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Old Feb 19, 2012, 11:59 PM
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D-Rock's Avatar
Phoenix, AZ
Joined Oct 2004
1,911 Posts
Hi BIW, sorry to hear you are having all the issues with the plastic spinner, and from what you have described you have been very meticulous with your efforts. The spinner I am using now is the second plastic one- the first broke in a nose over. While there is a slight vibration, not nearly as much as you mentioned and without the distortion. It almost sounds like perhaps the prop is out of balance?

When I first flew the prototype, I used an aluminum spinner from http://tysplanes.com/home and it worked well. I looked at his site and couldn't find where he was still selling them but you might want to try contacting him and see if he could still get them.

Let me know if can assist any further.

D-Rock
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Old Feb 20, 2012, 08:15 AM
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BuildItWright's Avatar
Melbourne, Australia
Joined Jul 2008
909 Posts
Spinner talk continued....

Hi D-Rock,

Thanks for the reply, I'm going to try running the prop and spinner by themselves to see if I can isolate the gremlin that causing me so much grief.

I ran the motor again tonight during daylight so that I could get a tacho reading, the vibration set in at about 4800 rpm on the V2 spinner, I was getting around 6000rpm on the V1 spinner that has the warped backplate!

Do you know what rpm's/current your flying your G with? At 6K there was a lot of thrust, probably enough to get it into the air I think.

I'm pretty sure I emailed Typlanes about the spinners a few months ago and he told me that he no longer stocked them.

If I can't get the home made spinner working the premade options I've identfied are:

CMP Pro 145mm plastic spinne
r, available from http://ak-models.com/mm5/merchant.mv...Category_Code=

Meister Scale 6.5" aluminium spinner for $55 plus postage
http://www.meister-scale.com/ME109/A...cessories.html

David Platt 5.5" plastic spinner with aluminium backplate for $75 including postage

Fliteskin also have a nice
148mm aluminium spinner for $99 plus postage!
http://www.fliteskin.com/Me109page.htm

BIW.
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Old Feb 22, 2012, 08:03 AM
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BuildItWright's Avatar
Melbourne, Australia
Joined Jul 2008
909 Posts
I've done some more tests on the spinner and prop.

First I took the spinner and backplate off and bolted the 16x8 prop on alone. It ran up to full throttle without any vibration at all. I didn't have the eMeter attached for this run so I don't have the motor stats.

Next I put the spinner backplate on along with the prop, it had a little more vibration but still managed about 900 watts before the vibration set in.
I noticed that the spinner backplate is not running true either according to the datum line I maked the other day. I might try shiming the backplate with some paper/cardboard to see if I can get it running smoother.

I'm going to see if I can find a piece of 5-6mm thick aluminium so that I can try making a stronger/truer backplate as well. I'll ask around at my club to see if I can fine someone with a lathe to turn it out for me.

BIW.
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Old Feb 22, 2012, 08:51 AM
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Martin Irvine's Avatar
Canada, ON, Kingston
Joined Aug 2000
2,035 Posts
Years ago I had a similar vibration problem with a smaller model with an innrunner that wasn't solved until the rear of the motor was supported. This was despite a number of different spinners including a TruTurn.

You have a light, vacu-formed spinner which will help a lot, but I have to wonder if you wouldn't better off with a FRONT mounted motor. Rear mounted outrunners are standard now, but think about the spinning mass in front of the firewall. The "firewall" needs to be very stiff as the power increases, and the mounting bolts on a wide footprint. Then, everything spinning should be in perfect balance. (Note that the firewall needs to be securely tied into the rest of the fuselage)

If you go with a front mounted motor, then you have the mass of the spinning motor behind a solid bulkhead, and the spinner and prop in front. You don't have to be an engineer to see that this is a better balance of spinning masses.

It will be a pain to change, but I think that will be the solution.

