lightweight rock crawler and Hydraulic drive options

[artie on edge]

Sorry if this has been suggested before (I havent had time to read all posts right through) why not move the engine back a little bit and have one longer and one shorter drive shaft to give you room to fit the seat lower?

Depending upon how short you have to go it might give you extreme angles on the UJ's but this will only be momentarily and its not as if the beast is ever going to do 160,000 miles is it?

[fabr]

Those motors are the way to go!!! WHere in hell did you get them? THey ain't cheap.

[artie on edge]

What is a dizzy??  It's something on top the motor?

Dizzy = distributor

[Baloo]

[Baloo]

Sorry if this has been suggested before (I havent had time to read all posts right through) why not move the engine back a little bit and have one longer and one shorter drive shaft to give you room to fit the seat lower?

Depending upon how short you have to go it might give you extreme angles on the UJ's but this will only be momentarily and its not as if the beast is ever going to do 160,000 miles is it?

hi Artie
      but it all fits so nice as it is,  l would need to add to the wheel base really to get the passenger seat in low down, not a problem in itself its just a handy size for getting around tight corners as it is,  l will have a look at stretching it a bit when l next have the bits out on the floor,  but it looks like the hydraulic drive buggy will come first     

[Engineer]

I am waiting to see the hydraulic schematic for how to run four wheels?  Just tee them all together?  If one comes off the ground then what?  Maybe a valve for each wheel that will stop the flow to that wheel?  Kind of like a turning brake for every wheel.  If two are spinning then pull their levers to cut the flow to them and give it to the others?

I have seen the gear equilizers.  It is like a two gear pumps back to back, that guarantees equal flow out of both circuits.  You could use 3, one to split for front and rear, then one at the front and one at the rear to split sides.  I don't know if this method would make it so "tight" that it would bind when trying to steer sharpely, like a locked in truck.  It might be nice to have a little slip between wheel RPM's.

[Baloo]

I am waiting to see the hydraulic schematic for how to run four wheels? 

me too   

theres a few options on how too connect up  and l dont know which is best, to some degree it will depend on the type of steering l decide on,

l think l have decided against fold in the middle like a dumper, pivot steer,
l cant see how l could make a cage that folds in the middle that looks ok.

so that leaves skid steer and conventional like a buggy,

conventional like a buggy has a few downsides in the fabrication and wieght departments,  once the wheel and motor are bolted together then the whole assembly has to turn as one on some pivots probally track rod ends,
 all this has to be made up and fitted on the ends of the trailing arms, then you need steering arms to connect the hubs together but theres no point in just linking the 2 sides together with a conventional  straight bar
as this will ruin the clearance that your have gained from having hub motors in the first place, so an awful lot of track rod ends tube and linkages all add up to more wieght 

so going back to skid steer of sorts,  the machine you mentioned earlier swarther ?  if l understood it right the left and right motors are each fed hyd fluid from a speed/gate valve in equal quantities untill you turn the steering wheel and then one motors supply is reduced and the other increased ?  so adopting that all l have to do is add the front wheel motor to the rear either using a flow divider so as the front and rear on either side get the same amount of fluid or just plumb the front motor in series with the rear by routing the oil coming out of the rear motor straight into the front motor, that way the front and rear would have to be going at the same speed as they are using the same flow ?

do you think it will still turn like a swarther with extra wheel on each side given the wheels are about 85" apart  ?
or would it be better to just fit 2 levers one for the left and one for the right that way l could move the levers opposite directions and turn on the spot like a track vehicle

or as engineer said l could connect all 4 motors of a common supply and then have a valve to shut any one off if its spinning, which is probally the simplest/cheapest,   but  this does limit me to conventional steering though ?

l think l am going to make a test rig and do some experimenting

Andy
 

[Engineer]

do you think it will still turn like a swarther with extra wheel on each side given the wheels are about 85" apart  ?

NO....

IMO that will not work. 

The swather works no problem because the other wheels swivel freely.  A skid steer type loader works because they are almost square.  usually the wheelbase is shorter than the track width.  In any kind of ruts the skid steer will not work, it will just spin tires on one side.

