When and how to re-bend the Savannah main spring?

[Hasse]

Dear friends,

 

Has anyone removed and re-bent the Savannah main spring? If so, how did you do it?

 

According to ICP this may be done twice without affecting the spring strength significantlly.

 

I can't remember having done any really hard landings but either my memory is going bad(mad) or the main spring is too soft for my hands. Still, there are a lot of talk about the front wheel suspension but I couldn't find any threads in this forum where people have complained about the main spring. Anyway, rumour says that ICP has a new and stronger version of the main spring./Hans

 

 

[Kyle Communications]

They do spread if you load them too much. Hard landings at MTOW will spread them. One of the locals here has re bent his a couple of times. It is done with a press. You can make one from angle iron and a hydraulic jack. Or get a 20 tonne press and lengthen it to suit the width of the U/C

 

 

[Hasse]

Thanks Kyle,

 

You wouldn't happen to know what angle I should aim at? I assume around 10 degrees.

 

 

[IBob]

Thanks Kyle,You wouldn't happen to know what angle I should aim at? I assume around 10 degrees.

Hi Hasse. I do not know anything about bending, or whether the Savannah U/C has changed.

 

Here is a pic and sketch of my unused Savannah S U/C. Kit Dec 2014. Soon to be used (cheesy grin).

 

Happy landings!

 

 

 

 

[Hasse]

Hi Hasse. I do not know anything about bending, or whether the Savannah U/C has changed.Here is a pic and sketch of my unused Savannah S U/C. Kit Dec 2014. Soon to be used (cheesy grin).

Happy landings!

Thanks IBob,

The picture and your drawing are great help when bending the main spring to the original angles. I hope you will be flying soon./Hasse

 

 

[Piet Louw]

Thanks IBob,The picture and your drawing are great help when bending the main spring to the original angles. I hope you will be flying soon./Hasse

Hi Hasse. I am attaching a template I got from John Waterson of Savannah South Africa. Hope it helps.

 

 

[Hasse]

 

Hi Hasse. I am attaching a template I got from John Waterson of Savannah South Africa. Hope it helps.

Hi Hasse. I am attaching a template I got from John Waterson of Savannah South Africa. Hope it helps.

Thanks you all for your help! However, I am not going to re-bend the main spring after all . When I tried to remove the spring I happened to place a jack on the spring in the centre under the U/C and lifted the aircraft in order to support it later with some trestles. Anyway, this pressure on the spring seemed to do the trick because the angles now seems completly ok with both weels pointing outwards as they did before. Apparently the spring has some kind of flex-point which should not be exceed but if this happens (within some limits I suppose) may be restored just by applying pressure in the centre and push it back. Does that make any sense?

If this doesn't work, I will let you know/Hasse

 

 

[IBob]

I have no experience of this, but I am surprised that just lifting the aircraft in that way would restore the spring. Although if you lift the aircraft then put it down quietly, the wheels will probably sit a bit differently until they are rolled?

 

Maybe sit 2 people in and jump around a bit, then see how it looks?

 

 

[facthunter]

If it can be bent and straightened easily it is too soft. The only remedy for that is to have it hardened and retempered. There are plenty of spring works around that do it all the time. Set it in the final shape first. Nev

 

 

[Hasse]

If it can be bent and straightened easily it is too soft. The only remedy for that is to have it hardened and retempered. There are plenty of spring works around that do it all the time. Set it in the final shape first. Nev

Yes, well that's also what I thought. I found it quite soft. On the other hand, shouldn't all Savannah main springs have the same hardness? Anyway, I will see what happens after a couple of normal landings./Hasse

 

 

[facthunter]

You never know what someone else has had done to it. A lot of shops take it to temper temperature and reset it. If they overdo it it's like yours is. TOO soft and too easily bent. You can hardness test it easy enough. Nev

 

 

[Kyle Communications]

I hope you realise that if you are pushing the aircraft around on the ground you will see the wheels splaying out but once you take the weight off it then the wheels go back to where they were. This happens on mine when I take it in and out of the hangar. All I do is go to each wing tip and lift the aircraft from the main spar to the trailing edge and lift it so the wheel then goes back to where it will naturally go with the metal tension then do the other wing and the wheels then have that inward tilt. Its just the weight of the aircraft torsioning the UC leg frame. Give it a try and you will see wht I mean...sort of what you have done with the jack

 

 

[Hasse]

I hope you realise that if you are pushing the aircraft around on the ground you will see the wheels splaying out but once you take the weight off it then the wheels go back to where they were. This happens on mine when I take it in and out of the hangar. All I do is go to each wing tip and lift the aircraft from the main spar to the trailing edge and lift it so the wheel then goes back to where it will naturally go with the metal tension then do the other wing and the wheels then have that inward tilt. Its just the weight of the aircraft torsioning the UC leg frame. Give it a try and you will see wht I mean...sort of what you have done with the jack

Hi Mark,

You are absolutely right. That's also what I found. I jumped inside and taxied around for a minute and after that both wheels pointed outwards. At present I always fly at MTOW (with two sand bags as a passenger) for testing reasons and that extra weight may also add, I suppose. Anyway, it's good to know that the main spring is probably not destroyed, only a bit too soft, in my opinion.

 

Thanks all for your help - this is a great forum for discussion and support./Hasse

 

 

[1Phils]

Hi Hasse, I bent my main spring in the middle with a press and took it over centre until the axels are slightly pointing down so when the plane is sitting on the wheels they are sitting straight up and down not splayed out.

 

Phil.

 

 

[Hasse]

Hi Hasse, I bent my main spring in the middle with a press and took it over centre until the axels are slightly pointing down so when the plane is sitting on the wheels they are sitting straight up and down not splayed out.Phil.

Hi 1Phils,

Ok, so did it keep its attitude or became it softer after the bending?/Hasse

 

 

[IBob]

Hi Mark,You are absolutely right. That's also what I found. I jumped inside and taxied around for a minute and after that both wheels pointed outwards. At present I always fly at MTOW (with two sand bags as a passenger) for testing reasons and that extra weight may also add, I suppose. Anyway, it's good to know that the main spring is probably not destroyed, only a bit too soft, in my opinion.

Thanks all for your help - this is a great forum for discussion and support./Hasse

Hi Hasse,

Just a thought: While your sandbags will replicate the weight of a passenger, they will not replicate the weight of a passenger under impact (eg heavy landings): a body has a lot of give or bounce, while sand bags will behave pretty much like blocks of concrete. So the energy at moment of impact will be a lot greater. Can you not find...erm...someone bouncy???........)

 

 

[Hasse]

Hi Hasse,Just a thought: While your sandbags will replicate the weight of a passenger, they will not replicate the weight of a passenger under impact (eg heavy landings): a body has a lot of give or bounce, while sand bags will behave pretty much like blocks of concrete. So the energy at moment of impact will be a lot greater. Can you not find...erm...someone bouncy???........)

Hi Mark,

Hmm, I see what you mean. Problem is that during flight testing (has to bee 50 hours to complete the personal flight manual - Swedish rules for experimentals) nobody can join me. So for another of 30 hours or so it will be only me, a couple of sandbags and the GoPro on board.

 

Also, now it's autumn which means lousy flight weather until Winter. So I have to wait a bit longer with the final testing. I asume it's the oppposite in Australia./Hasse

 

 

[1Phils]

Hi Hasse, The spring has held its shape for over 12 months so far. I don't think that the metal is soft you just reset it back into the unrested shape..

 

Phil.