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pic: Bit Buckets 2015 Offseason Drivetrain
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Re: pic: Bit Buckets 2015 Offseason Drivetrain
Looks great! 47lbs is a very good weight with electronics on there. Electronics all seemt of it well, but you have some wasted space underneath that top plate.
I noticed that your hex axles have a deep groove cut right before the end. This will weaken the axle by a lot. Why is it there? Pulleys also seema bit large... the belts won't intersect with anything, right? EDIT: Out of curiosity, how does this go together? Do you make puzzle-piece edges and glue them? How do you get machine screws into joints? |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
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Re: pic: Bit Buckets 2015 Offseason Drivetrain
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The pulleys are 42t, the same size as on the AM14U. We checked that the belts clear the belly pan. Ryan Dognaux's explanation of the axles in the post below yours is accurate. It's all put together with mortise and tenon joints and captive nuts, as described in this (excellent) Instructables page. More renders, as promised: The drive pod, showing most of the powertrain, as well as some example T-nut joints: ![]() The gearbox, which needs a little more work on mounting holes, as well as an encoder mount (Anyone have ideas on how to attach an encoder? Could it be attached directly to a CIM shaft? The gearbox's output shaft remains in the drive module when the gearbox is removed, so the encoder can't be mounted on that.): ![]() |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
This might help with the encoder issue.http://www.chiefdelphi.com/forums/sh...hreadid=131034
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Re: pic: Bit Buckets 2015 Offseason Drivetrain
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![]() Since we don't have much experience milling complex parts, I'd like to 3D print the encoder mount. I think it would be structurally sound; others have printed much more complex motor mounts. |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
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Re: pic: Bit Buckets 2015 Offseason Drivetrain
![]() We cut about half of a drivetrain today as a prototype. It generally goes together well for a first prototype, though we found some bugs we want to fix before building a full chassis (including a misalignment in the laser cutter that led to beveled edges). |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
It looks like it is going good. I am interested in seeing how this turns out because we have gained access to a similar machine. It is a 4'X8' Shopbot. And being able to confidently believe a drive train out of wood will hold up would be really nice to know.
I do have a few questions Where did you get the wood/what product is it? Do you plan to use this for FRC next year? How do you plan to test it? How will you know it won't break? |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
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We do want to use this as our competition bot design (more or less), if it works. We plan on building a few iterations now to get the hang of it. We want to make a practice robot that we can bang up to get endurance information. |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
Since we cut the prototype last week, I've been hard at work improving the design. We'll be fabricating this iteration tomorrow.
![]() Full size here! Some information and a partial change log: -Weighs 36.7 lbs with everything shown except bumpers and battery -Contains 34 plywood parts, which weigh a total of 15.9 lbs -Gearbox removable from top or bottom with 4 bolts. Drive pod removable from side with 5 bolts -Improved gearbox with stronger design, easier mounting, more choice in ratios and a slightly increased top speed of ~12fps adjusted -Modified encoder mount for 3D printing -Revised powertrain to use wheels and pulleys from AM14U so we don't have to order more parts -Designed sturdy and easy to change bumpers -Reinforced battery mount -Added removable center belly pan section that allows access to the middle box -Revised joint layout for improved strength and easier design changes -Added lightening holes in larger wood parts We plan on sharing photos and the latest version of the CAD files tomorrow afternoon and our engineering journal at the completion of the project. Any questions or ideas? |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
Can you swtich to COTS shifting gearboxes? A good portion of the advantage of a six cim drive is lost when using single speed, because going at any speed where the acceleration difference (between 4 and six cims) is not negligible is just asking for breaker blows.
On another note, that's a really good weight and design. The way you are fitting wodden plates together is very novel. How do you make the correct tolerances on everything? |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
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Tolerances are largely determined by trial and error. Since laser-cut wood is so fast and cheap to make, we can make multiple iterations of a part in a day. We're cutting the slots and tabs to nominal dimensions; the laser kerf makes them a tight, but still easy-to-assemble fit. For bearing hole sizes, we're cutting a test part today with holes of slightly different sizes to see which works the best. |
Re: pic: Bit Buckets 2015 Offseason Drivetrain
What is the cutting area of the laser cutter?
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