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Posted (edited)

Finally a competition has drawn me out of a lull. Haven't really had time to build much the last couple of years, and lately I have laced the motivation to build anything at all. Then comes TC22 and I'm bubbling over with ideas. The first thing I thought of reading the rules was a skid steer loader. I'm going for a fully RC loader using BuWizz and 4-5 small PF motors. I'll also try to include an adder/subtractor to make it easier to steer.

This is what I'm gunning for:

C832319.png

cat-skid-steer-esm.jpg

I'm going to use the 42122 as a parts source for tires and a few other parts I lack. If I can solve the drivetrain issue... If not it will be a tracked loader.

42122.jpg?fit=bounds&format=jpg&quality=

 

For now, this is what I have. I'm trying to keep within 17 studs with, and will compensate the other axis to keep within the allowed 10 000 cubic studs.

skid_loader_adder_subtractor_base.png

I will update with more build pics as soon as possible. Haven't had time to do physical testing yet...

EDIT - A few updates after starting physical build:

It seems the completed size will be real close to the max 10000 cubic studs. Right now my goal is to keep within 28x17x21 = 9996 cubic studs. It's very hard making it less wide with these tires, and I will be needing the length to make sure the full bucket is within the box, so all I have left to play with is height. I could swap for some slimmer tires, but I feel these fit the model very well. But if I have to there are some alternatives. 

I decided to use an exoframe rather than an internal frame, and this allowed to make the adder/subtractor much more compact, and allowed me to switch to the one stud longer large motors. The plan is to use a chain to connect the front and rear wheels as this gives way less backlash.

Now all I have to do is finding a way to implement the other two motors...

Test build/prototype:

DSC-1766.png

DSC-1767.png

First edition base after physical testing:adder_subtractor_base_exoframe_edition_1

adder_subtractor_base_exoframe_edition_2

 

_ED_

Edited by Nazgarot

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If You have two motors, why just don't use one for each side? Then You can remove those differentials, and have more space for other things. I think, it would be OK to use also these tires

250x250p.jpg?1642519085.7222009

Then it would be narrower, and You would have more space in other directions. Maybe they would look somehow small for this scale?

10 hours ago, Nazgarot said:

Test build/prototype:

I don't see some 2 pictures after that line.

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Posted (edited)
6 hours ago, Jurss said:

If You have two motors, why just don't use one for each side? Then You can remove those differentials, and have more space for other things. I think, it would be OK to use also these tires

Then it would be narrower, and You would have more space in other directions. Maybe they would look somehow small for this scale?

As you say, those would be to small for the scale I'm going for.

As for only using two motors, a part of the challenge I set for myself was including a adder/subtractor. Fitting only one motor for each side would allow for a much smaller scale, and would make it way easier... It being hard is a part of the reason I do this :pir-sweet:

6 hours ago, Jurss said:

I don't see some 2 pictures after that line.

I'll try uploading through a different service. Give me a heads up if it still doesn't work.

Edited by Nazgarot

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I think you need all wheels to be driven as otherwise the non-driven wheels will add resistance against steering.

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2 hours ago, SaperPL said:

I think you need all wheels to be driven as otherwise the non-driven wheels will add resistance against steering.

The plan is to drive the rear wheel through chain drive from the front wheels. This gives a lot less backlash then using gears, but I have to test it to see if the chain can handle the stress. If not I might have to convert it to tracks...

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Posted (edited)

Some updates. I've decided to go with a Cat 216b as a base for the model. This involves using large LAs and making it quite a large model. I have to do a resize to 18x27x20 studs from the 17x28x21 I was planning for. 

skid-steer-loaders-226b-series-3-caterpi

Some progress - finally happy with the base of the vehicle, and pleased with how I managed to compress and cover up the adder/subtractor drivetrain.

DSC-1772.jpg

DSC-1773.jpg

I've started work on the rear of the model and concepted a solution for placement of the last two motors. The last is giving me some challenges, but that is why we do this, isn't it?

EDIT:

Another small update:

I needed to move power from a motor to a function (LA) to the opposite direction, 3 studs up and 3 studs to the side, and am quite pleased with what I came up with. As it might be of interest to others I will post it here. It uses one somewhat exotic part that I happen to have a lot of for some reason, and solves my problem for placing the motors within a very tight space.

LA-drivetrain.png

This solution holds the motor as well as the whole drivetrain in place, and only requires 4x3x3 studs. It also prevent gear skipping by holding the lliftarm in place with a 1x1 modified round plate. It makes for a super compact placement of the motors that will allow me to keep a somewhat realistic look within the limited dimensions.

Now all I have to do is coming up with an equally compact solution for the other side... Then I'll have solved most of the mechanical issues, and only aesthetics are left.

By the way, there is also the issue of placing the PF-power switch that I use to reverse one of the drive motors, and did not originally plan for... It's almost the size of a motor!

