Dynamic balance of 912 Rotax

[skippydiesel]

True ! I have some in the freezer. best place to store it specially after opening. get much longer usable time / less wastage but it helps to let it warm up for 20 plus minutes.

[Paul davenport]

Mine lives in the fridge. I used to buy it in tube about tooth paste size more expensive in the long run but easier to carry and less wastage when it does go off. You don’t use much on a job . I think last time it went off I repaired a cattle trough with it.

[facthunter]

Mistake it for toothpaste and you will lose fat fast, quietly and without complaint.. Nev

[Blueadventures]

Update for info; Today I fitted the new combined bracket that mounts the optical and accelerator sensors over the centre line of the gear box drive shaft; also just used a 10 mm wide reflective strip. Did two runs (first with out weight and one with the weight plus another two verification of reading run ups) and have the result of 0.07 IPS. This required 6 grams of weight. I used '3M' double sided tape to fix inside the spinner backplate. I'll fly with this and do another balance session later on, I'm sure I'll get it to a lesser reading with practice at determining the weight required. I believe that the calculation for determining the weight needs a little getting used to. ( The formula I'm using is hp divided by 10 plus 30 then multiplied by the magnitude. At 5,000 rpm a Rotax 100hp is developing 68.3hp so I use that now in the math. Next time I do it I'll play around with a variety of weights at the location determined and see how that goes. To date done 6 sessions and made two new brackets so want to get some flying in and see how the '3M' tape holds up (I put torque seal on it so will see if movement develops and I check before and after flights. Thanks for the info from Mark and Paul and sharing this for anyone else doing the same. After the next adjustment I'll refit the balance master so should be very sweet then. Cheers

 

Edited May 3, 2020 by Blueadventures

[Kyle Communications]

Thats a really exception result....You dont usually see that low a figure it should be smooth as silk

[skippydiesel]

Hi Blueadventur - great work & photos. I am very interested in your estimated cost to get to this point. Please advise.

[Blueadventures]

Thats a really exception result....You dont usually see that low a figure it should be smooth as silk

Hi Mark Can notice the difference. Feels totally firm, Hard to describe. I'm rapt. Took 6 sessions. I'll help with the owners 915 in a few weeks and see how it is. He has done a balance on it once so far. Cheers.

[Blueadventures]

Hi Blueadventur - great work & photos. I am very interested in your estimated cost to get to this point. Please advise.

Hi Skippy Takes less than an hour yesterday and today. I have been learning the relationship between where the accelerator sensor is mounted and the angle from 0 above to where it is bolted. For example the top thread post on the port side of gearbox. Had me tricked the early sessions as the weight required position wasn't working. Crunching the figures and results at home indicated the angle (relative to end elevation view) needed to be considered when determining the required degrees that the weight needed to be either removed or added. I just need to do a few more to arrive at a formula to determine the weight required. I'll get it in then next 2 or 3 balance sessions. All done in my own time.

[skippydiesel]

Hi Skippy Takes less than an hour yesterday and today. I have been learning the relationship between where the accelerator sensor is mounted and the angle from 0 above to where it is bolted. For example the top thread post on the port side of gearbox. Had me tricked the early sessions as the weight required position wasn't working. Crunching the figures and results at home indicated the angle (relative to end elevation view) needed to be considered when determining the required degrees that the weight needed to be either removed or added. I just need to do a few more to arrive at a formula to determine the weight required. I'll get it in then next 2 or 3 balance sessions. All done in my own time.

Yeah! I do 99% of my own "mechanicing" too but equipment and material still have to be purchased - I was asking more about $$$$ expended ??

[FlyBoy1960]

I would be extremely worried about buffeting in your bracket.

 

As soon as you rev the engine against the flat surface of your plate you are going to create all sorts of vibrations and harmonics based on the fact that it is just a flat plate with a huge vacuum behind once you start the airflow.

 

Also I can't tell if the bracket is only held in place with two bolts or you are using four bolts ?

 

I would be whacking some big pieces of angle up the back of your plate to try and reduce the harmonics, also maybe make the plate thinner at the top (less wide is what I mean) because the optical sensor does not need to be mounted as strongly as the vibration sensor

[FlyBoy1960]

Also, you need to put heat shrink on the end of your fire sleeves because at the moment if you get a leak fuel will wick up the inside of your fire sleeve and make it next to useless. 99% of the aircraft I have seen have some sort of heat shrink on the end of the fire sleeve or they have safety when at around three or four times to create a good seal. Some people use both, safety wire and then heat shrink over the top to cover the ends. If you need to ever take the tube off then you only need to at worst cut away the heat shrink

[Blueadventures]

Also, you need to put heat shrink on the end of your fire sleeves because at the moment if you get a leak fuel will wick up the inside of your fire sleeve and make it next to useless. 99% of the aircraft I have seen have some sort of heat shrink on the end of the fire sleeve or they have safety when at around three or four times to create a good seal. Some people use both, safety wire and then heat shrink over the top to cover the ends. If you need to ever take the tube off then you only need to at worst cut away the heat shrink

Thanks for comment. I'm putting heats rink on ends soon. The safety wire first sounds a good method. Thanks.

