Savannah main undercarriage attachment

[IBob]

The main undercarriage is held in place by a steel plates underneath, secured by SS bolts  to front and rear of the leg.

I recently saw pics from a heavy landing where the UC had folded back under the fuselage. The steel plates have slotted holes, and the front bolts were intact but had pulled entirely through the plates.

On examining my steel plates, I found they are now dished upwards, probably due to over heavy braking. A factory build on the airfield has 3 penny washers under the plate to prevent this, so it is not a unique problem, and I have now added washers to mine.

 

 

 

 

Edited June 9 by IBob

[facthunter]

Wouldn't a hard rubber limit stop do it better? Most other suspensions have one.   Nev

[IBob]

Facthunter, this is the main UC.  It is clamped between hard rubber (lurethane?) over and under it. That is the red stuff in the pic.

But hard braking or the like causes the wheels to pull back, and all that load is taken by the front mounting bolts.

Edited June 9 by IBob

[facthunter]

 I see said the blind man. Thanks.. Brakes that work well.  Not Clevelands are they?   Nev

[skippydiesel]

Hi IBob,

 

Speculation:

• Would not a made to measure rectangular steel plate, say 4-5 mm thick, spread the load better than a stack of washers??
• You could also consider hard rubber (or metal) spacer, back bolt shaft, between fuselage & retaining plate, to limit the pivoting action.

 

[IBob]

Skippy, that bottom plate has raised edges , to hold in place the bottom rubber under the UC. So a flat plate wouldn't do it.
I think the source of the problem is the holes in the plate, they are slotted in the fore and aft direction, so weakening the plate and allowing it to dish up, as you can see in the pic. I guess they are slotted to allow for variations in the bolt positions, but I think the slotting is excessive. And it could have been done only for the rear bolt, which does not take the braking load.
As it is I'm confident that the washers will prevent the bolts pulling through....not very elegant, but I want to be flying rather than tinkering.

Oh, and I'll be less heavy footed with the brakes in future.......)

Facthunter, the brakes come with the kit, and I suspect are made inhouse. The boys with the really fat wheels put bigger brakes on, and sometimes add a wire stay from firewall back to the lower UC to prevent the UC folding back under.

[skippydiesel]

42 minutes ago, IBob said:

Skippy, that bottom plate has raised edges , to hold in place the bottom rubber under the UC. So a flat plate wouldn't do it.

 

I was thinking replace the washers with a 4mm rectangular plate. Would cover a larger area and likly be as good/better than the washers as a spacer/load distributer.

I think the source of the problem is the holes in the plate, they are slotted in the fore and aft direction, so weakening the plate and allowing it to dish up, as you can see in the pic. I guess they are slotted to allow for variations in the bolt positions, but I think the slotting is excessive.

 

The slotting may be to allow pivoting movement

 

As mentioned earlier - You could also consider hard rubber (or metal) spacer, on the back bolt shaft, between fuselage & retaining plate, to limit the pivoting action example below

42 minutes ago, IBob said:

 

 

[facthunter]

ALL those types of U/C have trouble with the amount leverage of the Brake force on the U/C leg. .. It's part of the  deal. They are made to fly in the air. Nev

[BC0979]

I agree on the excessive slot width for the bolt size. 

Truly appreciate the heads up on this potential issue