12-03-2016 00:23

pilleya

Re: pic: Triwheels

Looks like an innovative solution to getting over the obstacles

You might want to be careful about your choice of axle material, 1/2 inch Churro shaft really isn't known for being a good material for live axles, it is very useful for spacers and stand-offs, but not for things which take a lot of load.

This thread has a little bit more information
http://www.chiefdelphi.com/forums/sh...xle+materi al

If you have can afford the time and have the weight, it would recommend the switch to 7075 1/2 Hex shaft(Available from WCP/VEXPRO/Andymark) before your North Bay Regional

12-03-2016 00:40

frcguy

Re: pic: Triwheels

Cool idea. I concur about the churro probably not being the best axle material however. We have seen that you can tweak a churro just using holding together a chassis, and I would assume there would be a similar load on your axles. Also I second this hex shaft from VexPro. We used some of it this year and it's held up real well.

12-03-2016 03:16

Foster

Re: pic: Triwheels

What does the gearing on the other side look like?

12-03-2016 03:57

yomega55

Re: pic: Triwheels

I third the vexpro hex shafts

12-03-2016 04:13

pilleya

Re: pic: Triwheels

Yes,
Any Aluminium or Steel( or even Ti) 1/2 hex shaft( no center hole) would reduce the risk of failure. 7075 shaft is ideal and is substantially stronger than 6061. Both VexPro and Andymark sell 7075 grade hex shaft and the Vexpro is "Anodised for superior performance" and it looks nicer.

12-03-2016 06:43

C.Lesco

Re: pic: Triwheels

Sorry if i knew how to upload a picture directly to the chat i would, i can send you a picture lster today since im taking off to watcha regional but short story.

Altogether 7 gears per wheel, i forget the exact ratio but its 2:1ish. All gears from vex, center gear drives 3 small idler gears which inturn drive 3 large gears. Quick fun fact, there are no bearings on the 0.5 inch hex idlers and they just free rotate around a bolt

12-03-2016 06:45

C.Lesco

Re: pic: Triwheels

And i will look into buying a half inch hex for the axles, thanks for the input guys!

12-03-2016 06:49

pilleya

Re: pic: Triwheels

Why go for idler gears, surely it would be simpler to just have 1 large gear turning 3 large gears attached to the wheels and do the 2:1 reduction else where, such as with the belts/ chain driving the modules or in the gearbox ( custom 3rd stage to get adequate reduction etc)

Also were the plates made by hand?, looks like some pretty precise metal work

What you ended up with looks very nice, what made you change your plan about making custom gears rather than purchasing COTs ones, you seemed set on making them earlier in the season.

12-03-2016 19:42

Cothron Theiss

Re: pic: Triwheels

I'm not on the OP's team so I don't know, but I assume it is because if the driving gear was large enough to contact the three driven gears, they wouldn't get the 2:1 reduction they need. The driving gear has to be small enough for the desired reduction.

12-03-2016 20:09

pilleya

Re: pic: Triwheels

http://www.chiefdelphi.com/forums/sh...d.php?t=142662

The OP was originally planning on custom machining the gears for this, they may have been planning to make large ones( almost wheel diameter) to get the required reduction with 4 gears, but they didn't end up doing this. Probably a good choice to, machining gears is hard work and very time consuming.

14-03-2016 03:13

Mike Marandola

Re: pic: Triwheels

How are they on stairs?

14-03-2016 03:29

pilleya

Re: pic: Triwheels

With 6 wheeled trolleys, it is usually the pulling motion that allows the trolley to climb stairs, the person pulling it up the stairs is standing at around 45 degrees upwards of the trolley, so there pulling is what is actually causing the tri-wheels to jump up each step, if you tried pushing it up it wouldn’t do much. The key I see to the tri-wheel style obstacle crossing mechanism is that the distance from bottom of the wheel to the tri-wheel pivot, must be greater than the maximum height of the obstacles is has the cross(sort of obvious). Last year we asked to borrow a trolley from our school’s maintenance department/people and they gave us a 6-wheel trolley where each wheel was a very rugged 125mm Omni-wheel.

16-03-2016 01:26

C.Lesco

Re: pic: Triwheels

The assembly would flip in the wrong direction if it didnt have idlers. I personally plasmacut the plates mtself with team members helping to file so thanks and im suprised you remember that custom gear thing. We took the advise given to look elsewhere and we were ashamed to find vex selling the gears we needed off the shelf. So lesson learned lol

17-03-2016 09:22

pryland

Re: pic: Triwheels

We started on this path, but 3 weeks into build we discovered the colson's would just sit and burn rubber. Not rotation around the center unless we wrapped the colson's in sticky tape. Decided to pursue plan "B".https://drive.google.com/file/d/0B4h...ew?usp=sharing

17-03-2016 09:46

daliberator

Re: pic: Triwheels

Are those 3D printed sprockets? That's a cool way to prototype.

17-03-2016 09:51

Cothron Theiss

Re: pic: Triwheels

Getting files for Vex gears and sprockets is a great idea. You can change the tooth count in about a minute in the file, and then print them off in a short amount of time.

17-03-2016 10:34

pryland

Re: pic: Triwheels

Prototype? Nope. Production!