[Blueadventures]

I would be extremely worried about buffeting in your bracket.

 

As soon as you rev the engine against the flat surface of your plate you are going to create all sorts of vibrations and harmonics based on the fact that it is just a flat plate with a huge vacuum behind once you start the airflow.

 

Also I can't tell if the bracket is only held in place with two bolts or you are using four bolts ?

 

I would be whacking some big pieces of angle up the back of your plate to try and reduce the harmonics, also maybe make the plate thinner at the top (less wide is what I mean) because the optical sensor does not need to be mounted as strongly as the vibration sensor

Agree, these brackets have been a work in progress. Hadn't thought of trimming the profile. Will do that. Also next version of bracket will have the optic sensor done lower and beside the accelerator sensor as only counts rpm and the accelerator sensor will remain over the gear shafts center line. Just doing a bit of r&d and myth busting, etc. Learning about this kit and it sure makes a noticable difference. Cheers

[skippydiesel]

I would be extremely worried about buffeting in your bracket.

 

As soon as you rev the engine against the flat surface of your plate you are going to create all sorts of vibrations and harmonics based on the fact that it is just a flat plate with a huge vacuum behind once you start the airflow.

 

Also I can't tell if the bracket is only held in place with two bolts or you are using four bolts ?

 

I would be whacking some big pieces of angle up the back of your plate to try and reduce the harmonics, also maybe make the plate thinner at the top (less wide is what I mean) because the optical sensor does not need to be mounted as strongly as the vibration sensor

 

Only experience/ a test would prove/disprove your concern. The plate looks to be substantial (4mm ?) and is very well secured although it looks like even more fixings are possible.

[FlyBoy1960]

It would be easy to test, mount your accelerometer probe horizontally on the plate in the same axis as your strobe sensor. Then run the engine and it would tell you how much buffeting you are getting in the horizontal plane instead of the vertical plane

[Blueadventures]

Also, you need to put heat shrink on the end of your fire sleeves because at the moment if you get a leak fuel will wick up the inside of your fire sleeve and make it next to useless. 99% of the aircraft I have seen have some sort of heat shrink on the end of the fire sleeve or they have safety when at around three or four times to create a good seal. Some people use both, safety wire and then heat shrink over the top to cover the ends. If you need to ever take the tube off then you only need to at worst cut away the heat shrink

Replaced the oil hose with the recent engine service and fuel hoses are next and put silicone tape on ends.

[FlyBoy1960]

the silicon tape is probably more needed on the fuel lines which in your photos have not been completed

[Blueadventures]

the silicon tape is probably more needed on the fuel lines which in your photos have not been completed

Agree next job, just seeing how it wraps on.

[waraton]

Has anyone used one of these to balance their prop? There is fluid in them with an explanation at the link below. Are they available in Australia?

 

http://www.balancemasters.com/how-it-works.html

[Blueadventures]

Has anyone used one of these to balance their prop? There is fluid in them with an explanation at the link below. Are they available in Australia?

 

[ATTACH type=full" alt="1600513320157.png]56441[/ATTACH]

http://www.balancemasters.com/how-it-works.html

I had one on and noticed improvement. Took it off at present as a mate loaned me his dynavibe unit and the balance is close to perfect. And the engine feels great. I’m keeping the balance master as I will put it back on after next time I do a dynamic balance. Worth getting and fitting.

[Kyle Communications]

Dan3111 on the forum here is the agent for them..send him a message

[skippydiesel]

I had one on and noticed improvement. Took it off at present as a mate loaned me his dynavibe unit and the balance is close to perfect. And the engine feels great. I’m keeping the balance master as I will put it back on after next time I do a dynamic balance. Worth getting and fitting.

 

Just an idea - I agree 110% with you static & dynamic balance of your propeller. I would suggest tat you replace your "Balance Master" - if you happen to get a chip out of one blade,the prop will go out of balance, perhaps severely. The Balance Master may just get you home without shaking your aircraft and its components .

[Blueadventures]

Just an idea - I agree 110% with you static & dynamic balance of your propeller. I would suggest tat you replace your "Balance Master" - if you happen to get a chip out of one blade,the prop will go out of balance, perhaps severely. The Balance Master may just get you home without shaking your aircraft and its components .

Will be in about 2 1/2 months time unless I get some spare time in between. Just need to arrange the dynavibe when I'm ready to do it; as I will re run the readings as the prop is and then fit the balance master and repeat the reading. This will show the benifit / performance result - static. However it's our good diving period as well and we can catch Barramundi up until 1 November; and other fish so when the weather is right I'll be diving in the blue water rather than flying in the blue sky so much. Just finished the annual and engine service (takes time out of flying) and will do the fuel lines soon as they're due. As the prop is all good further work can wait.

[skippydiesel]

My limited understanding of the Balance Master (BM) is that it works to correct out of balance propellers - if your prop has been well static/dynamically balanced you are unlikely ti see any benefit from the BM. That is until your prop goes out of balance.