Outer Limits 4x4 Board

I just got to thinking that MAYBE if you could oil and spring them up and get enough travel a cheap alternitive to air shocks could be motocross forks off a 600 or bigger bike

gtwebbie wrote:I just got to thinking that MAYBE if you could oil and spring them up and get enough travel a cheap alternitive to air shocks could be motocross forks off a 600 or bigger bike

where would you get springs to suit the weight?

You can get motorcross forks resprung with various springs rates and the valving can all be changed on some forks, lots of ability to modify for the right set up. Front forks would give you heaps more travel, but might find it very hard on fork seals if flexing it up all the time (depends on the forks too tho.)

So then thats a types off yes then???????????

you'll never no if you don't try.

In theory yes, I have ssen it done. H/D springs can be purchased but the biggest problem is flex in the shaft on extension, this then causes seal wear and other more major issues.

Even in a bike when rading off road, forks can flex a lot. For low speed crawking they could work..... but coilovers would be more reliable.

Jaosn

beretta wrote:You can get motorcross forks resprung with various springs rates and the valving can all be changed on some forks, lots of ability to modify for the right set up. Front forks would give you heaps more travel, but might find it very hard on fork seals if flexing it up all the time (depends on the forks too tho.)

but going from a 90kg bike to a 1000kg buggy is a little different.
Not sayin it cant be done, saying it wouldnt be worth the effort...

but on a bike the shocks are locating the wheel where as on a buggy the link set up will be locating the wheel and the shocks will only be taking the weight. Look at a normal shock there rod is tiny, because they are not locating the wheel (like the front forks of a motor bike).
If u can set it up to take the weight i see no reason why it would not work.

interesting thread.... I might give it a go in the rear of the rangie for shits n giggles

a fork design would not work, being a " Y " shape if attached at three locations it would bind the suspension movement.

Making an adaptor to mount as a single mount each end like a normal shock would probably cost more than just buying air shocks and being done with it.

I like the idea

I used to ride motocross like alot of other people on here too. And the front forks are constantly bottoming out and dropping all the way, so i don't see that being a problem when flexing them up on a rig. Of course there's going to be alot more weight/pressure on them...

When a bike's ride height is set it may only have the front shocks compressed 10% of their travel or so. Where as buggy's are setup quite the opposite. So with HD springs in them I don't think it would be very hard to set them up on a buggy. The shocks setup on a buggy with alot more compression in them then designed for, could kill the spring life though

sierrajim wrote:a fork design would not work, being a " Y " shape if attached at three locations it would bind the suspension movement.

Making an adaptor to mount as a single mount each end like a normal shock would probably cost more than just buying air shocks and being done with it.

A single fork leg is not "Y" shaped. Each motocross fork leg is bolted to the front hub, then clamped at the bottom of the steering tube (like where the headset is on a mountan bike) and then again at the top of the steering tube (close to where the handlebars are mounted).

wouldnt be a problem in bolting them up at all.

see attatched pic of a downhill MTB with forks designed by an ex motocrosser....ignore the brace between each lower leg as these dont exist on motos

ok so who wants to donate me a pair of front forks of a big arse bike

sierrajim wrote:a fork design would not work, being a " Y " shape if attached at three locations it would bind the suspension movement.

Making an adaptor to mount as a single mount each end like a normal shock would probably cost more than just buying air shocks and being done with it.

What do you mean by "y" shape?

I don't think it would be worth while doing really either. But if you already had a couple pairs of spare forks left over and felt like a tinker it would be interesting

i think you'll find it ends up costing more to adapt them than what it would just cost to buy air shocks. remember that they are going to need a lot more freedom in the mounts than they do on a bike. so you are up for rod ends or spherical bearings, plus machining to adapt and mount them to the shock bodies/shafts. then you need your custom rate springs as well.

could work with some cantilever arms

N*A*M wrote:could work with some cantilever arms

What NAM said. But thinking about it (cos works boring today!), you would probably come out of it worse $$ wise if you did it properly, better off going for something built for the job, like fox shox.. If you do go ahead, get some Ohlins forks, or at least 48mm forks off a KTM.

When I mentioned popping fork seals I was referring to the difference in weight on the forks for a buggy and the fact that they would probably spend a lot more time at full compression than they would normally on a bike, albeit not a violently on a buggy. My KTM had 48mm front forks, revalved for racing and aftermarket springs, if I really flogged phuck out of the bike in an enduro and bottomed out the front forks enough, it would blow seals (or if someone else tied the bike down without my wheel choc in it would blow em out too!)

