Magne

Will you still have access to the needles?

Magne

MTK

When the engine is mounted in the plane, it will be inverted which means the needles will point up. I will need to locate them and drill access holes on the top side of the nose of the plane. I don't think that it's a big deal. A pair of rubber grommets will dress the holes up nicely

MattK

MTK

MTK

The rubber is easy to cut with a straight edge and new xacto blade in your knife. It takes a few passes but it works very well. Rubber must be well cleaned as I mentioned before. It doesn't hurt to touch the edge with a Dremmel drum sander to expose fresh rubber. CA glue works best on fresh rubber.

The weight on the thing is quite reasonable at less than 4 ozs.

I still have not run but will soon and post photos at that time

Matt

esamart

Nose ring does not have to be a circle. 270 decrees might be enough. Perhaps it is possible to build smaller mount for a censor to fit missing 90 decree space.

MTK

I got everything put together finally, and ran the engine yesterday morning, before the weather turned nasty here in the NE. Initial impressions and thoughts are as follows:

First off, WOW. This is definitely viable for Pattern. As smooth a runner as the Webra 160 I believe. Lots of useful power in the rpm range we need

The rubber isolation mount described here-in works as well as I expected. Eventhough it is lightweight, it held up fine. To be certain, I need another couple hours of running to make the full assessment, but after 3 runs, everything is a GO. Very little vibration was noticed at all throttle settings, and even without a nose ring, the prop showed practically no sideways movement or wobble. I may forgo adding a ring to the nose.... but, we'll see!!

Engine turned out to be easy to start once I figured out what I was doing wrong. Even with the engine brand new and not broken in, throttleability is better than the Webra and appears to be on par with the YS engines I have run. Idle is superb and with this soft mount, very controlled in terms of vibration. Very smooth transition with a full, throaty sound at full revs. There is very little noise at idle and mid rpms.... I can imagine a model in downwind leg at partial throttle sounding very stealthy. At full revs, the engine makes some noise and I need to figure out how to reduce that. Intake seems to make much of that noise so that should be straight forward to control.

Some of the particulars of the set-up:

The Pipe I used is the large ES carbon pipe intended for the Webra 160. It isn't the one Ed Skorepa makes specifically for this engine. I don't think there will be a need to buy the new pipe, unless he does something totally different for gas compared to fuel for his pipes. Gasoline exhaust gets a little hotter and gasoline has different solvent characteristics than alcohol, so the epoxy he uses might be different, but I don't know that right now. I'll tell you this... the pipe cooled down very quickly after runs were finished; quicker than the header and aluminum header extension I used. The ally header extension is a simple 8" length from a broom handle, attached with silicone rubber at both ends. Silicone rubber and gasoline don't mix as well as silicone and fuel do, but for now, it will do. Ideally, a longer header will be welded to avoid some of the problem

I set the first reflector baffle at 27" from the exhaust flange, straight line (didn't follow the curve of the header) to the fiirst baffle. The prop is the ZDZ 20x10 for initial runs. I also have a 20-12 on hand. Talking with Dean Pappas about it last night at dinner, he suggested for Pattern type speed something like a 19x14. Even with the 20x10, the full revs noise level was similar to that my Webra 160 makes but I didn't measure it. RPMs at full throttle sounded like 7K, maybe 7.2K. That's very useful if not a bit noisy with a 20" diameter
prop. More pitch and smaller diameter will reduce the prop noise a bit.

The battery I used is a 2 cell Li-Ion that I had laying around from an old camera. It's a 2000mah, 8.4 volt set-up (at full charge).

The spark sensor was set at the factory setting and worked well there.

The Walbro carb was set at the factory pretty much. I needed to adjust the low speed needle and just barely touched the hi speed needle. The final settings after running the engine were low speed open 1 1/2 turns and hi speed open 1 1/16 turn. Low speed needle was leaned out about 1/4 turn and hi speed richened about 1/16th. I could see just a bit of smoke. For flying, the factory settings could probably work fine.