Martin
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Old Feb 22, 2012, 02:13 PM
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Doug Bartley's Avatar
Canada, ON, Owen Sound
Joined Oct 2008
2,872 Posts
I've run into similar problems. If the back plate isn't 100% true, it will never be truly vibrationless. I've remachined a couple now, finding out out the machined mating surface didn't match the backplate face. Even a .001" wobble at the plate would make a large spinner like yours have .020" wobble at it point.
On one spinner the backplate was warped, on the other, the centre of the backplate was not perfectly flat. removing about .005" sqaured the faces.
After squaring, the spinner ran fine at 10,500rpm!
You may also want to check the collets mounting face (or prop adapter). I've found them out quite frequently by as much as .005", more than enough to tilt the backplate, again causing the same issues. FWIW Doug B
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Old Feb 22, 2012, 08:52 PM
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BuildItWright's Avatar
Melbourne, Australia
Joined Jul 2008
909 Posts
Front mount?

Quote:
Originally Posted by Martin Irvine View Post
Years ago I had a similar vibration problem with a smaller model with an innrunner that wasn't solved until the rear of the motor was supported. This was despite a number of different spinners including a TruTurn.

You have a light, vacu-formed spinner which will help a lot, but I have to wonder if you wouldn't better off with a FRONT mounted motor. Rear mounted outrunners are standard now, but think about the spinning mass in front of the firewall. The "firewall" needs to be very stiff as the power increases, and the mounting bolts on a wide footprint. Then, everything spinning should be in perfect balance. (Note that the firewall needs to be securely tied into the rest of the fuselage)

If you go with a front mounted motor, then you have the mass of the spinning motor behind a solid bulkhead, and the spinner and prop in front. You don't have to be an engineer to see that this is a better balance of spinning masses.

It will be a pain to change, but I think that will be the solution.

Martin
Thanks for the advice Martin/Doug,
Another friend of mine had suggested front mounting the motor, but I already had the fuselage built and didn't wan't to think about it. It looks like I may have too! Even with my firewall reinforcements the motor is still flexing 2-3 mm under high RPM with the out of balance spinner which is unacceptable.

Looking at the nose of the 109, I think it would be possible to remove the stringers on top of the motor to give me internal access to the nose ring. Then it would be relativly easy to epoxy a plywood front mountinside the nose ring. the nose mount could then be braced back to the original firewall with some extra ply. This would make it very strong and hopefully reduce the vibration problems.

BIW.
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Old Feb 25, 2012, 05:27 AM
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BuildItWright's Avatar
Melbourne, Australia
Joined Jul 2008
909 Posts
Front mounting the Eflite 60

Today I made a start on converting the motor from being a rear mount to a front mount. I'm using better quality 4mm 5 ply wood instead of the soft 3mm 3 ply that was supplied with the kit. I'm going to use two 4mm laminations so that the motor will be supported by 8mm of ply. The plan is to add braces from the new motor mount back to the original firewall as well. This should stop all the flex thats happening at the moment.

BIW
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Old Feb 26, 2012, 08:06 AM
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BuildItWright's Avatar
Melbourne, Australia
Joined Jul 2008
909 Posts
Motor mount cont.

Tonight I have made some more progress with the new motor mount. I've cut out the doubler and sanded it so that its a snug fit in the nose of the 109.
My Dremel has earn't it keep this week!

I was a bit concerned that the motor was going to get build into the nose with no way of removing it for repairs. As it has worked out there is no need to worry as I had to enlarge the hole in the original firewall to give me enough clearance to fit the motor mount in position. This will allow me to slide the motor back so that I can get a screw driver in to remove the X plate before sliding it back under the battery tray for removal(this will have to be cut to remove the motor).

I'm a little concerned about the lack of cooling for the motor with the front mount in postion, but there aren't too many options for adding any either.

