RE: Venus II

RE: Venus II
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RE: Venus II - 7/20/2008 6:58:52 PM

TomTreese

Posts: 421
Joined: 7/30/2005
From: Williamsburg, VA, USA
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Would you recommend the Dubro Vibration Mount??

http://www3.towerhobbies.com/cgi-bin/wti0001p?&W=000716265&I=LXD633&P=K

The size a weight of the 150 is actually smaller a less than the OS 120s.

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Post #: 776

RE: Venus II - 7/20/2008 11:19:40 PM

Don M.

Posts: 1770
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From: Halifax, NS, CANADA
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quote:

ORIGINAL: TomTreese

Would you recommend the Dubro Vibration Mount??

http://www3.towerhobbies.com/cgi-bin/wti0001p?&W=000716265&I=LXD633&P=K

The size a weight of the 150 is actually smaller a less than the OS 120s.

That's the mount I have in my Venus II ( OS 120FS ) 300+ flights and going strong. Actually my mount is the #686 which has the same rails as the 688 but a smaller footprint. A-1

P.S. I have not even changed out the rubber grommets yet. Maybe in another 100 or so flights.

< Message edited by Don M. -- 7/20/2008 11:21:30 PM >

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Post #: 777

RE: Venus II - 7/21/2008 4:11:40 AM

codfish

Posts: 87
Joined: 3/13/2006
From: sellersville, PA, USA
Status: offline

quote:

ORIGINAL: TomTreese

Would you recommend the Dubro Vibration Mount??

http://www3.towerhobbies.com/cgi-bin/wti0001p?&W=000716265&I=LXD633&P=K

The size a weight of the 150 is actually smaller a less than the OS 120s.

I hate to rain on anyone’s suggestions and that is certainly not my intention, but I think it prudent to let you know I have had problems with the Dubro anti-vibration mounts. Some vibration mounts actually increase vibration. this was my experience with this mount. In this application I used the mount for a 2 cycle engine with a remote needle valve assembly. The vibrations were amplified so much that it actually cracked the remote needle assembly which was attached to the engine. After going to a solid mount the vibrations decreased and the new needle valve assembly did not break.

In another application with a Saito 100 I still wanted to use the dubro components to provide vibe dampening. In this application I increased the firewall thickness enough so i could mount the vibe dampening grommets and aluminum spindles directly into the firewall. I then used a standard mount and screwed it in through the vibe dampening spindles and grommets. My reason for this approach was that the Dubro mount can act like a cantilever increasing vibes. This is all affected by the actual frequency of the vibration. This seemed to work well, but is allot of work and extra weight. If i were to do it again id use a Hyde mount. They are expensive, but there is a reason for that. They are constructed radically different than the Dubo vibe mounts. No cantilever effect and very wide surface contact area make this mount the one of choice. If using a Hyde mount you must specify the type of plane you are using since the nose ring must be built into the mount itself.

Vibration dampening if done wrong (cheaply) will cause more trouble than it aleviates.

DonM has been happy with his setup so I'm not saying they can't work, just don't be surprised if you get effects you don’t desire.

(in reply to TomTreese)

Post #: 778

RE: Venus II - 7/21/2008 4:38:35 AM

pappy35

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Joined: 10/30/2006
From: Liberty Township, OH, USA
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Though I haven't had any failures, I don't think those mounts are well engineered. The torque pulses are what we're fighting and that kind of isolating mount is mean for low-amplitude, high frequency vibes. For you engineer-types I mean a rotating radial force vector like that caused by an out of balance prop.

I initially installed one of those Dubro mounts and very quickly wore out the isolators. I went back to the solid, glass-filled type and the airplane seems happier for it. I think that Merle Hyde got it right with his mount. It's designed to dampen shocks in the props plane of rotation - a rotating circumferential force vector.

Sorry...too many big words...my head hurts now.....

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Post #: 779

RE: Venus II - 7/21/2008 11:40:27 AM

Don M.

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From: Halifax, NS, CANADA
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Now what in the world do you think the difference is with my planes. I've used these mounts exclusively for 10 years now and have had them in about 10 different airframes I even used one on a 26 cc gasser with a full length tuned pipe. I have ALWAYS been satisfied with the vibration damping, have never had a failure of ANY kind ( mount, airframe, servos, switches, etc. ) and after a total of at least 2000 flights have NEVER replaced any of the isolators or have never seen anything but exceptable wear on them. My Venus has the canopy and cowl screwed on with servo screws and there is next to nil wear in any of the holes.

I'm baffled

P.S. I decided after I wrote this to pull the cowl on my Venus and check. I have 307 flights on this set up and over 100 since I pulled the cowl. The mount and isolaters are like new ????

