Jump to content
MadInventor

Grapple Skidder scratch build

Recommended Posts

Hi all,

I've started another project, despite being only half way through the half track (no pun intended). This is the start of what will hopefully end up being a grapple skidder. (A forestry machine with an articulated chassis). I put in this forum as it covers 'heavy plant'

I started off with a REVO diff I had left over from an aborted tractor build, and added some short custom outdrives I made in steel for each side.

img33435_17032013211416_1.jpg

I then made four axles (8mm steel) with 16mm drive cups on the ends, loctited on.

img33435_17032013211416_2.jpg

After that, four adapters were machined to attach square steel box section to the sides of the diff.

img33435_17032013211416_3.jpg

img33435_17032013211416_4.jpg

img33435_17032013211416_5.jpg

These slip over the bearing holders on the diff housing and are held in place by the 4 bolts that hold the diff together.

Then 4 bearing holders were made to press into the other end of the box section:

img33435_17032013211416_6.jpg

Pressed into box section:

img33435_13092013190448_1.jpg

Axles part way through completion:

img33435_13092013190448_2.jpg

Wheel hubs fit Jugg2 wheels and are secured to the axles with grub screws. The wheels are held on by bolts rather than nuts:

img33435_13092013190448_3.jpg

img33435_13092013190448_4.jpg

Wheel bolts are unobtrusive:

img33435_13092013190448_5.jpg

Completed axles:
img33435_13092013190448_6.jpg

Although the axles don't look very strong where they attach to the diff, the rear axle is directly attached to the chassis with no suspension, so the chassis will provide good support and rigidity, and it will be necessary to add a frame to the front axle to attach the suspension pivot, so that will give the front axle the rigidity it requires. I think the 1.5mm thick steel box section and heavy duty 8mm drive shaft will guarantee me no broken axles. My future ideas for this at the moment are to power it with an RS850 motor and an 11.1 LiPo, suitably geared down to provide lots of pulling power, and a motor and screwjack to operate the steering for the articulated chassis.

  • Like 1

Share this post


Link to post
Share on other sites

Martin do you have a press at work with a gauge ? Try to compress that 1.5 mm box section . Its strength will surprise you . Being box section its also very rigid under torsion . But you know all this already lol

Share this post


Link to post
Share on other sites

Your machining skills are out of this world!

Looks to be another MadInventor creation!
Will be watching to see what happens with this...

Cheers,

Skottoman

Share this post


Link to post
Share on other sites

Managed to get a bit more done in the last few days.

This is the bracket for the front suspension pin, it's aluminium with a steel pin insert, held in with Loctite 638:

img33435_17092013204212_1.jpg

img33435_17092013204212_2.jpg

This is the bracket bolted to the front axle. It also will help to keep the axle straight and take the strain of the connections from the steel tubes to the diff housing.

img33435_17092013204212_3.jpg

These are 2 of the front chassis bulkheads. The chassis plates will bolt to the sides of the black plastic blocks, and then the front axle will pivot on the pin in the front suspension bracket, and on the diff housing where the central output shaft bearings are held. I've aimed in the design of the chassis to replicate the +-15 degree pivot on the front axle of the full size machine.

img33435_17092013204212_4.jpg

The bulkheads are very basic at the moment, they will be machined out for lightness once I get further into the build. the last thing I want to do is lighten them now, and then discover I need to bolt something to where I'd machined a hole early in the build. (Got caught out doing that once before)

The next step will be to either cut out the front chassis plates, or construct the central hinge for the chassis.

I'll be trying to motor on with this now before it gets too cold and damp in the workshop....

Update 25-09-2013

I've nearly got the chassis hinges done. They each have a 1260 ballrace in the centre of them. Just got to drill and tap the forward part of the hinge, but will leave that until I've created the forward bulkhead. I've also done the front bulkhead for the rear part of the chassis. The hole in the centre of it is for the rear drive shaft to pass through. This needs drilling and tapping for the chassis plates to attach to , but I will do this once I've cut the chassis plates for the back end. The rear bulkhead is a 10mm thick block of aluminium. Should be fairly sturdy :)

img33435_25092013195633_1.jpg

img33435_25092013195633_2.jpg

img33435_25092013195633_3.jpg

img33435_25092013195633_4.jpg

Share this post


Link to post
Share on other sites

Quick update, got a little bit of the rear chassis done today, can start to see what it's going to look like now:

img33435_01102013212043_1.jpg

img33435_01102013212043_2.jpg

Share this post


Link to post
Share on other sites

nice work Martin - essentially a Volvo type coupling / power line ?

Share this post


Link to post
Share on other sites

nice work Martin - essentially a Volvo type coupling / power line ?

I'm guessing so, I've based the design on a John Deere grapple skidder, but essentialy the propshaft wil be secured on the front chassis bulkhead, then pivot in the centre close to the hinge pins centre point.

I got the gears for the transmission through HPC today, I think I've overdone it on the heavy duty, the last 2 gears in the transmission are steel 1 module gears with 15mm wide teeth, and the spur gear is also steel with 8mm wide teeth :). The last transmission gear weighs 300g on it's own, so I need to drill some holes in it to lighten it before I can fit it. Suprisingly, this build is going fairly smoothly so far without too many mistakes or design errors, I'm hoping to have a rolling chassis done by xmas.

