Wheel alignment

[Vev]

How do you do a wheel alignment on the main landing gear?

 

Cheers

 

Vev

 

 

[MarcK]

It's just like the old bmx put the wheel between your knees and twist the handle bars. Easy

 

 

[djpacro]

Not sure about your type but straight boards clamped to brake discs and pencil lines on hangar floor works for mine to check toe-in/out. Camber too?

 

 

[Old Koreelah]

I loaded up the aircraft with average TO weight to allow for undercarriage dynamics. Placed long straight edge on the outside of each wheel, lined up with a point on a distant hill to ascertain toe-out.

 

 

[planesmaker]

Long straight edge chocked up to centre height of wheels across the front of tyres and a builders square on outside edge of tyre. Simple really.

 

 

[metalman]

How do you do a wheel alignment on the main landing gear?Cheers

 

Vev

Working out what's wrong is half the job , aircraft spruce sell wedge shaped shims to adjust the alignment

Matty

 

 

[planesmaker]

Working out what's wrong is half the job , aircraft spruce sell wedge shaped shims to adjust the alignmentMatty

I didn't know that Matty interesting to know. However depends on how wheels are attached, my storch I had to weld up holes and redrill, one wheel was toed in a long way. Tom

 

 

[facthunter]

What style of U/C is it Vev and how is the stub attached? Nev

 

 

[turboplanner]

Long straight edge chocked up to centre height of wheels across the front of tyres and a builders square on outside edge of tyre. Simple really.

This method is very practical, but if the undercarriage legs are out of true the wheels will be pointing off the runway together.

 

To add to this method, I would suggest to plumb bob down from the spinner, plumb bob down from the centre of the fuselage at the tail.

 

Mark the line on concrete.

 

Set the long straight edge against the front of the tyres, plumb bob down each end of the straight edge and draw the cross line.

 

If the plumb bob is at 90 degrees, the axis of the wheels is true, then follow planesmaker's simple procedure.

 

It would also pay, while the aircraft is sitting there to measure out from the centre line to a datum point on each wheel (maybe a short straight edge on the outside of the tyres) to make sure the undercarriage or wheel spacers are not making the wheel centres different on each side from the fuselage centreline.

 

 

[Bruce Robbins]

Using a centre line check is good but measuring from the spinner doesn't work due to most aircraft having engine thrust line offset.

 

 

[Russ]

My j160 2mains lean way out, outer 1/3rd of tyres only used, spoke to jab, they sell wedges, I,m about to order 2. ( have renewed tyres & tubes, need to set her up right )

 

 

[Guest Andys@coffs]

My j160 2mains lean way out, outer 1/3rd of tyres only used, spoke to jab, they sell wedges, I,m about to order 2. ( have renewed tyres & tubes, need to set her up right )

<Russ to Jab>....Um seems my Jab is bow legged!

 

<Jab to Russ> Yeah we designed it that way!

 

<Russ to Jab>.....Why?

 

<Jab to Russ> We had a bunch of wedge shaped fibreglass that we had no idea what to do with!

 

<Russ to Jab> Doesn't that sort of infer that the design was faulty?

 

<Jab to Russ> Hell no, our wedges fit just fine!...That'll be $2k per wedge......

 

<Russ to Jab> $2k per wedge!!!!!!!!!

 

<Jab to Russ> Yeah well its aircraft...Its small production runs and the R&D involved in getting it designed to need the wedge cost heaps!

 

 

[Russ]

Pissin me self laughing here, I,m going for a beer.

 

 

[turboplanner]

Using a centre line check is good but measuring from the spinner doesn't work due to most aircraft having engine thrust line offset.

Good point, what's the alternative?

 

 

[ruffasguts]

My j160 2mains lean way out, outer 1/3rd of tyres only used, spoke to jab, they sell wedges, I,m about to order 2. ( have renewed tyres & tubes, need to set her up right )

jabiru fit washers to get axle aligned the assemble with resin and flock

Mick W

 

 

[planesmaker]

This method is very practical, but if the undercarriage legs are out of true the wheels will be pointing off the runway together.To add to this method, I would suggest to plumb bob down from the spinner, plumb bob down from the centre of the fuselage at the tail.

