Think I will get it more complete before giving it its official name.
So far have completed its jaw weapon except for a couple of mounts for the dual actuators. Picked up some 3/8 roller chain and sprockets yesterday and have settled for a reduction of 3.33:1. Have discarded using angle grinders and it will be chain driven throughout. Will soon order a couple of the 300 watt scooter motors and run twin chains off each motor. The stats tell me that at max power this thing should move at around at 20kmh or more. Will be interesting to see the results, theory and practise dont always agree but as long as it doesnt stall too much it should be ok, i hope.
At stage of designing the drivetrain mounts and support structure. Will be making it like Pinscher in that the left and right side section will be built seperate from the weapon and the three sections welded together at the end. Originally thought I would make a rollcage first then put everything inside but found the other way will work best for this layout.
STill have to decide on a second weapon or armour/batteries.
Will come a day when spinners will be lightweight so have to be prepared, very prepared.
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Last edited by Nexus on Tue Dec 20, 2005 2:22 pm; edited 2 times in total

Picked up some 250 watt scooter motors today so have reasssebled my POP into its latest structure around the almost complete jaw assembly.

Have decided to go with original plan and put a motor on each wheel.
Second weapon has gone to the back of the list and drivetrain fisrt.
Probably will run it at 24volts as unloaded the rpm to the wheel is 795, and thats on a 150mm wheel.
What s the formula for working out speed in kmh anyone?
get a result but figure there must be a real easy formula.

THis unexpected decision to go scooter has forced a rethink of a few things, mainly because these motors are 100mm high.
At this point starting to forget the robot this is based on and start building with what i have got.

One thing thats going to be different is that the back wheels are going to be closer together than the front. It gives it a more appropriate shape for its wolf qualities and should help reduce some drag on skid steering.

An unexpected hurdle was the size of the sprocket to turn the wheel. With the chain on its 100mm high so its hard to include it in a rollcage with a 120mm height so chains will be exposed at places but strategically placed armour might have to be worked on down the track.
Have been stuck on how to deal with the chains for a while but think have worked it out.
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motor rpm x 60 x ( 3.14 x (wheel diametre^2) / 4) = kph

This works as long as the wheel diametre is measured in metres

THanks for the formula but cant seem to get it to work.
Maybe i am squaring insted of square rooting, cant remember but seem to end up with speeds near mach1 so must be doing something wrong.

With a piece of string and a ruler i estimate max top speed around 22kph.
Would someone mind processing my figures to confirm that.
795 rpm x 150mm wheel = ???????kph
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I think the formula would be

RPM x 60 = Revs per hour

795 x 60 = 47700 RPH

Circumference = PI x Diameter OR PI x 2 x Radius

So 150mm x 3.142 = 471mm OR 0.471 metres (feels about right)

and RPH x 0.471 = 22466.7 metres per hour OR 22.4 kph

Your right George, keep that string
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I am a goose, I used area instead of diamtre, sorry for any inconvienience

Thanks for reply anyway, made me feel better that I wasnt the only one that stumbles on simple formulas.

Yesterday took a grinder to King Pins jaws to remove metal to allow the actuators to move in. Made some progress as have been thinking about the mechanics of it.

Started off looking for formulas for this to but somethings are easier to just pick up and move with your hands to see if they fit.

Will be combining 2 different actuators in one. Car seat actuators are very slow but fit like a glove so due to a missing part and limiited travel will be replacing the screw part of it with one of Garys super actuator screws, (Works very well on Pinscher).

Just realised that the Actuator on Pinscher has a larger groove meaning its like a gear in that it will increase speed by at least 60% so on the Seat actuators its a big plus.

Am also going to offset the mount point of the actuators on the jaw to increase speed as well as reduce the lengh of the actuator arm to also increase speed so it shuld all help but never intended for this to be as fast as Pinsch, it will be more controlled and articulated having 2 seperate mechanisms to control.

Almost at point of cutting the actuators to length, have some tweaking to do as the issue at the moment is at full lift the top jaw will press on its motor, very bad. So trying to cut it to ideal length where actuator bottoms out on its screw just before it wants to touch the motor.

Limit switches are an option but trying to use minimal parts for maximum range.

Have finally worked out how to mount the scooter motors. Will be mounting them Mount to mount so they share the same screws and that will allow you to remove and adjust motors and chain tension on 2 motors with the same 4 screws. This also means less metal required for the frame. ONly minus is that I will have to remove the threads of 2 of the scooter motors base to allow this to work but it seems like a small cost.

Last point is that looks like I will be scraping in to make weight.
THought it would weigh less but
2 x 12kg Pinschers = 1 x 25kg King Pinscher it seems.
NO second weapon but the 6 motors will be a handful anyway i am sure.
Really wanted 8 but.
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Not much actual work done but the POP is slowly evolving.
Sometimes not having funds to blow forces you to think of ideas instead.

Picked up a couple of tyres/tubes today so guess have decided to give up on 150mm wheels and settle on 200mm.

They are wheelchairs tyres so they have a tread similar to a racer and are grey, coincidently thats the type Team Mutant robots use which is my biggest influence. THink they will work a treat.

Have to find some cheap trolleys from supercheap or somewhere to find steel rims for them.

Its going to free up some room so its going to make things easier and give it a higher ground clearance. 100mm motors with 200mm wheels makes it easier to work with.

