot.
I built 2 twin-engine stunters using this method, a ME110 from the Aeromodeller plans and an own-design full-fuselage stunter.
Both using OS MAX25 engines ( 20+ years ago...)
I did not notice any vibration problems..... I am not an expert so the problem may have been there without me noticing.....

>I recall that the old Fox
>35s didn't run real well
>side mounted.

Depends on your definition of "...real well". On many Foxes, there is just the suggestion of a hesitation during outsides, and it is quite easy to live with for most. I have gotten so used to it, I hardly notice. And they vary by model over the 50 years.

For some, however, just a little of the Dreaded Fox Burp is unacceptable.

Personally, I think most Foxes run acceptably mounted sideways. But no one accused me of striving Towards Perfection, either.

Johnson "S"s have this Big Time, by the way.

The only planes I've built with upright engines were those using Cox Black Widows. I've not had any problems running engines on their sides at all, but then I fly Combat, not Stunt.

Today, I flew my SMALL FRY (Ron Prentice design of 1947) with the PAW 09. Side mounted but built up square fuselage. The PAW turns 9700 RPM on a 8-4 Zinger wood. (Davis diesel fuel). Runs are consistent throughout. Wedge tank set exactly at the needle height.