 

_ED_

Edited by Nazgarot

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Posted (edited)

Another update. Now the base is almost done, and I have managed to find place for a total of 5 motors (2 Large ones for drive, 3 small for steering/lift/bucket), a complete adder/subtractor, the BuWizz, a PF switch, and still have kept everything low enough to have room for a full cabin. If I could find a way to control a sixth motor I could even include a opening bucket like some of these have.

DSC-1790.jpg

DSC-1792.jpg

DSC-1789.jpg

As you can see of the last picture the trackwidth gets quite wide with these tires. I'm at 18 studs now, and could reduce it to 17 using a trick by putting the inner side of the tire inside of the rim. But I don't know if this is legal according to the competition rules... I could also use other tires for 16 studs, and will probably include pics of the finished model with several different setups, but I feel these fit the model very well.

I've also made a custom openable bucket that could be controlled if I find a way to control a sixth motor (5th function), but I lack parts to realize it at the moment, so I have to tear something apart before I can build it. Pics upcoming.

Now all I have to do is finish the boom, the connection for the bucket, and the superstructure as well as the cabin. 

I do have one problem though... It is so rear heavy that it wants to tilt backwards. It was meant as a feature, but not to this degree... Any suggestions to fix it are welcome. 

_ED_

Edited by Nazgarot

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37 minutes ago, Nazgarot said:

I do have one problem though... It is so rear heavy that it wants to tilt backwards.

Even after you add:

37 minutes ago, Nazgarot said:

the boom, the connection for the bucket, and the superstructure as well as the cabin.

It is still rear heavy? Make bigger bucket! :wink:

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It tips back as is, and I still have to add the seat, the control systems, the gear train for the bucket function, and the mounts for the boom. The weight of this will be far more than the boom and bucket, so it will be VERY back heavy, That in combination with 2x L motor for drive equals instant wheelies... :pir-oh: Cool, but not exactly what I was looking for. Might be able to weight down the boom a bit, but I'm open for other suggestions... 

_ED_

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Wheelbase is really short on your model.

Real ones have shorter and littlebit longer wheelbases, depending on model. f.i. bobcat s530 has pretty long wheelbase for these type of machines.

but, maybe with everything else added, it won't be so bad.

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12 hours ago, Jurss said:

Wheelbase is really short on your model.

Real ones have shorter and littlebit longer wheelbases, depending on model. f.i. bobcat s530 has pretty long wheelbase for these type of machines.

but, maybe with everything else added, it won't be so bad.

I know. It was meant as a feauture, as I'm basing the build on the Cat 226b

caterpillar-216b-3,2e51607c-3.jpg

As you can see it has a short wheelbase with a large overhang, and I thought this would make it possible to do some wheelies if you really jam the throttle. It also has a very low ground clearance in the back, making it ideal for a model with the drive motors very low. As is it is way to rear heavy. But going with a custom bucket should help some as it will be quite heavy compared to a standard single piece bucket. I'm even thinking of including opening the bucket as a manual function.

 

 

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Posted (edited)

A little more progress... 

DSC-1794.jpg

The Rear part will be covered by a black plate, and the lower yellow liftarms will be swapped for black ones for a complete black rear end.

DSC-1795.jpg

 

I'm within planned dimensions, but it's gonna be tight. At the moment I've set the limit at 18 wide, 27 long with bucket and 20 high = 9720 cubic studs. If I can make it a little narrower I'll go for 17x28x21 = 9996 cubic studs.

DSC-1796.jpg

 

Unfortunately I won't have much time to build the next couple of weeks, so I just hope I can finish it enough to see If I need to order any parts before times up. Hopefully I can get the bucket ready for testing tomorrow. The body is currently 20,5 studs, so in the last 6,5 or 7,5 studs I have to make the bucket fit. It will be a tight fit...

_ED_

 

 

Edited by Nazgarot

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I know this might be cheating. But we use skid steers with fork attachments a lot. 

You could do a forklift attachment with fold up forks to get inside the box limits.

Don't get me wrong a bucket would be the icing on the cake. 

Regard matt

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6 hours ago, Nazgarot said:

t will be a tight fit...

When the tilt down of the bucket is accurate, you can make it fit while the bucket is half elevated ;-)

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10 hours ago, Jundis said:

When the tilt down of the bucket is accurate, you can make it fit while the bucket is half elevated ;-)

Have been thinking of it, but I feel that is cheating as well.. 

@Jim How do you rule? Is a tilted bucket ok?

_ED_

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25 minutes ago, Nazgarot said:

Have been thinking of it, but I feel that is cheating as well.. 

That isn't considered cheating. You need to fit the model without taking things off. But you can position the boom/bucket etc any way you want.

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2 hours ago, Jim said:

That isn't considered cheating. You need to fit the model without taking things off. But you can position the boom/bucket etc any way you want.

:thumbup: That solves all problems regarding size! :pir-grin:

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Haven't had time for any more physical building, but here are the bucket variants I'm considdering. Non of them are "perfect" copies of the real bucket, but both have a "hidden function" of being able to open. The overall shape is close to the real buckets, but I'm still undecided on which is best. Any inputs? I would also like suggestions for improvements if you have any...

Bucket-variants.png

 

_ED_

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