Tipsy Nipper

If any is interested in a new set of aluminium wheel door his/her nipper, I am currently making a few sets, because we can't get the right tires..
If your are interested in a set of wheels.
Let me know.

Hi All,

I guess this is to get away from the 4.95 x 3 1/2 tyres which are nearly unobtainable. I have been quoted £400.00 each for old/new stock. Maybe the price reflects the fact that this old size is a Hawker Hurricane tailwheel and anybody who can afford to operate a Hurricane can probably afford the cost!

I've got modification papers in with the LAA for a hub to accept the common 400 x 4 tyre. If anybody is interested there is a useful feature, If the hub through bolts locations are drilled for a Rohloff bike disc then they can be used instead of the awful Nipper ones which distort. At 160mm diameter they will operate with the standard Nipper caliper without any other changes and are readily available. The 4 bolt arrangement of the Rohloff can't be added to the standard Nipper hub as they get too close to the existing Nipper 6 bolt ring. This can be seen on the disc shown which has been drilled with the Nipper attachments as an experiment. Also you can't use the more common bike 6 bolt attachment as they are on a smaller pitch circle and foul the axle set up.

This picture compares my 400 x 4 wheel with the old style 4.95 x 3 1/2



And this shows my wheel assembly parts



I've also gone for completeness with hydraulic bike brakes. An awkwardness with bike brakes is that they are made to fit on the left of the wheel, this means that one side of the aircraft will have the operating cable pointing down and located too close to the ground. The hydraulic units I've used get round this because the connections are banjo fittings and I've rotated them to point conveniently to the undercarriage strut.

The parts to adapt the Nipper caliper torque link for the bike caliper.



and assembled
Note that the heavier caliper is now supported against vertical loads by an extra bolt through the torque link. The two end bolts are standard Nipper.



And to finish
note that the banjo fitting hasn't yet been rotated so points down.



If anybody is interested I have drawings and CAD files for all parts. LAA approval hasn't been completed yet but I don't see any showstoppers. The only machine that had to be used was a hobby lathe for the turning, although I used a hobby mill for some of the other parts because it avoided hacksaw and file labour.

Jim

Just to add, my intentions to build a set of hubs was two fold:
My 'old style' tyres are serviceable but I have no spares and I was concerned that I could get caught out with a damaged tyre away from base. That could become logistically rather tricky to sort out but the 400 x 4 is readily available. Also my standard discs and calipers were unserviceable which drove the rebuild of the brake system.
Secondly I was keen to design and fabricate the hubs (and a Leburg ignition conversion) as an exercise to increase my CAD and machining capability. The processes are quite simple except for the central tube which is about 100mm dia. x 100mm long by 1.5mm thick wall. That took some exercising of the little grey cells!

I didn't check to see if Airweld had any 400 x 4 hubs in stock at the time (about 3 years ago) but I would still probably have made this set. If I was sorting this problem now, just as the aircraft is about to come airborne, I would most likely buy a set, from Martens (or Airweld if they have any), simply to get things moving. An adaptor could be fashioned to fit a Rohloff disc to a Nipper format hub if necessary.

Jim