Large Scale Bobcat PF

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Hi again technic fans,

While browsing BS, I saw a really nice Bobcat and decided to build one. It has been a untapped pet project for a while, and there, a really good inspiration. Can't remember the original builders name (have'nt noted it down) but the powertrain and bucket tilting are his ideas. Starting from there, I've built up the rest, and the final result:

BrickShelf gallery when moderated.

Summary:

2 XL for driving (skid steer)

1 M for raising boom

1 M for tilting bucket

2 PF-Lights

1 Rechargeable BB

The powertrain is not very well designed; there's a lot of gear slippage and zero-radius turning is hell on the gears. There's a lot of bending of the axles that holds the tires, reinforcement of the axle holders should be addressed. When used with a regular BB the weight is to much on the back axles and is really unbalanced.

All in all, it was a quick build, with room for a lot of improvement, and I'm thinking of building it in SR3D to show the mechanisms involved and MAYBE, put out the revised model for instructions. What do you think?

[Alasdair Ryan]

it looks good perhaps you might want to twick the gearing if you say there is gears slipping before you make instrutions,if you do that is

[GuiliuG]

Nice model ! A video would be greatly appreciated to show how it works. I think your model inspiration is from pipasseyoyo :

His gallery

Bobcats are amazing vehicules but really complicated to build. I tried two times to build one and never expected a good result. Maybe should i retry to build one because i have now more experience and parts.

Edited April 18, 2011 by GuiliuG

[grohl]

Nice one. Would love to see the video too.

[Traktor]

It looks really good, but the bending on the axel is a bit concerning. How much can it lift, caus from own experiences I know that liner actors placed like that really strugle to lift almost any amount of weight? I tried to put a xl motor in my 8265 front loader for the raising mechanism and almost destroid the gearing. Not something I recomend to try...

Edited April 18, 2011 by Traktor

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  On 4/18/2011 at 6:09 PM, grohl said:

Nice one. Would love to see the video too.

Here's the video; bear with me it's the first time ever that I make/upload a video.

Lifting 2-M motors seems to be the limit for this boom geometry. I've tried with a BB with batteries, didn't even move a bit.

[GuiliuG]

All the motors are struggling =/

[Alasdair Ryan]

em well e ah o motors ah o em

you need to try changeing some of thoese gears before you break one/or more

have you tryed changeing the 14 tooth gear to a 12 tooth? this might help the drive

what about useing a worm gear for lifting and lowering of the boom, hope this might help

Edited April 19, 2011 by Alasdair Ryan

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  On 4/19/2011 at 7:12 PM, Alasdair Ryan said:

em well e ah o motors ah o em

you need to try changeing some of thoese gears before you break one/or more

have you tryed changeing the 14 tooth gear to a 12 tooth? this might help the drive

what about useing a worm gear for lifting and lowering of the boom, hope this might help

This is just the first "trial" of the design. Obviously the original design for the powertrain from Pipasseyoyo is flawed. I'm thinking of doing some kind of worm drive. The geometry for the boom is correct, but grossly underpowered (got lots of room to change gear ratios). Some aesthetic will be changed. I think I have enough pieces to build a second one in parallel; we'll see over the week-end.

On the other hand, the bucket tilting mechanism is "perfect", the speed is correct with a gear ratio of 72:1. Maybe I'll change the 8t gear for a 16t on worm gear... that'll be fun to develop.

BTW, thanks for all the comments, it's really appreciated.