As each part is decided on it sort of starts to be a bit different that the robot I am basing this on. Main difference is that it will have a neck which is bad in some ways but will look more interesting.
My top speed will go up now as well so hoping my gear ratio gamble works.

Last few things to work out are rims, connecting them with sprockets and then bearings. Hard to make a desision on any until standard sizes are sought, mainly the actual shaft diameter to hold the rims, then match that with a bearing system.
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JUst uploaded some pics, hope they work.
http://robowars.org/forum/album_pic.php?pic_id=211
http://robowars.org/forum/album_pic.php?pic_id=212

Almost ready to get into some building as have had lots of choices to decide on. How many motors? what size motors?.
Am starting to wonder how much heavier this bot would be than a feather as at the moment theres a slim chance a variation of this bot could be a feather so will be building it very minimalistic.

This design doesnt need much armour as the wheels will always get hit first.
Will be mounting the motors and drive train on a 6mm ali floorpan and bolting this to the weapon like on Pinscher.

Have designed a bracket which will let me change motors so I could run either size scooter motor and change them easy.

THis robot will have multipe options which should mean in some configs it will be a lightweight and in others a feather.

Some of its variations:
Motors and actuators can be removed from jaws turning front end into a ramming wedge thats also invertible and pivots sep from body so it cant get flipped from the front.
Rear wheels can be removed and a thwacking tail put on to actually do some damage.

Always liked the idea of jaws out front and wacking tail out back. Makes it more organic like a dinosaur and dont think I have seen that combination of weapons before. Should actually be able to do some damage before moving the jaws in.
THis would be a fighting setup because when at home it will always have 4 wheels.
Other options will come up, like a hammer mech but will do the drive first.

So to sum up, having too many choices has led me to design it to be modular and expandable and have the option of making it hopefully work in 2 weight classes. As a Lightweight will be designing some shock absorbing armour for the wheels and some form of rear protection as well.
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Hey George, where did u find larger sprockets and teh right chain for thos 7mm pitch sprockets that come with those motors. I was thinking of modifying a small biks sprocket and having a 4:1 reduction using boke parts but if u found a rock solid solution i would love to hear about it.

That looks awesome. the australian donuld hudson is here.
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Details of the sprockets up on another thread but is short gave up trying to find 1/4 inch sprockets and went up tp 3/8. The main sprocket is 52mm thick steel with hardened teeth. Intend to drill 4 holes and mount threads and also use them as wheel hubs as the rest of the wheels are mainly non metallic and shock absorbing.

You will find limited gear ratio possibilities unless u go 2 stage.
4:1 might be diificult to find.
I believe Oatley will be including sprockets and chains in their next update so there might be a solution there but it would be the scooter ratios I would guess.

Have lots of bike parts myself that I intended on using but chains from racers are designed to slide off the sprocket so was looking at bmx parts for a while also.

Am trying to make it rock solid so the bigger chain will transfer lots of power.
My Ratio is 3.333:1 but the 1/4 inch chain would give you a bigger reduction in the same size sprockets but it would be closer to 6 or 5.5:1
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quote:

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Originally posted by Nexus:
My Ratio is 3.333:1 but the 1/4 inch chain would give you a bigger reduction in the same size sprockets but it would be closer to 6 or 5.5:1

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You re absolutely right but changing the pitch lets you use a smaller drive gear with less teeth which will alter your ratio.

The large sprocket is about the same size but at 1/4 inch it has over 80 teeth and at 3/8 it has 30 so what I meant was in physical terms it doesnt make much difference because any variation is on the motor shaft.

My settup is based on the smallest and largest gears to get the biggest ratio I can but the hgher ratio is achievable in literally the same space with 1/4 inch.
Scooters are 5.5:1.
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Heres a better pic of the chain setup.
http://robowars.org/forum/album_pic.php?pic_id=213

The clamps holding the bearings are just hose clamps out of Pinscher. Used those to hold the front of the drill motors with but they are just being used as a guide.

The problem I face and not many others do is that my wheels can only be supported on one side needing lots of support.

The most expensive part is the larger sprocket at $10.00.
The chain is at its minimum length which doesnt give much room for bearing mounts, prob have to add a couple of links with some setups.

Idea is to end up with easy to service and replace parts.
Am also trying to work the drivetrain into the weapon mounts to end up with a simple, clean and strong frame design.

Large sprockets will eventually have a stud pattern matching a common size wheel.

Still playing with the idea so welcome all suggestions. Cant afford 8 pillowblocks at the moment and dont know if i can justify that much money on mounts so looking for alternative solutions.

Hose clamps might work if you use enough of them but when u tighten them it puts too much strain on the outer bearing case and creates friction so dont know yet but.
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Had a bit of luck today finding parts on the net.

Firstly after an effort, have finally got through to someone in the states in regard to 6 inch pneumatic wheels, woohoo, cant wait, they will give me my stud pattern and also the smallest pneumatic wheels in Oz as they simply dont exist in this country, woohoo.

The pneumatic wheels are for non combat fun as this robot will be all terrain as I have a few plans for it.
I will have my own version of battletreads for saws and spinners and will be able to change wheels easy enough.

And have found a local supplier that has pressed steel bearing housings which i have ordered some and will match them with bearings from a local supplier. Will work out a fair bit cheaper than buying a complete solution from rcm.

Its coming together with these parts on the way, not much left to find, a 1/2inch shaft, some bearings and nuts and bolts.
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