An interesting aside regards to flying a gassie like this one, these beasties do not smoke like the standard fuel powerplants do, especially the YS 160-170 engines. Some top level competitors who are flying YS have expressed concern about the smoke trail. Well, this could be an answer to that issue. We'll see how things develop.

I will post some pictures in the next post

MattK

MTK

Here are some snaps of the running beastie

MTK

And a couple more. The aluminum stand-offs are a standard item from McMasterCarr. They are 3/8"x 1 1/2" hex style, with 8-32 threads in both ends. I intend to turn these down some to further reduce weight. They add more than 1 1/4 ounces (about 36 grams) to the mount and I am certain I can get the weight to about 20 grams. Even at the current weight, the mount is not exactly heavy (3.8 ozs). The standoffs cost about $1.40 each...but there are shipping charges as well. I believe that 1/2" square maple stock would work fine in a soft set-up like this, and that would save an ounce probably

MHester

My Feedback: (1)

Looks good Matt!

-M

F.Imbriaco

My Feedback: (56)

Hi Matt,

Congratulations on what appears to be a very viable powerplant option. While the rest of us at our flying field ( especially me) drop big bucks on fuel or Lipo power packs, you will literally be flying on the cheap- even if crude swings past $100 per barrel. I know from our past conversations that fuel economy isn't your primary impetus here, but appears as though you've also conquered N&V issues ,too...And the weight ain't bad , either.

I'm anxious to witness this in your new mount ... so hurry it up and get it done !

Frank

MTK

Thanks Frank, will do....

I wanted to get this done before the snow flies so I can set the firewall in the new design. I'll be working on it with greater purpose now. Still, don't expect to have the new model ready til later in the summer.

Matt

NJRCFLYER2

My Feedback: (42)

Very cool Matt! Nice to hear it's performing well. You will definitely like the way a gas engine responds for hundreds of flights in a row without changing a thing in between. Re. the exhaust trail, most likely you won't see a thing. On rare occasions, with 32:1 oil and a rich setting you can see exhaust from a gas engine, but go with a 100:1 synthetic and it will be invisible if set right.

nonstoprc

My Feedback: (90)

Nice work. I am sure it serves the purpose and is light!

Some questions though.

1. what is the noise level? similar to YS160 with a pipe?
2. any vibration observed on the test-stand?
3. how many layers of rubbers used? By looking at a hyde mount, I notice there is a trace of dried glue covering the join lines between the rubber and the disk. Do not know if that is CA or not.

Again, I have to say it is a great achievement.

MTK

Thanks, but the point is that the mount is straight forward for anyone with some building skill to make. I think the photos should be self explanatory, but if something needs explaining, ask me and maybe I can help.

Well, I don't know what noise level the YS makes. Most guys flying them at the Nats, make the noise requirement. I recall only one pilot failing the test a few years ago at the Team Selection contest. One can set the YS up differently and either pass or fail depending on the set-up...94 dB at 3 meters. On the other hand, there was one notable noise failure of an electric also at this year's Nats F3A Final. The electric's failure was particularly strange because the noise was not objectionable by any standard...much of it was prop noise.

Vibration at idle is about the same as other 2 stroke set-ups we use in pattern. Less than 4 strokes. It goes through a node at around 3000 rpm, as Dick Hanson found out already and reported on same. Mine does the same thing but the soft mount really checks (controls) the vibration amplitude change. At full revs, vibration is almost nil. I grabbed the cylinder to feel the amount of shake and there was very little. Grabbed the stand to feel the amount transmitted and there was practically none. I purposely set the stand on an old flimsy ladder to evaluate and simulate how the set-up would work in a model's fuse, rather than building some strong, heavy, shock absorbing stand that could give me false indications

CA holds extremely well... that's what I use. Medium and thin is all that's needed. The bond between the well cleaned rubber and the plywood is rubber tearing strong. I don't know if that's what Merle Hyde uses in his mounts. I have never owned one of his and I couldn't tell you. Copying his design was easy enough with some information I found on Bob Pastorello's site and have used and refined the techniques over the past 5 or 6 years.

MattK

nonstoprc

My Feedback: (90)

OK.

