Anybody recognise this free wheeling hub

[diffwhine]

I wouldn't bother. I've never seen any significant fuel saving when fitted and they have the issue of lack of lubrication to the swivel pins.
If only doing 2000 miles a year, I doubt you will save anything. Save your pocket money for something more useful.

[Alan Drover]

I got rid of mine and reverted to the standard set up but that was my choice. It's really up to the individual. When I had them fitted they were always locked in the fixed position anyway.

[Dormy]

To understand them, think of brake shoes in a brake drum, except that these shoes are small and metallic and are held off the "drum" by little springs.


When the rear wheels are spinning and slipping and 4WD is engaged, the front halfshafts are spinning faster than the disconnected front wheels.

Centrifugal force spins the "shoes" outwards to bind on the "drum" and transmit drive to the wheel.

That is how I understand it, but others may have a better description.

Or another way is to think of the ratchet free-wheel on a bicycle. When you pedal the wheel drives, when you don't it free-wheels - only these lock going backwards too.

Centrifugal force doesn't work them; The rollers sit on a sort of multiple cam inside the hub, which forces them to lock the moment the halfshaft begins to rotate at the speed of the wheel hub. So if stationary, 4x4 is instant and the halfshaft can never spin faster than the wheel.

If you break a rear halfshaft you can simply engage 4x4 and drive on. But the free-wheel will take effect and it becomes a bit like driving an auto-box, with the engine revs falling off when you take your foot off the throttle.

Nor are you left without a handbrake. On an upward slope you can use first gear and a bit of gentle clutch to hold the vehicle and then pull-on the handbrake and the hubs will stay locked. You can do the same facing downhill by using reverse. But this would be an emergency situation only as any significant disturbance of the vehicle i.e. an HGV passing at speed, could move your L/R enough for the hubs to disengage.

These free-wheel hubs appear to have been an optional accessory offered by Martin and Walter, as they seem a fairly common fitment on Dormobiles.

[diffwhine]

If that's the case, they stay...

I'm very familiar with the principle - I've rebuilt quite a few freewheel series one gearboxes.

[Craig T]

Have to say, the biggest advantage of having them on my one is using them as a step to reach further into the bonnet.

If you want to prime the fuel pump or press the start solenoid when the key switch is a being a bit iffy, standing with one foot on them does make it easier to reach in there 

Craig.

[GlenAnderson]

They are the only type of FWH that I would consider fitting to my Land-Rover, mainly because of their design not leaving you stranded in the event of a rear halfshaft failure; something that I have personally experienced in traffic, uphill, with a heavily loaded trailer, which was a significantly traumatic enough experience that I never want to repeat it ever again.

[Calum]

As said they are indeed MAP automatic hubs. I had a set on the Carawagon (which were on when I got it) but I reverted to the manual type after a scary steep descent in the snow. I then sold them on.

They work on a 'trapped roller freewheel' principle, I suppose you could say like a form of sprag clutch. As Diffwhine suggests, it is very similar in principle to the Rover freewheel used in 80" transfer boxes and Rover saloon cars.

The 'central hub' is what I will call the clutch mechanism, which is in two main parts, and the 'hub body' is the bit which is seen from the outside.

The central hub is held stationary by a tab which engages on a special locknut for your hub bearing. I say 'stationary, as the ring which has the tab on it does spin in the central hub but with a reasonable amount of resistance. So as soon as the halfshaft spins, the inner member (cam) of the central hub rotates and with the outer part of the central hub held stationary by the tab. The rollers will climb the cams until they all bear on the inside of the hub body. So long as there is torque applied by the halfshaft the components all stay 'locked' together now, until of course the wheel tries to move faster than the central hub in which case the 'freewheel' aspect of the design takes over. It's hard to describe clearly without diagrams!

The rollers are all held inwards by a garter spring so when the hubs are free there is no touching of the rollers to the hub body, unlike in the freewheel in an 80" where the rollers are all in contact. It's for this reason the hubs need the 'tab' and the special locknut to initiate the contact between roller and main hub body.

Oh and despite the rumours that always surround them, they aren't handed and they do work in both directions. But they do need the special locknut to work (which seem to be missing from 90% of those I see for sale!) and they do unlock on engine braking which is not fun!

[GlenAnderson]

If anyone has a single orphan one sat in a box somewhere that they want to rehome, drop me a line. 😃👍

[Exile]

This thread has had me looking at the auto hubs on my Station Wagon more closely, whilst it is jacked up in the shed.

So, I've discovered that the hub on the RH front wheel rotates freely in both directions, without rotating the half-shaft.


However, the LH front wheel will rotate freely backwards, but it's forward rotation is locked.

I assume it is this LH wheel that is wrong, and that the rollers are stuck/locked against the outer body.

Is this correct, and is there an easy! solution?

[Dormy]

I guess that your L/H hub has some stickiness or corrosion going on.
They are very simple mechanisms which dismantle easily (usually) - Don't be scared of taking yours apart, there is little to go wrong.

As you are seeking advice, I suggest taking apart the one which seems to be working. Then, having familiarised yourself with the parts, how they fit and how they work, look at the L/H one which doesn't seem to be operating quite right.

HTH
Ian

[Exile]

Thank you Dormy.

(I was late to see your reply!)

[GlenAnderson]

I've just finished fitting a pair to my 109". I'm in the process of editing a video on the job. I'll post a link when it's done.

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