Eagler's Nest
Engines => 2 Cylinder => 1/2 vw => Topic started by: mikeheckler on October 17, 2019, 06:58:08 AM
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Hi,, I have a Hummelbird with a 1/2 vw scott castler 37 hp engine with 160 hours on it. In early summer it quit at 2,000 ft between Lyons N.Y and Sodus Bay. I was able to make a successful landing in a corn field without any damage to the airplane. When I got the Hummelbird back to the hangar and remover the cowl part of the crankshaft and connecting rod had gone through the case. I tore the engine down and found the crankshaft was broken into 3 pieces, 2 fractures right at where the counterweights were welded on to the crankshaft. I called Scott Castler about it and he said mine was the only 37 hp engine that he knew of where the crankshaft broke, however there were many 45 hp engines with the cast crank that have broken, he offered to sell me a new FORGED crank and case at his cost. I accepted the offer understanding that the new crank would be Forged, not cast like the original.
After receiving the parts I put the engine back together and have about 50 hrs on it, but it vibrates as bad as the old one. I had the prop dynamically balanced, but the vibration is still bad.
I saw an earlier post where the question was asked, How many IPS is acceptable with this engine when a dynamic balance is preformed, but there was no answer, .
I also saw a link to an Ipad app for vibration and ordered it and mounted the Iphone to the instrument panel with Velcro or just pressed it against the instrument panel when I was flying.
My results on the x and y axis between 3,000 and 3,500 rpm has been in the 1.7 to 2 g range.
I would be interested in finding out if any one else has used the app to get a relative indication of vibration so we all could compare what is dangerous and what is not,,,Thanks a lot Mike Heckler,, N607SN
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What app exactly are you using - I noticed more than one in the app store. I would be willing to run it against my 1/2 VW and compare results. It will be a few days before I can do so as currently out of town but I am also interested in the results.
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It is just called Vibration
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Vibration by diffraction Limited Design LLC
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Great post! I hope to dynamically balance my prop this weekend so I'll let you know if it happens. Currently @ 3200-3500 I cannot read the gauges because it shakes so much. Can you tell me where and how much weight you currently have on your hub? Glad you made it down safely.
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Glad you are interested a lot of people are not.
Looking from the front of the engine toward the back the weight is 90 degrees to the left of the top dead center line on the prop hub when the hub is at tdc,, in other words at the 9 oclock posisition when the tdc alignment mark is at 12 oclock, looking front to back.
I don't know what the weight weighs.
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Are you talking about the bob weight put on the back of the prop hub with the mass balance job done on the crank..?
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Yes it came with the crank
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Ok, next question... Is it the bob weight off the old crank or did it come with the new crank..?
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With the new crank
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(https://media.giphy.com/media/181OUQHOCfde0/giphy.gif)
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OK, next question... Was the prop statically balanced before it was dynamically balanced..?
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Yes it was
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(https://ci3.googleusercontent.com/proxy/5cH665fmsHnO7jgznr0JoXmVLeQp8yuk3WtB-hQWLT4a80msGQ7P_jsAdTHKkmdaeFBUMu3zsSlEdIp2Zygm7yzzJ7TkULCUNWZoHg=s0-d-e1-ft#https://media.giphy.com/media/26BGqofNXjxluwX0k/giphy.gif)
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How many IPS is acceptable with this engine when a dynamic balance check is preformed, does anyone know?
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How many IPS is acceptable with this engine when a dynamic balance check is preformed, does anyone know?
I don't know the answer to your question, but if you are sure the bob weight is where it is supposed to be and the crankshaft journals were drilled hollow and the prop tracks within 1/16th inch then you may want to try a Balance Masters (http://www.balancemasters.com/aircraft.html)...
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Also leave your wooden prop sitting horizontal, else if it is vertical moisture can migrate to the bottom blade and throw it out of balance.