Because with the skid steer you have to drag half of the tires to turn, I think that you will limiting a vehicle that needs every bit of drive possible.  Not to mention the wear and abuse of the frame when dragging it around.

For steering with the trailing arm design, instead of the linkage I would use hydraulics.  One cylinder on each side.  The cylinders need to be the double rod end variety so they don't gain or lose displacement when they move.  I think that they could be run in series to get equal movement.  Change the toe in by bleeding a little oil?

Your idea or running the wheel motors in series is very interesting.  I don't know what the pressure drop would look like across them.  I believe with any series circuit each would see 1/4 the power, however they would have to run the same RPM, so if one was trying to freewheel, it would consume no power or pressure drop, and the next motor would have more power.  It just might work.  Because the motors are bi-directional the back pressure shouldn't hurt anything......  I don't see a case drain in the pictures.....  is there a small third port somewhere?


I agree articulated steering is no good mainly because of the CG issues someone mentioned earlier.

[BDKW1]

I don't think the shafts on those are rated for any kind of radial load. It would be better to build a bearing housing/hub assembly that the motors could be bolted too.

[Engineer]

Or put the motor higher, and chain drive down to a sprocket mounted to the wheel.  The lower sprocket could be bolted to a disk brake hat.  And pick up some power.


Actually if direct drive is dictated by speed and torque, this would be a good applictation for a front bearing off of a 1/2 or 3/4 ton truck.  You would just need an adapter from the hydraulic motor shaft to the CV spline size for the bearing.

[lee1969GB]

Like this.

[Baloo]

Like this.

hi Lee, there you are where you been laterly

yes lookin at your sketch it might end up somthing like that, maybe mount the motor lower down at  3 oclock to keep the c of g lower, l was trying to avoid this route if possible as its least 8 sprokets to be made and 4 chains plus 4 tensioners all add up to more wieght and complication,  quite a bit more maintainence too adjusting the chains and oiling/greasing them,  but if this the way forward then its the way l will go

[lee1969GB]

Baloo, Almost did not bother when I logged in and saw the 2 pm,s about banning me for being naughty    Thats all water under the bridge now, here I am, see how it goes.

Think of it as a strong mudguard (or fender) mount

[Baloo]

Baloo, Almost did not bother when I logged in and saw the 2 pm,s about banning me for being naughty    Thats all water under the bridge now, here I am, see how it goes.

Think of it as a strong mudguard (or fender) mount

what you up to lee to be a bad boy,  must have been before my time as l dident see anything

yes very sturdy wheel arch mount

[Baloo]

NO....

IMO that will not work. 

The swather works no problem because the other wheels swivel freely.  A skid steer type loader works because they are almost square.  usually the wheelbase is shorter than the track width.  In any kind of ruts the skid steer will not work, it will just spin tires on one side.

Because with the skid steer you have to drag half of the tires to turn, I think that you will limiting a vehicle that needs every bit of drive possible.  Not to mention the wear and abuse of the frame when dragging it around.

For steering with the trailing arm design, instead of the linkage I would use hydraulics.  One cylinder on each side.  The cylinders need to be the double rod end variety so they don't gain or lose displacement when they move.  I think that they could be run in series to get equal movement.  Change the toe in by bleeding a little oil?

Your idea or running the wheel motors in series is very interesting.  I don't know what the pressure drop would look like across them.  I believe with any series circuit each would see 1/4 the power, however they would have to run the same RPM, so if one was trying to freewheel, it would consume no power or pressure drop, and the next motor would have more power.  It just might work.  Because the motors are bi-directional the back pressure shouldn't hurt anything......  I don't see a case drain in the pictures.....  is there a small third port somewhere?


I agree articulated steering is no good mainly because of the CG issues someone mentioned earlier.

yes l agree there,  l dident think the steering was going to work well with 2 wheels on each side, looks like normal buggy type steering is heading my way

l havent seen a drain port on the motors but will look again,  the idea of using little rams for the steering instead of linkages sounds good, l will have a hunt on ebay and see whats about,  1" dia  piston 5" stroke sound a good starting point ?

Andy