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< Message edited by Don M. -- 7/21/2008 4:12:30 PM >

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Post #: 780

RE: Venus II - 7/21/2008 6:41:14 PM

codfish

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From: sellersville, PA, USA
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Don,

Nothing is different with your planes. You have just had different experiences with your vibe dampers than we have. If it works for you and you are happy with it then don't worry about it. Nothing wrong with that. The Venus has a very strong firewall and joining the fuse. If in fact you are increasing your vibes rather than reducing them, the Venus may be able to handle it without incident. The only way to tell is with vibe sensors. (which most of us don't have).

I think the Venus II is strong enough that vibe dampers are not needed. So for anybody confused about which way to go with vibe dampers, just forget about them, use a hard mount and save the $$$.

(in reply to Don M.)

Post #: 781

RE: Venus II - 7/21/2008 11:26:37 PM

TomTreese

Posts: 421
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From: Williamsburg, VA, USA
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Now I'm really confused.

I Just sent a Saito 180 back because the exhaust pipe and manifold keeps coming loose and it finally stripped the threads in the cylinder head. I read on the Saito site,: http://saito-engines.info/engine_mount.html, That alluminum mounts may be better for the 150's and 180's? but those mounts are not the Dubro Dampening type? I asked the Saito technician today and really didn't get a definite answer.

I just found an article in December 06 Model Airplane News by Chris Chianelli that states: "Fiber filled mounts serve to exacerbate the vibration problems intrinsic to 4-strokes simpley because they flex too much".

If that is so, why would you want rubber grommets in the mount??? Would they add or subtract from the vibration??

This is Important not only for the Venus II I ordered but also for the Ultimate I'll be reinstalling the 180 on?

Help!!!

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Post #: 782

RE: Venus II - 7/21/2008 11:56:46 PM

Don M.

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From: Halifax, NS, CANADA
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I can only offer my 10 years of observation while using them as stated in my post # 780. Buy one, try it and if you don't like it through it in the garbage. None of mine are for sale

I also had a Dubro mount in a Goldberg Ultimate / OS 1.08. 1100 flights and the isolaters were worn out but still in there. Oh yes, after 1100 flights it still had the same cowl, same wheel pants, same servos, same switches. I did wear out 2 batteries and 2 sets of crank bearings though

I never had a 180 but I understand they can be a "shaker" maybe it might be better to mount it solid.

< Message edited by Don M. -- 7/22/2008 12:49:37 AM >

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Post #: 783

RE: Venus II - 7/22/2008 1:35:16 AM

nonstoprc

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Post #179 at http://www.rcuniverse.com/forum/m_5469339/anchors_7751598/mpage_8/anchor/tm.htm#7751598 shows a home-build hyde soft mount, for 40CC gas engines.

Just another option for soft mount.

(in reply to Don M.)

Post #: 784

RE: Venus II - 7/22/2008 2:04:59 AM

TomTreese

Posts: 421
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From: Williamsburg, VA, USA
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DonM, Thanks for the help.

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Post #: 785

RE: Venus II - 7/22/2008 3:51:14 AM

cmoulder

Posts: 509
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From: Ossining, NY, USA
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FWIW, I have been using the GP fiber-fill mount that came with the plane and it's still going strong with the OS 1.20 FS. I don't know how many flights, but like Don M's it's gotta be in the 300-ish range. I flew it 11 or 12 times this past weekend.

This is a pretty stout airframe and will probably work well with just about anything.

A LHS guy said that glow fuel prices are about to skyrocket, so I may be going all gas (with a little electric) soon anyway. Maybe Saito will come out with a little brother for that FG-36.

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Post #: 786

RE: Venus II - 7/22/2008 9:26:12 AM

Don M.

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From: Halifax, NS, CANADA
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I just bought the last 2 cases of CP 20/20 that my LHS had @ $27.00 + tax a gallon. He has more on the way in and it will be at least $35.00 + 13% = $39.55 a gallon. There ain't no way in H - - - I'll pay that. I've discovered electrics over the last 6 months and dabble in gas. If the prices stay up I'll be giving up glow. I'm already sizing up the Venus II for an E-Flite 1.10 next winter.

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Post #: 787

RE: Venus II - 7/22/2008 5:26:37 PM

codfish

Posts: 87
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From: sellersville, PA, USA
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The Saito 180 really does have problems holding onto mufflers. I know of people with the same problem which never got resolved, even with Saito's help (of what help they really are). Our field is littered with lost pipes and mufflers, but none of them mine!

I recommend forget using vibe dampening with the Saito 180 and just use solid aluminum rails. The idea is to transfer the vibes to the frame, forcing the engine to be more solid, let the frame deal with it to protect a poorly designed exhaust system. I share your pain with Saito's engineering