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bespoke portal drop boxes/axles


carl hurst

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Anyone think of a solution to the seal problem?

The whole point of the plastic gear and big teeth is the avoidance of the need for seals. Think of it in terms of a tracked vehicle. If it were a plastic wheel runing round a metal track, you wouldn't be worried about seals.

The plastic makes the interface quiet and self lubricating. It will wear - but only like your tyres do. You could have the ring gears water jet cut making them relatively cheap.

I don't see an issue with legality on the road - so long as it looks up to the job.

Si

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If it were a plastic wheel running round a metal track, you wouldn't be worried about seals.

I would!

I really like this idea, but what would happen if a decent sized stone or branch got caught between ring and inner gears? Portals occasionally grenade even within sealed boxes, I'm just not seeing how an open gear is going to work.

I guess for a start it'd be easy enough to seal the outer side of the wheel off - stopping half the carp getting in as well as branches poking right through.

How long would a plastic gear last when its full of mud? How could you attach the plastic gear to the inside of the wheel? Bolt to a flange?

Maybe the best way is to put a 'face' on the outside of the wheel, and run one on the inside that isn't a tight fit - so it just stops the big bits getting into the wheel, but water / liquidy crud can flow in/out? No seal needed, but does most of the work (still reckon the plastic would wear fast though)??? Bit like a brake drum I guess. (i.e constant maintenance and filling with carp!)

I still like it though...

Al.

:)

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Of course if you could seal it, you'd give yourself the opportunity to run CTIS easily AND give the wheel internals positive pressure, helping keep the carp out.

Anyone know if you could make a decent seal around a wheel rim (just inside) that would handle any reasonable road speed?

Al. Thinking.

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The whole point of the plastic gear and big teeth is the avoidance of the need for seals. Think of it in terms of a tracked vehicle. If it were a plastic wheel runing round a metal track, you wouldn't be worried about seals.

The plastic makes the interface quiet and self lubricating. It will wear - but only like your tyres do. You could have the ring gears water jet cut making them relatively cheap.

I don't see an issue with legality on the road - so long as it looks up to the job.

Si

Simon,

You might also like to think along the lines of the geroller internal gearing (as used in some hydraulic motors), in place of conventional sprockets. Also, the tooth forms and rollers used in cyclodrive gear units.

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Of course if you could seal it, you'd give yourself the opportunity to run CTIS easily AND give the wheel internals positive pressure, helping keep the carp out.

Anyone know if you could make a decent seal around a wheel rim (just inside) that would handle any reasonable road speed?

Al. Thinking.

IMHO, the best seals of all are Caterpillar seals - devised by Caterpillar for sealing in areas around the crawler tracks of their dozers.

For road speeds and the rim diameter, the seal lip pressure times velocity will be a problem for seals.

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For road speeds and the rim diameter, the seal lip pressure times velocity will be a problem for seals.

Hmm thats what I thought. If the seal radius from the wheel centre could be reduced, it'd help keep things reasonable, but I can't see a way without interfering with the input shaft (and reducing 'portal height').

How about supporting side loads on the wheel? If you're sliding down a side slope and the wheel meets a fixed object (for example) the torque on the point where the shaft/structure meets the wheel will be pretty nasty... What structure would the thing run on? I'm thinking more and more that a central pivot (fully enclosed within the wheel volume) would be handy.

Al.

:)

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Does it John? Hmmmm. Got any pics?

Time to break out the crayons:

post-139-1207919058_thumb.jpg

Obviously(?) its a cross-section of a wheel & tyre (grey), I put a surface on the outer side of the wheel, inside the rim left of centre is a 'brake rim' - instead of a disc, the blob at the top is the caliper. The axle comes in from the right, through a steering knuckle (purple blob) to drive the pink inner gear which drives the red internal ring gear attached to the wheel.

If you were smart, you could possibly shoehorn the knuckle into the wheel too (or at least some of it) which would give you a cracking scrub radius. :)

No structure is shown. The grey centreline could be have a shaft / bearings to help offset lateral torque loads. It could also give an easy solution for CTIS.

How to mount the wheel? What doe it actually run on? How to seal the insides from mud and crud. Portals can grenade due to portal box flex, so I'm pretty sure this wouldn't last 5 minutes with rocks and carp being forced between the gears.

One issue is that your incrasing your rotating mass considerably, which both sucks and blows.

Al.

:)

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Time to crack out the Technical Lego me thinks!

Two of my favorite vehicles are in front of me built from Lego Technic. A fully working Scammell Contractor and a fully working AEC Matador with pnumatics and working winches. I have about £1200 of the stuff.

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Two of my favorite vehicles are in front of me built from Lego Technic. A fully working Scammell Contractor and a fully working AEC Matador with pnumatics and working winches. I have about £1200 of the stuff.

Night Train, I'm not sure if you frighten me, or I love you. Either way, you have true dedication to the cause.

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The Scammell, twin drive motors, seperate motors for the winch and for the powered shear legs at the back, pnumatics for the crane and the under reach, full front and rear suspension , 6x6 drive. It can lift 2kg on its crane at full reach and climb a vertical wall until it falls over on its under lift. Needs dusting though.

post-6454-1207945336_thumb.jpg

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The Matador. Twin drive motors and motor driven chassis winch with folding crane jib. It can lift 1.7 kg on the crane and 2kg with the ground anchor down. has front suspension only though but can still climb walls until it falls over. It is a copy of the one I used to have on my front drive. the winch can be used ove the jib, out the fairlead rollers at the back or fed round to the front and out under the side of the cab.

post-6454-1207945677_thumb.jpg

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A (almost) exact copy of the Lancashire United Matador used for bus recovery at the Manchester Transport museum. Undriven but has a hand powered chassis winch and a fully working, twin winch Harvey Frost 8 ton crane, suspension and steering. This one was featured with the real thing at an event there a few years ago.

post-6454-1207945925_thumb.jpg

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  • 1 year later...

the whole concept is wrong...

to add drop boxes to a land rover axle is ideal, but the people who use them are likely to give them a lot of pain.

the tinfoil land rover axles really are not up to the job of supporting the extra twist on the axle casing. Also it would make the land rover axle +5(?) inches wider at the least, then you add big wheels your vehicular width is gonna be greatly increased.

maybe creating an entire axle would be easier, because its not that much harder, and it gives you all the possible variables.

Chris.

..and it works:

3688144.jpg

3688148.jpg

Axle overall width is increased by about 6.5" but by chosing wheels with a larger offset the final increase in width is a mere 2".

Lift of the drop box is 4.9" and the boxes are fully interchangeable....

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While the thread has been dormant - I've had another idea as an evolution of the ring-gear.

Imagine making the internal pinion and ring gear with a similar form to a Birfield joint (like a Land Rover CV) such that it not only transmits drive - but also allows an angular offset for steering. I've not run any FEA on the idea to see if it's strong enough - but my gut feeling is good. Then you simply have a steering swivel that has reduction and offset built in. Seals are the biggest issue - but there are certainly big high speed seals out there.

The CV-Boot will act as a diaphram to effectively equalise the pressure on the inside and outside of the joint, minimising the differential pressure the seal must cope with to keep oil inside and mud out.

Si

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