To save weight further, do you think some alternative material such as CF, kevlar, or fiberglass could be used for the disks?

Does it make sense to use auto-tire rubber to get extra strength? From the pictures, it seems like the rubber is used only on the outside of the ring, not inside. Is that right? I originally thought it should be on both sides so that the engine can be isolated from the frame entirely.

My ZDZ40 was hard mounted and the noise is very BAD. The nose ring probably will be one of my winter projects.

Thanks again.

byoung466

My Feedback: (16)

I made of few of those mounts and found the hardest part stretching the rubber around the disks. I had a tight fit for the rubber ring to the ply rings, curious how tight your rubber is onto the disk. I wound up making a fixture to stretch the rubber open and put the disks inside. Those are a cheap mount to build, the CA was the most expensive part as I recall.

nonstoprc

My Feedback: (90)

Got you.

If the rubber ring is made first, would there be overlapping of the rubber?

MTK

NonstopRC, just a short discussion on rubber technology.... kinda FYI sorta thing:

Rubber stock used in inner tubes is typically nitrile rubber. Tensile strength is around 800-1000 psi depending on the fillers used. There is no reinforcement in the rubber; it's used raw and vulcanized normally with steam. Typically, soap and stearate solution is used as mold release and this stuff must be scrubbed off if one wants to bond the rubber. As I explained in earlier posts, I use alcohol (91% IPA from Wal Mart) for this task. Acetone or MEK or denatured alcohol will also work, but mineral spirits and other nonpolar solvents should be avoided. Soaps and stearates are polar materials and go into solution far more readily in polar solvents and then are easily removed. I apologize for the chemistry lesson

Butyl rubber and even neoprene could be used in inner tube stock. It doesn't matter whether the inner tube is intended for a bicycle tire, lawn tractor motorcycle or car. The rubber stock is the same. Thickness is the deciding factor regards to strength.
For standard mounts for up to 120 engines, 2 layers or 1/32" thick stock is plenty.
For 140-180 size, I use 2 layers of slightly thicker stock, but 1/32" tripled up works very well also but is just a bit too stiff. Too much rubber.
For this 40cc application I went just a bit thicker yet, to 1.1 mm (around .044"). Two layers are used also, on outside of the rings only. First layer as I showed in the photos, is layed down between the ring edges and the second over the edges.

I bought an inner tube from the local motorcycle shop....it cost around 11 bucks and I have enough stock to last awhile. Send me a selfaddressed stamped envelope and I'll send you some material to make your own mount. Just make sure you put enough postage....or, better yet, go to your local shop and buy an inner tube. The diameter needs to be around 85-90% of the final diameter you want. Do not over stretchthe rubber...it makes the mount too stiff. If you have to struggle with the rubber to install it on the rings, the diameter is too small. Overstretched rubber will tend to fail quicker also so avoid it

Other material besides plywood can be used...just got to make sure that CA adheres properly to the plastic or composite.

On the other hand, plywood is readily available, simple to shape correctly with common tools and adheres easily with CA. I know all about composite materials and have considered using such reinforcements on the plywood, but don't. I have found that just aircraft grade ply works just fine. Thin CA penetrates the wood fibers and forms something like a phenolic medium. If you study the photos, most of the plywood has been removed for weight savings. The remaining ring is very strong from it's natural hoop strength.

If you made or purchased one of these mounts you will find a drastic noise difference. I know that some fellows have purchased from Hyde directly. I would guess it cost around 200$...that's why my recommendation is to learn the techniques yourself. It's easy actually.

MattK

nonstoprc

My Feedback: (90)

Matt,

Thanks for the clarfication. It certainly helps.

I also sent you a PM.

MTK

With so much discussion and opinions flying on the ZDZ 40 F3A engine, set-up, and care and feeding, it might serve a purpose to resurrect this thread.

I am not finished with my model but have installed the firewall in it to accept the ZDZ. If I remember, I'll try to post some pics

MattK

kochj

Fantastic thread......
Gives me new hope....

I may be a total idiot right now but my brain is on shut down mode ....