 

Mark the line on concrete.

 

Set the long straight edge against the front of the tyres, plumb bob down each end of the straight edge and draw the cross line.

 

If the plumb bob is at 90 degrees, the axis of the wheels is true, then follow planesmaker's simple procedure.

 

It would also pay, while the aircraft is sitting there to measure out from the centre line to a datum point on each wheel (maybe a short straight edge on the outside of the tyres) to make sure the undercarriage or wheel spacers are not making the wheel centres different on each side from the fuselage centreline.

Yes but........if both wheels are square with each other it is a good start. If a little offline to fuselage I doubt you would notice it when landing. If it is more than a little offline then you then you will probably see it looking at it. However if your measuring it then a simple centreline will check it. Plumb bob wing leading edges against cabin then halfway between points will give a good centreline to tail plumb bob. That way engine offset has no bearing :) Tom

 

 

[metalman]

good thing it's not a taildragger cause then we'd have 185 replies arguing whether it's better to have toe out or toe in,,,,

 

 

[pudestcon]

Good point, what's the alternative?

Centre of the firewall - drop your plumb bob

Pud

 

 

[Vev]

What style of U/C is it Vev and how is the stub attached? Nev

Hi Nev,

 

It's a jab160 U/C

 

Cheers

 

Vev

 

 

[facthunter]

Only seen it done with wedges and reworking the bottom of the leg. Not a lot of help. Nev

 

 

[ruffasguts]

Hi Nev,It's a jab160 U/C

 

Cheers

 

Vev

the jabiru maintenance manual tells all

Mick W

 

 

[Dafydd Llewellyn]

<Russ to Jab>....Um seems my Jab is bow legged!<Jab to Russ> Yeah we designed it that way!

<Russ to Jab>.....Why?

 

<Jab to Russ> We had a bunch of wedge shaped fibreglass that we had no idea what to do with!

 

<Russ to Jab> Doesn't that sort of infer that the design was faulty?

 

<Jab to Russ> Hell no, our wedges fit just fine!...That'll be $2k per wedge......

 

<Russ to Jab> $2k per wedge!!!!!!!!!

 

<Jab to Russ> Yeah well its aircraft...Its small production runs and the R&D involved in getting it designed to need the wedge cost heaps!

Shame to spoil a good yarn, but . . . On spring-leg undercarriages, the wheels are normally set so they lean outwards at the top considerably, when the aircraft is unladen. They lean inwards at full landing impact, sometimes sufficiently to put the edge of the brake disc in contact with the ground. So they need to start, leaning outwards, or you'd get bent brake discs more often. This is a natural consequence of "minimum weight" design of spring legs. If you want to have your wheels upright in normal taxiing, buy an aircraft with telescopic-type or trailing-arm undercarriage legs, and put up with the extra weight and cost.

 

 

[M61A1]

My j160 2mains lean way out, outer 1/3rd of tyres only used, spoke to jab, they sell wedges, I,m about to order 2. ( have renewed tyres & tubes, need to set her up right )

Is the main gear fitted off a heavier model Jab? I have seen a 160 fitted with 230 gear (I think), it had significant camber.

 

 

[Vev]

the jabiru maintenance manual tells allMick W

Hi Mick,

 

That was the forst place I looked but couldn't find what I was looking for … may be I'm looking in the wrong place?

 

Cheers

 

Vev

 

 

[ruffasguts]

Hi Mick,That was the forst place I looked but couldn't find what I was looking for … may be I'm looking in the wrong place?

 

Cheers

 

Vev

jtm001-2 section 6.19 look for manual on Jabiru website

have modified several aircraft to eliminate tyre wear I fitted machine shims and set camber almost vertical with full fuel aircraft operating off hard surface and now do not have to rotate tyres every 100hrs to promote even wear