BIW.
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Old Feb 26, 2012, 10:01 AM
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D-Rock's Avatar
Phoenix, AZ
Joined Oct 2004
1,911 Posts
Nice job on the conversion BIW. As for cooling, I am not sure there is any airflow over the motor from the front with the standard motor position due to the spinner. Most of the cooling comes from the small scoops from the side. Hope this mounting helps to eliminate the vibration issues. .

D-Rock
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Old Feb 29, 2012, 08:38 AM
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BuildItWright's Avatar
Melbourne, Australia
Joined Jul 2008
909 Posts
Tonight the new motor mount and it associated bracing was glued into position.
It all went pretty smoothly and I didn't make too much of a mess with the epoxy.

While I was gluing the side braces in position I had an idea to help cool the motor. I'm going to drill a hole(at lease 10mm in diameter) in each side of the motor brace then make up ducts that will direct air from the nose scoops onto the front of the motor, this should keep the motor reasonably cool.

BIW.

Effort since my last post, 03:00, total build time is 94:00
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Old Feb 29, 2012, 08:52 AM
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Modelholic's Avatar
Perth WA
Joined Feb 2007
1,041 Posts
Very nicely done.
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Old Mar 01, 2012, 08:39 AM
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BuildItWright's Avatar
Melbourne, Australia
Joined Jul 2008
909 Posts
Progress

I added the cooling ducts to the airframe tonight. Once they were done I had to answer the question, had the new front mount reduced the vibration?
This had to be answered before I called it a night so I grabbed the Tx and Emeter and plugged everything up. Previously I couldn't get above about 250 watts before the vibration threatend to tear things apart. This time I got to 700w before I noticed any vibration, it wasn't too bad so I thought what the heck and gave it full throttle. 990 watts at 50 Amps showed up on the Emeter , there is a bit of vibration but I think it is acceptable at this stage. I'll try rebalancing the spinner again to see if I can get it any better.

A question for D-Rock, what sort of throttle settings do you typically use during flight? I don't think anywhere near full throttle will be neccessary to fly this bird.

BIW.


Effort since my last post, 01:30, total build time is 95:30
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Old Mar 01, 2012, 09:39 AM
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D-Rock's Avatar
Phoenix, AZ
Joined Oct 2004
1,911 Posts
Hi BIW, I usually cruse around 3/4 throttle- not a speed demon but that was not the goal . I usually use full throttle for maneuvers and occasionally on take off. However, the take off run is about 10-12 feet. I have been planning on trying different props to see if I get any additional speed..

D-Rock
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Old Mar 01, 2012, 11:53 PM
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BuildItWright's Avatar
Melbourne, Australia
Joined Jul 2008
909 Posts
I agree totally D-Rock, I'll be very happy to have the 109 flying a scale speed. Too many scale models fly faster than scale spoiling the whole effect, either due to their high wingloadings/being overpowered I'm guessing.

1/5 of 300mph is 60mph or 100 km/h so this is about what I'm aiming for.

BIW.

PS. I'm not sure about trying different props, if you up the pitch you will have to drop the diameter, thus more prop will be lost behind the big spinner.
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Old Mar 02, 2012, 03:58 PM
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Ojimy's Avatar
Cincinnati, OH
Joined Mar 2003
311 Posts
This "imbalance" you're talking about that affects your model at different RPM's sounds a lot like "resonance." Strictly-speaking, an "imbalance" should evidence itself anytime the rotating mass is set into motion, and become gradually more intense as RPM increases. The fact that you're saying that the vibration "sets in" at certain RPM threshold but is not apparent at lower values makes me wonder if a very slight imbalance isn't finding a sympathetic dance partner in a very light, "springy" airframe?

If the problem IS resonance, stiffening up the engine mount and surrounding structure may make the problem disappear, or at least raise it beyond any RPM your motor/prop combo is capable of generating.

Just a thought from an interested passerby. I love this stick-and-former Micko stuff and you're doing a great job on yours. I just wish I had the space to tackle one myself...
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