This is the general idea.

http://www.youtube.com/watch?v=H8dt4pXSMOE

Share this post


Link to post
Share on other sites

Loving your work as always Martin, watching with interest (again) :lol:

  • Like 1

Share this post


Link to post
Share on other sites

Loving your work as always Martin, watching with interest (again) :lol:

I know, I stopped the half track part way through, I'm thinking I'll get the rolling chassis on the skidder done, then maybe spend a little more time on the half track to get it running at least.

Share this post


Link to post
Share on other sites

Got the rear lower chassis plate made today. It's 1.5mm thick steel plate.

img33435_01102013212043_3.jpg

img33435_01102013212043_4.jpg

Also drilled out the gears for the transfer case to lighten them up a bit

img33435_04102013214218_1.jpg

These are steel, module 1.0 (A bit beefier teeth than old school motor pinions), the wider ones have 15mm wide teeth, the narrower ones 8mm. the motor will drive the smallest gear directly.

I thought it would be a problem drilling the holes in the largest gear as I had to drill through 15mm of steel, but the machine coped well with it. I wouldn't have wanted to try it with a hand held drill though, as the holes are 8mm diameter. The largest gear weighed 200g before I put the holes in it, not sure what it is now.

Update 07/10/13

Sorted out the chassis plates so that they fit well now, and also made an underguard for the rear diff from a 12mm thick aluminium plate. It helps to stiffen and strengthen the rear axle, and to attach it securely to the chassis. The axle will also be attached to the top chassis frames, which will extend over the top of the axle right to the rear of the chassis.

img33435_07102013222831_1.jpg

img33435_07102013222831_2.jpg

img33435_07102013222831_3.jpg

img33435_07102013222831_4.jpg

Update 12/10/13

Fitted the last of the upper rear hull plates, and nearly got the rear bulkhead for the front chassis finished, just a few holes to drill and tap, but it fits ok to the centre hinge:

img33435_12102013112008_1.jpg

It also doubles up as one half of the gearbox:

img33435_12102013112008_2.jpg

img33435_12102013112008_3.jpg

Very pleased that the hinge is nice and smooth

img33435_12102013112008_4.jpg

I'm going to make the bottom chassis plate next, so that I can attach the front axle and see what the wheelbase is going to look like.

img33435_12102013112008_4.jpg

Share this post


Link to post
Share on other sites

I am always blown away by the amount of work and engineering you put in to you builds.

I take my hat of to you. My metal skills are no where near your level.

Will watch this build :)

Share this post


Link to post
Share on other sites

Only 1 more part made since the last post, but I've now got it up on 4 wheels, woohoo. :) It's always nice when building something to actually get all the wheels on, as it gives an (very rough) idea of what the finished model is going to look like. Here's a couple of shots of it against the 6x6 to give an idea of size, and how the hinged chassis is going to work.

img33435_13102013132024_2.jpg

img33435_13102013132024_1.jpg

Share this post


Link to post
Share on other sites

Martin this is a little off the wall in terms of where you are already but did you consider having the hinged section being able to also pivot in the X axis ? Volvo do that by having what is effectively a bearing mounted to each chassis section . The steering hinge fixes to the outer bearing race and the drive shaft passes through the centre of the bearing . You end up with a very tight turning circle and over 160 % articulation on either end .

Just a thought for another build maybe ?

Share this post


Link to post
Share on other sites

Martin this is a little off the wall in terms of where you are already but did you consider having the hinged section being able to also pivot in the X axis ? Volvo do that by having what is effectively a bearing mounted to each chassis section . The steering hinge fixes to the outer bearing race and the drive shaft passes through the centre of the bearing . You end up with a very tight turning circle and over 160 % articulation on either end .

Just a thought for another build maybe ?

I found with the 6x6 that having massive articulation on a free floating suspension is not necessarily great for off roading. When driving sideways across a slope, the torque on the front propshaft has a tendency to turn the chassis round the front axle and tip the vehicle over, as there are no springs to restrict the movement. If I ever get round to making an 8x8 forwarder with a chassis pivot I would go for this method though, with the trailer able to articulate separately from the body. I still have in my work in progress bin this grapple skidder, the half track, and I STILL haven't finished the gearboxes for the steel king tiger, and I started the king tiger thread nearly 3 years ago, so the 8x8 will have to wait for a while :)

Share this post


Link to post
Share on other sites

I found with the 6x6 that having massive articulation on a free floating suspension is not necessarily great for off roading. When driving sideways across a slope, the torque on the front propshaft has a tendency to turn the chassis round the front axle and tip the vehicle over, as there are no springs to restrict the movement. If I ever get round to making an 8x8 forwarder with a chassis pivot I would go for this method though, with the trailer able to articulate separately from the body. I still have in my work in progress bin this grapple skidder, the half track, and I STILL haven't finished the gearboxes for the steel king tiger, and I started the king tiger thread nearly 3 years ago, so the 8x8 will have to wait for a while :)