1. how many rings are on this 1st picture??? ply, balsa, then the aircraft plywood rings???
could you explain what is goin on?[sm=spinnyeyes.gif]

2. Probly asked already...... Are any of the wood balsa rings glued together???? OR to any side of the mount?? rear, front ????

Thank you......

Justin

nonstoprc

My Feedback: (90)

Justin,

My understanding of a Hyde soft mount is that the rubber ring goes outside the two rings and the balsa rings are never touched. In fact some rubber should be glued to either inner side of the two rings for protection.

In my commercial Hyde Soft mount for YS110, there seems a thin rubber layer between the two rings. Since this mount does not require nose-ring, the middle rubber probably provides the extra stiffness. This is just my guess.

MTK

Justin,

The first photo shows lamination of the front piece of plywood face....1/8" + 1/16" to form 3/16" thick circle. I simply didn't have 3/16" aircraft ply on hand.

The back ply face remains as 1/8" thick stock

The balsa spacer is several rings of 3/32" balsa with vertical grain. They are first formed and then epoxied together with a layer of 2 oz glass cloth between the layers. Forming is simple....wet the balsa and set it over a roll of tape, wrap it tightly with an ACE bandage and let it dry like that. Then come back and epoxy the assembly together.

Once the two ply faces are built and the balsa spacer is built, the whole thing is epoxied as shown in the second photo.

Once the glue cures, place magic marker alignment marks on the wood and cut the balsa spacer in the middle with a band saw. This cut will form a front section and a back section. It is these two section that the rubber separates and isolates from one another. That's what gives the mount its isolation capability. The balsa in the middle with then have to be sanded flat to allow the two surfaces rotational freedom.

Then proceed with attaching the blind nuts and bolts to the front face and drill the mounting through holes to both front and back plates. If your actual engine mounting is different, adapt whatever you need to the front face. For example, on other mounts for engines with mounting lugs, I epoxy maple bearers to the front face

Now, on to how the doughnut is attached to the firewall. Remember to drill the back only enough to accommodate the mounting bolt you intend to use. You will need to relieve the front face and balsa space as needed to accommodate the head of the bolt you intend to use. You must start small and then relieve as required otherwise the doughnut will not be secured to the firewall.

hopefully the instructions are clear. If not, we'll discuss them until they are

MattK

cmoulder

Matt, as you know from the Syssa 180 discussion I will soon be making one of these mounts. Smaller diameter and only 3 stand-offs, so I am assuming the dimensions will be scaled down a bit. What is the outside diameter that you came up with for your Syssa 30cc engine mount, and what is the width of the balsa spacer rings (compared with the 0.60" for the ZDZ 40 spacer rings)?

I have read through this thread about a dozen times and think I understand the process, but I have a couple of questions for clarification:

I did not read (or perhaps I missed) earlier in your thread the step about cutting the ply rings with a band saw and then sanding smooth. What is done to the sanded balsa faces to make them durable?... hardened with thin CA, or epoxy, or some other covering?

Regarding the rubber bands... Okay, is this correct?... There are 2 - one somewhat narrower one that fits into the recess between the front and back ply plates, and then another that overlaps the ply plates (actually this one is obvious).

Also, not mentioned specifically but it seems obvious that one must be careful to line up the holes carefully for the firewall access bolts.

Thanks very much. I will post photos of my progress in the next couple of weeks. I don't have a well-equipped shop but I have viable work-arounds for accurate execution of all the steps.

More questions to follow, I'm sure!!

cmoulder

OK, looking back at the photos in Post #28 there seems to be some sort of material between the balsa spacer halves, so a clarification of that would be welcome.

Some engineering observations: 1) the wider the donut and rubber rings, the "softer" the mount will be, allowing more amplitude for engine vibration for a given rubber thickness... 2) the larger the mount diameter the less cantilevering perpendicular to the engine's crankshaft axis, therefore less likely the need for a nose ring (which I would really like to avoid!).

Sorry I'm a little disjointed here but I like to get some reasonably close dimensions and "assemble" it in my head before getting started.