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Forgot to mention, a couple months ago had a dynamic prop balance done, initially 3.5" and then added washers to spinner and got it down to 1.5" I could not feel any difference
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The dynamic balance was done and a week after that I installed a balance master, and it is still on, there is less vibration with it on than with it off. The vibration is still bad though..
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Mike,
I found this on the 1/2 vw group... apparently he changed props to get different rpms. Was not able to find the Dynavibe 1/2 vw case study.
Bob Wood
Oct 17 6:00 AM
Yes, the biggest issue I had was a rougher power setting around 2800 rpm. I flew with the dynavibe attached and documented the power bands so I could avoid them. The needles in the Mikuni vm26’s must have been hopping around. I would get a bogging in this band and it was not fun. That all went away when I got below .5. If the prop tracking is not dead on it will not work. I changed props to get there.
Sent from my iPhone
Show message history
In both axis?
On Oct 16, 2019, at 11:33 PM, Bob Wood rwood@... (rwood@...) [HalfVw_Engines] <HalfVw_Engines@yahoogroups.com (HalfVw_Engines@yahoogroups.com)> wrote:
I was able to get .42 with a perfectly balanced prop. Took some time but well worth it
Sent from my iPhone
On Oct 16, 2019, at 9:18 PM, Pete peterz@... (peterz@...) [HalfVw_Engines] <HalfVw_Engines@yahoogroups.com (HalfVw_Engines@yahoogroups.com)> wrote:
Use it always on mine, but its nog possible to get better/lower than 0.6IPS in both the vertical (rotational) and the horizontal (rocking couple), as they are competing.
On Oct 16, 2019, at 9:29 PM, Bob Wood rwood@... (rwood@...) [HalfVw_Engines] <HalfVw_Engines@yahoogroups.com (HalfVw_Engines@yahoogroups.com)> wrote:
DynaVibe dynamic balancing works very well. See their on line 1/2 vw case study
Sent from my iPhone
On Oct 16, 2019, at 7:33 PM, Pete peterz@... (peterz@...) [HalfVw_Engines] <HalfVw_Engines@yahoogroups.com (HalfVw_Engines@yahoogroups.com)> wrote:
Not possible to balance out the rocking couple of the offset two cyl.
On Oct 16, 2019, at 6:29 PM, John Hartgerink johnhartgerink@... (johnhartgerink@...) [HalfVw_Engines] <HalfVw_Engines@yahoogroups.com (HalfVw_Engines@yahoogroups.com)> wrote:
You can get very good balance on a 1/2 VW but you need to take it to a
Performance Machine Shop that can do high speed balances by adding
heavy metal to the crankshaft counterweights. V8 race engines are balanced
this way and are none as neutral balanced engines.
Jan
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Well we tried to balance the prop today however as we went up on power the software told us to shut down vibration was "dangerously high", to that effect. We managed to get a reading @1500 at about .46 ips. I believe somewhere below <.07ips is acceptable for GA. Next step, we are going to make a 8" disk or spinner back to with holes every 30deg to give us more flexibility when adding or splitting weight. More to follow. . .
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Interesting,, let me know how it goes!
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Jeopardy
cat. LSA & 103 class aircraft
No blue pill needed for this engine...
What is VW Type 4?
(flywheel drive of course)
Peace.
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Type 4 was used in several models. (https://www.vwheritage.com/blog/2017/07/13/type-4-engine-explained/) By the time they quit making them they came with 2000 CC stock.
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good link
the Bosch CIS injection is hard to find mechanics that will work on 'em. Most will convert back to carbs. No emission tests for the old vanagons and buses
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Well we tried to balance the prop today however as we went up on power the software told us to shut down vibration was "dangerously high", to that effect. We managed to get a reading @1500 at about .46 ips. I believe somewhere below <.07ips is acceptable for GA. Next step, we are going to make a 8" disk or spinner back to with holes every 30deg to give us more flexibility when adding or splitting weight. More to follow. . .
Take a look at the balancing methods in the attach pdf.
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FWIW, this is the chart that's in the Aces prop balancer manual.
Rusty