New Projects looking for a Picaxe

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tarzan

Senior Member
Twin Tracked Vehicle

Looking for some bevel gears to complete drive mechanism must fit 6mm shaft 1:1 up to 1:4 ratio.
 

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tarzan

Senior Member
Hi Joe,

I want to mount both motors facing the same direction; this means those bevel gears at 31mm diameter will be too wide sitting side by side to fit in the space available. If I mount head to toe motor arrangement they would fit but that would be bad for drive characteristics, one side pulling the other side pushing. Need smaller drive gear but final output gear can be up to 31mm diameter. To reduce loading it maybe best to have 3:1 reduction. My motors are Maxon DC with encoders and 90:1 planetary gearboxes.
 
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JoeFromOzarks

Senior Member
The JR Vibe 90 helicopter has a fairly small gear assembly driving the tail rotor off the main engine.

I'm guessing your tracks will demand a fair amount of torque, the picture on the left might be a better option. I believe the belt itself is only 1/8" wide!

:) joe
 

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tarzan

Senior Member
Twin Cab Tracked Vehicle

Twin Cab Tracked Vehicle

At this stage in the development one half of the chassis is under construction, now working on completing the drive mechanism. Bevel gears are what I would like to use; both pinion gear and final output gear will mount on 6mm shafts at 90 degrees. Two sets are required for each chassis eight bevel gears in total. The Maxon DC motors I’m using have encoders attached at the rear and 90:1 reduction planetary gearboxes with 4mm output shaft. There will be an attached 6mm shaft running in two bearings carrying the pinion gear. Using the attached shaft, allows for consistency in sizing of gear carrying shafts and a more robust setup with some adjustment for gear alignment.

http://picaxe.multiply.com/photos/album/16#
 

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JoeFromOzarks

Senior Member
These folks have quite a selection:

http://www.hpcgears.com/

I've never bought from them, but the pictures are fun to look at!

Won't putting the motors at the same end of the vehicle mess with the balance, making one end heavier than the other?

Sure wish I knew more about 'em!

:) joe
 
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tarzan

Senior Member
Hi Joe,

Thanks for the link. They have a large selection of gears, but only one that I see that will fit at an affordable price. ZEB1-16 ØB is 5mm I will have to bore them out to 6mm, not something that I really want to do because they may not run true afterwards.

On the matter about balance the two units will be tethered together giving some extra degree of balance and will weigh in at considerably more than present with batteries on board.

I’m already thinking that these motors maybe on the wimpy side but with four driving I may squeak by. The test will come when it has to climb a hill.
 
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JoeFromOzarks

Senior Member
Hi Dan,

I'm getting in over my head - I don't build such things! :)

I don't know how much dirt and other contaminates might get inside, but I think I'd be looking at worm gears between the motors and the differential gear. If it's looking like the inside of the machinery might be exposed to contamination, a sealed 90-degree RC gear box may be the only option.

Another user on this site builds robots for cleaning air ducts, can't think who it is at the moment, he might have some guidance though.

:) joe
 
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tarzan

Senior Member
@BeanieBots

Thanks for the offer. I will stay in the sandbox until I have a completed project or have a Picaxe on board.

@JoeFromOzarks

The gear mounted in the picture is a worm gear 50:1 to low to use and I’ve not been able to find anything locally that is suitable.

There is a gap on the underside along each side beam and base plate on this prototype, which maybe addressed in the next version by using wider aluminium angle stock. It will need trimming along the top to make fit. This has to be done with hand tools, as I do not own a milling machine or lathe to work on. If I do this, the gearbox and motors can be sealed from the elements.
 
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cdngunner

Senior Member
Nice work!

Just remember there are major losses when you use bevel or miter gears.

This is the place I get most of my drive components

https://sdp-si.com

I have no 6mm but I do have some brass .25 id miter gears
 
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tarzan

Senior Member
cdngunner said:
I have no 6mm but I do have some brass .25 id miter gears
Click to expand...
I.D. Quarter inch to large, no point putting a sleeve in. Brass would be nice; though too expensive.

I see two options at SDP/SI:

MATERIAL: Acetal

A 1M 4MYH10 Straight Miter Gear with 6mm bore 1:1 ratio use with attached 6mm shaft mounted with two ball bearings

https://sdp-si.com/ss/PDF/78501140.pdf

A 1M 3MYH0820 Molded Bevel Gear 4mm bore 2:1 ratio connected to motor output shaft
A 1M 3MYH0840 Molded Bevel Gear 5mm bore 2:1 ratio bore out to 6mm to fit final output drive shaft

https://sdp-si.com/ss/PDF/78501144.pdf
 
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cdngunner

Senior Member
Acetal is nice because you dont have to worry about grease or oil.

I'll check to see if I need to order anything. If I do I can add you gears and send them to you, will be a lot cheaper for you.
 
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tarzan

Senior Member
That’s a very kind offer. Don’t know how to get all those loonies to you, may have to send Picaxe product in exchange.
 
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tarzan

Senior Member
The distance between the two bearing hubs on the inside measures 62.5mm.
The bearing inside race sits about 0.5mm below the hub give about 63.5mm in total to mount two sets of gears across the width. Each set has 31.75mm of space across the width available; lengthwise there is plenty of room.

Worm gear orientation may mean vertically mounting drive motors, there should be enough height available to mount horizontally if a small final drive gear is located.
Centre of final drive shaft to ceiling approximately 29mm and 26mm to flange.
 
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JoeFromOzarks

Senior Member
Tarzan, what's happening in the progress department? Is the differential issue sorted? (Is that British for "figured out?")

:) joe
 
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tarzan

Senior Member
Hi Joe,

Not a lot has been sorted since I last posted. I have ordered one Pololu USB Motor Controller with Feedback - Jrk 21v3 to evaluate the PID. I’ll need three more, one for each track.

I got some 50mm x 50mm x 3mm aluminum angle to remake the chassis for the two drive units. My digital caliper display stopped working so I must purchase a new one before I can proceed with making the new chassis.

I have some nRF905-C433 Transceivers that I looking for suitable antennas for. I’ve ordered from Spark Fun U-FL SMD Connectors and four-inch Interface Cables RP-SMA panel mount to U-FL; but no RP-SMA 433MHz Antennas are available from Spark Fun.

I’m going to trial the Compass Module - HMC6352 before I consider buying the much more expensive tilt compensated compass module. I also have an older LS-40EB-3V GPS Module to add to the mix; hopefully I’ll have some ability to navigate my way about.

Link: http://picaxe.multiply.com/photos/album/16/Twin_Cab_Tracked_Vehicle
 
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