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Front Wheel Modifications

[50 hrs]

November 23, 25 & 29
December 6, 7,  9 & 13

The original front wheel assembly and method of operation is far too harsh for the Australian conditions with most of our strips, apart from the bitumen surfaces, hard gravel and dirt with tufts of grass. After sourcing assemblies from many suppliers, I decided of purchasing an assembly manufactured by Hughes Group of Companies who manufacturer the Lightwing Aircraft as well as boats. The weight of both wheel assemblies is approximately the same, however the 13" front wheel is larger and softer.

The fork has a collar enabling steering through the front wheel. Attached to the collar is two sleeves enabling two welded chrome molley tubes to be attached to the frame of the undercarriage thus giving support to the front wheel assembly to prevent shimming or flutter during taxi, take-off and landing regardless of the surface. A grease nipple provides a lubrication point to allow the fork to move freely inside the collar.
Each leg of the fork has a cylinder with suspension provided by compressing a 1" diameter piece of high density (Sure 80) Polyeurethane. As the swivel arm moves, the piston pushes on the retaining collar compressing the polyeurethane.
The polyeurethane has been compressed to enable an AN4 bolt with spares to be inserted into the holes at the bottom of each fork. The spacer prevents the arms from being squashed too far, restricting the movement of the swivel arm.
Using the original front wheel support tube, another bracket has been constructed to slide into the tube and bolt into place with two AN4 bolts. The bracket provides the 17 degree angle, has a thrust bearing to take the shock and provide the turning moment, and the two push rods will be attached to the turning arm to provide the front wheel steering. The steering assembly is held in place with an AN5 bolt, castle nut and split pin tightened sufficiently to allow free movement.
These two images show the front wheel assembly in its temporary position at an angle of 17 degrees to the vertical. The stem of the wheel will bolt to the mounting bracket that will insert into the engine mount frame. Two AN4 bolts will be used to hold the assembly in position after the correct height has been established by releasing the full weight onto the wheel once support brackets have been welded to the collar and fixed to the cabin frame next to the wing support brackets. 
With the full weight of the engine resting on the front fork bracket, the tube is cut and all bolt holes drill so the horizontal stabilizer is parallel with the ground. The two braces have been shaped and welded into position to prevent the front fork from skimming, as well as providing an anchor point for the steering push rods to be attached.

1" X 1/8" steel has been welded onto each foot pedal rod to enable push rod linkages to be attached to the bracket on the front wheel assembly. The steel arm is passed through a slot in the floor pan to enable the steering push rod to be bolted onto the bracket.
A rubber boot will be shaped out of an inner wheel barrow tube for each push rod and fixed to the floor pan to prevent fumes from entering the cabin.
With the two support tubes keep the wheel at the correct angle while preventing flutter.   A 1" X 1" aluminum frame has been constructed to bolt onto the swivel bracket assembly providing a solid mounting point for the landing light rather than on the engine cowl.
The linkage rods connect the brackets under the pedals to the steering arm on the front wheel. The new landing gear configuration which works extremely well without any shimmy or flutter yet provides enough spring for our hard Australian runways.

December 27, 28 & 30

After the front wheel collapse and the damage to the engine mount frame, a new front wheel support structure has been constructed from 2 sections of 1 1/2" x 1" x 1/8" T6 aluminum angle with 6 lengths of 3/4" x 3/4" x 1/8" T6 aluminum angle stiffeners. Solid rivets have been used throughout its construction and securing to the cabin frame and the base plate. 1/8" round head solid rivets are spaced every 32mm apart to the base plate and 40mm apart to the cabin frame.
In addition, 2 round head 3/16" solid rivets have been used to secure the new support to the corners of the cabin structure and 2 only 3/16" round head rivets either side of centre.
1/8" counter sunk rivets have been used on the front of the front wheel structure so that the firewall will fit flush to the frame and structure.
While this modification will add additional weight, it will provide strength and support for the front wheel which can now be removed without interfering with the engine mounting frame.
A .040" stainless steel plate has been cut and shaped to fit the section cut out of the floor pan that was damaged as the wheel collapsed under the aircraft. The two slots are for the steering linkages and holes predrilled for the foot pedals, the pattern taken before the section was removed.
1/8" round head solid rivets spaced every 32mm are used to secure the stainless steel plate to the aluminum angle, while 1/8" pop rivets every 32mm are used to secure the stainless steel plate to the floor pan.

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