gauravag

Hello,
I have a Saito 125 mounted to my Javelin 90 pattern-like airplane. Currently it has solid aluminium mount that is directly bolted to the firewall. Though i have had 20 or so flights, i note that there is considerable vibration ( prop is balanced ) . Was wondering if i should try and change the mount to Dubro Soft ounts ( that has those rubber isolators ) .
Did a few searches, and noted that many people were against using Soft mounts specially on 4 strokes. Would it be safe to use these ? I do not want to reduce the life of my engine, but can spare some rpm if i can live with reduced vibration.
Thanks for sharing your views.
gaurav

oldvet70

My Feedback: (10)

The DuBro 688 mount can be used with that engine. You did not say if you were concerned about the engine vibrating, which in my experience Saitos do until well broken in, or if it is transmitted vibration to the airframe. If it is vibration of the airframe it should help but if its just that 1.25 doing the Saito shake , well that will probably lessen after a few gallons/hours on the engine.

airbusdrvr

It is about now in your running of the Saito 125 that you should also recheck your low speed needle (low speed mixture). As you would with most engines, lean the low speed needle until when at idle rpm you pinch the fuel line you get no increase in rpm. Then richen the low speed needle until you do get a slight rise in rpm when the fuel line is pinched. Then if the engine accelerates well from idle you are good. I found this made my Saito 125 seem to run more smoothly with less vibration.

gauravag

Yes, i am concerned about the airframe vibrating. The engine does not vibrate that much, but it somehow seems to get transferred to the airframe a lot.
I do have the low end needle set, and the engine so far has around 2 gallons of fuel through it. I want to fly this plane regularly to practise pattern, and since the Hyde mount ( which is claimed to be the best ) is not available to me, perhaps the Dubro soft mount would better than the stock hard aluminium mounts.

The information i was looking for here was, if there are any drawbacks to using a soft mount over a hard mount ? Any detrimental effects on the engine/life or flying performance ( some claimed thrust line changes )

Thanks to all
-Gaurav

oldvet70

My Feedback: (10)

Given you are concerned with transferred vibration I believe the DuBro mount will help. I don't believe it will shorten the engine life and if properly installed it will not cause any flying issues either.

Hobbsy

My Feedback: (102)

Most Saito shaking is not actual vibration unless as mentioned above, the LS needle is too rich. Most of what your seeing is the result of tortional impulses which are the result of a light engine and strong power pulses. A soft mount will exaggerate this. Running a prop like a Graupner 15x8 will help as it has some weight to it.

MartyH

My Feedback: (16)

I agree with the heavy prop idea. I don't like the idea of a soft mount on a Saito. You could hit a resonate frequency and watch the front of the plane shake apart. Anyone I have known that has used one with a 4-stroke either removed it after trying it or it removed itself in a few flights.

Charley

My Feedback: (2)

I've had a Saito 1.50 on a soft mount for years with nary a problem. Lucky me........

CR

Waco

My Feedback: (265)

I have been using the DuBro soft mounts for 4 years now with no problems yet, if fact I like them and would not use anything else, I used them on a saito 150, a 100, a 91 with no problems. I had a friend with a hard mounted saito 91 and it had a lot more airframe noise than mine with the soft mounts.

blw

My Feedback: (3)

I have a Saito 1.25 on a hard, GP mount and it is very smooth. Hobbsy is right, if your Saito shakes you should spend time with the tuning before anything else. If it shakes and you get the soft mount, you are only masking the problem.

Hobbsy tunes his HS to peak and leaves it peaked. Then, he tunes the LS. I go about 1/8 to 1/16" turns lean until the model shows signs of not being smooth when I slowly advance the throttle. At that point, I richen by about 1/16". I try slow throttle and it if holds that, then I go wide open quickly. When the model holds that, I fly it. You have to listen to the engine when it is flying before saying it's tuned.

earlwb

If you want to use the soft mounts, go for it. it won't hurt anything.it does change the vibration mode resonances and that means lessvibration getting through to the airframe. it is pretty cool on somemotor mounts to see the engine wiggling more at idle. But as soon asyou give it the throttle the engine smooths out. So no big deal. Iflater you decide you don't like it. You only have the hassle of fillingin the mount holes and redrilling for a regular motor mount.
I used them in the past to good effect. They don't affect anything. ifanything you get a longer airframe life as there is less vibrationstressing the plane and the radio control system parts, etc.