I reckon it'd be an ok idea if the buggy was really really light!! I realise linkages would be locating the wheel but the overall weight difference would be large! ie a YZF R1 forks have about 150mm of travel, the bike weighs about 200kg dripping wet, and can carry a rider/pillion weight of about 200kg, so therefore if you did a stoppy with a pillion each fork leg would have about 200kg of weight on it, so one on each wheel of a buggy and it'd have to be not much more than 800kg (I realise you can put heavier springs in but im thinking fork seal durability) Even then youd only have 150mm of travel per wheel, a cantilever setup could increase the travel but would put more weight on the shocks.
KTM forks have about twice the travel of the roadbike forks and youd have to assume that if the fork seals on the roady can handle 200kgs then the ktm ones could as well my ktm has 43mm WPs (2000) and the newer ones (03 on) are 48s and have 3 bushes instead of 2.

All in all it depends how heavy the buggy is - you could run 2 forks per corner if you wanted? Also fyi for KTM forks a 0.44kg/mm spring is fairly heavy, 100kg rider, fairly quick - mine are lighter than this cos im not that quick...

Interesting idea though....

It was done in NZ on a trials truck several years ago, from memory 2 forks per wheel on a very light buggy, not sure if they were air as well
It was not a top truck but it was competitive
J Top

N*A*M wrote:could work with some cantilever arms

wheres that donater BMW GS?

What about using two rear motorcross shocks per side instead?

By the time you spent the money to buy a pair of MX Shox (even second hand ones), then spend money to get them rebuilt, heavier spring, different valving, new seals, Modify the mounting system you could have searched around and gotten out of easier and cheaper by buying a set of Fox Air shox.

If you did do the Bike thing whose to say that even after spending all that Money that they will even work. Then what have you got?

POS wrote:By the time you spent the money to buy a pair of MX Shox (even second hand ones), then spend money to get them rebuilt, heavier spring, different valving, new seals, Modify the mounting system you could have searched around and gotten out of easier and cheaper by buying a set of Fox Air shox.

If you did do the Bike thing whose to say that even after spending all that Money that they will even work. Then what have you got?

a very interesting story and empty wallet. much worse things to spend dough on!

POS wrote:By the time you spent the money to buy a pair of MX Shox (even second hand ones), then spend money to get them rebuilt, heavier spring, different valving, new seals, Modify the mounting system you could have searched around and gotten out of easier and cheaper by buying a set of Fox Air shox.

If you did do the Bike thing whose to say that even after spending all that Money that they will even work. Then what have you got?

i totally agee there pos . we looked at doin this when i built trev , i went out to find the longest shocks possable , the best i could find were only 10'' of total travel i gave up there and went and got some foxshox . for the inner coils for a set off custom forks are not cheap . got a price for a dude for some heavyer coils for a tt 600 and they came in around $450 mark ,thats just the coils he still had to re sleve and do seals to bring them up to new . my 2 cents

The longest forks I know of are the marzocchi super monster T (12") - mountainbike shocks but about as strong as MX shocks. But is would be cheaper to buy 4 proper buggy airshocks than 2-pairs of forks, and you will have more travel with the airshocks.

AAARRRRE but I got everyone's grey matter working and I am always looking outside the SQUARE so thanks. Ideas are what keeps our sport evolving.

gtwebbie wrote:AAARRRRE but I got everyone's grey matter working and I am always looking outside the SQUARE so thanks. Ideas are what keeps our sport evolving.

Do you think it will be able to drive through the first layer of gravity

ISUZUROVER wrote:The longest forks I know of are the marzocchi super monster T (12") - mountainbike shocks but about as strong as MX shocks. But is would be cheaper to buy 4 proper buggy airshocks than 2-pairs of forks, and you will have more travel with the airshocks.

You can get Marzocchi 50mm odd forks with 12"+ travel, or white power 50mm forks with 12"+ travel second hand for around $500 per pair of forks

I also now of a buggy with a Showa honda rear shock set up on all corners, no linkage if I remeber, so it is a 1:1 ratio, as apposed to most bikes that operate on a lever system. It worked exceptionally well but the vehicle was built for NZ's race to the Sky, it was 4wd power buy a 1200cc Suzuki bike engine so was very light. http://www.racetothesky.com/

Steve Riley (Driver/owner) came second in 2002, only beaten by Possum Bourne in is Subaru. and third in 2003.

Jason

would work perfect for a kids buggy im thinking...hhrrrmm...another project