Last update for today, managed to find an hour to make the lower plates for the front chassis, got some strength in it now.

img33435_13102013132024_3.jpg

img33435_13102013132024_4.jpg

img33435_13102013132024_5.jpg

Edit 15/10/2013:

Roughed out the top panels for the front of the chassis. This shows what the length of the front of the chassis will be, I've still got to trim the top of the panels down a bit at the front, but that's most of the chassis plates done now.

img33435_13102013132024_6.jpg

Update 17/10/2013:

Nearly finished the 2nd gearbox bulkhead, got it shaped and the bearings fitted, just got to go round the outside of it now and drill and tap all the holes (10) to attach it to the chassis plates. Then I can work on the spacers for the inside of the gearbox, and also attaching the shafts to the first and last gears in the gearbox. The top shaft is the one the motor will drive directly, and the bottom output shaft will drive the front and rear axles. The little slits visible in the top view are for a plate to slot in to seal off the gearbox from the right hand side of the chassis, as the screwjack that it is going to operate the steering has to fit down there. The gears all run lovely and smoothly as well, which i'm really pleased about, as even a minute error would have caused them to bind. :)

img33435_17102013213718_1.jpg

img33435_17102013213718_2.jpg

Share this post


Link to post
Share on other sites

Done a little bit more today, Machined the flat and drilled a hole in the 1st shaft of the gearbox to accept a traxxas revo drive shaft, and loctited the gear in position. Also made the spacing shims I needed for the gearbox to ensure the gears don't rub each other or the sides of the gearbox. 1 more drive shaft end to do and Loctite on the final drive gear, and that's the gearbox moving parts completed. Just got to mod a couple of drive shafts then and that's the transmission finished.

Share this post


Link to post
Share on other sites

I reckon in a post apocalyptic world where everything is barren some alien species is going to fly down and find your custom toys just sitting there unscathed! That things a beast! :)

  • Like 1

Share this post


Link to post
Share on other sites

I reckon in a post apocalyptic world where everything is barren some alien species is going to fly down and find your custom toys just sitting there unscathed! That things a beast! :)

:) Wait 'till you see the motor I've got coming for it .....

Hit a major milestone in this build today:

img33435_25102013211240_1.jpg

img33435_25102013211240_2.jpg

img33435_25102013211240_3.jpg

Got all the driveshafts going into or out of the transmission finished, loctited all the gears where necessary that were not already done, and made a propshaft to go to the rear axle. When the rear wheels are turned now, the input shaft to the transmission that the motor will be connected to also turns. :)

In other good news, the UJ in the centre of the chassis pivot still turns freely at the extremes of the chassis articulation left and right.

Just waiting on some more drive shafts now to make up the drive shaft to go the front axle.

Share this post


Link to post
Share on other sites

I'm so looking forward to seeing this in action!

Me too ! I made the bulkhead that fits right at the front of the chassis today and drilled holes to fit it, and also cut a bit more off the front of the chassis to steepen the angle of the lower part of the front chassis. Also cut out the steel plate to cover the bottom of the far front of the chassis. I also drilled some holes in the plastic plate that the front axle pivots on in the wrong place, so have got to fill them in and put some more in the right place :(. 1 step forward and one back .....

On a slightly different track I've also figured out how I'm going to fit the front shocks on the half track I was building, I'm going to use a couple of TXT cantilevers and a couple of old yellow CVA short shocks mounted horizontally down the chassis rails. I might have to get this done once I've got the front chassis finished if the motor hasn't turned up by the time the bottom plate has gone in. It's either that or on with the logging blade to fit on the front. (This will be a bit of a monster as the blade is supposed to be 295mm wide) :)

I've looked at the space I've got to fit the steering actuator and that is going to be 'interesting'. I'll get the blade and the main motor fitted first before I attempt that I think :)

edit 27/10/2013:

Just adding some pics of the front underguard (1.5mm steel plate), and the very front bulkhead (Delrin):

img33435_27102013190207_1.jpg

img33435_27102013190207_2.jpg

I managed to put a bend in it ok at the right place, so now just have to 'adjust' the front axle mounting bulkhead slightly to slot into it, and that should be the front end quite solid.

Share this post


Link to post
Share on other sites

Did you get your motor yet? Curious to see how big it is compared to the rest of the chassis... :)

I'm still hovering over the letterbox like an expectant Dad ;)

Delivery is supposed to be 12 days, which will be up on Friday......

The motor should sit nicely over the front bulkheads holding the front axle, I plan to recess them to lower the motor, but they are 70mm apart from outer edge to outer edge, which is slightly shorter than the length of the motor.

My drive shafts I ordered turned up yesterday, so it now has the front drive shaft fitted and 4wd :)

On the down side I drilled holes in the wrong place on the forward front axle bulkhead, and then machined too much plastic off the bottom, so now have to make another one :(

I've gone back to fitting the front shocks on the half track for the time being now, until the boat motor turns up.

Will hopefully be able to post some progress on that thread in the next couple of days..

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...