My first beetle weight, just some questions

Hi guys

firstly i must say, great forum!

i have looked into what i want to build, im thinking about a fast, ram-bot type deal, with scope for making it a lifter, i thought about a spinner but for safety sake thought against it,

for the motors i was thinking about

http://www.technobotsonline.com/re-2...rbox-15-1.html
2 of these,

http://www.technobotsonline.com/sabe...er-for-rc.html
this as the esc, although im wondering if it is a bit overkill

banebots wheels, hubs, e.t.c.

Aluminium for the armour, i have a box of sheets so this would be preferable.

can anyone recommend a cheap as chips 3 channel rx and tx?

also what battery systems would you guys recommend,

thanks!

Hi Tom,
Those motors are only 1.5-3v, not really good enough for our use. A couple of us, myself and Dave Weston used the 12-24v versions of those motors and found them really quite lacking. Changed up to these which seem very popular with Australians and US Builders. I like em too. http://www.ebay.co.uk/itm/2-x-12V-DC...item4d02562621

That esc will work, but I don't much like them, just preference. Many use them to great effect. There are cheaper alternatives if you are interested. Won't be quite as plug and play as the sabertooth.

Aluminium could work, depending on thickness and grade.

3 channel.. do you mean a minimum of 3 channels, or like a pistol grip type transmitter or just stick radio with 3 channels?

Either way, hobbyking and giantshark have cheap 2.4ghz radios, although I think its a good idea to get a fairly decent radio from the off.

Look at 2-4 cell lithium polymer batteries I'd say.

Cheers. Harry.

just a quick note about the sabertooth, i use 1 in my 4wd beetle and it seems to work fine but if your using a high torque servo you will need to disconnect the BEC and add an external or it will either stop when the servo is used (and stay there until you turn the power off and on again) or drive off and the error light will flash on the sabertooth esc but otherwise mine drives it quite nicely

@harry

thanks for the quick reply!

what esc's would you recommend over the saberooth, all of my knowledge so far has been some minor research!

i may get the giantshark one, im on a fairly lean budget for the electronics,

i will definitely be getting a set of those motors, they seem like awesome pieces of kit,
do they need some kind of gearbox, or can they be directly mounted to the motor?

also the aluminium truth be told i picked a load up at a jumble sale, the guy couldn't ive me any more than that unfortunately!
if not i will look into some 4mm nylon, or thicker!

Look at Botbitz esc's. I've got some 10a ones, pretty good. You need two as they are single channel.

With plastics you'll want to go quite thick, say 10mm or so. I used 12mm nylon as a frame on my last one.

How thick is the mystery aluminium?

1.5-2mm thick, imagine the front of a synth or amplifier,

they seem competitive, may pick up a set

what about the gearbox conundrum with the motors?

thanks

I don't think that's really thick enough mate, and it being an unknown (at a guess fairly soft) grade I can't seeing it be much use.

Gearbox conundrum?

can i directly mount the wheels to the motors?

fair enough, although i may use it as a baseplate to mount motors too, until i can sort out some acrylic of nylon

and will i need bearing blocks to mount the motors, or is it worth machining my own mounts?

Both the MFA motors and the motors I linked have gearboxes and so you can mount wheels to those easily, banebots if you like or similar.

Don't use acrylic, it shatters. Nylon, HDPE, polycarbonate are more usable plastics.

so as a guide for prices,

15 for the motors,
30 for the esc's
20 for the radio system
15 for the battery
10 for wheels
10 for the hdpe sheet
5 for miscellaneous
£105, does this sound reasonable or is that a dreamy figure?

also does hdpe need to be thicker?
is it resistant to spinners?
by the looks of things it will be quite a fast bot, i will get the parts ordered tomorrow, including silly imperial allen keys for the hubs :p

Link to each part, then we can all make sure that you're not going to make any mistakes etc. Don't forget to include postage and customs etc

£150-170 is probably a more accurate figure.

http://www.ebay.co.uk/itm/2-x-12V-DC...item4d02562621

http://www.botbitz.com/index.php?rou...&product_id=56

http://hobbyking.com/hobbyking/store...arehouse_.html

http://www.directplasticsonline.co.u.../Natural/10mm/

http://www.technobotsonline.com/bane...-shore-30.html
have the hubs

ignoring the rx and tx, have i missed anything?

Battery charger? Also if I was you I'd get a high power servo from hobbyking in case you want to add a lifter as the postage will probably be more than the cost of the servo if you order it separately- but that's your choice.
If you don't already have them you need a connector for your battery and a removable link/ switch or something (I'm not sure on the beetleweight rules for this).
Other than that it looks like you've got everything.

ok how many mha should i aim for?

and what thread are the mounting bolts on the front of those motors?

also it doesn't say on the botbitz website if they have a BEC for the Rx?

will these do for the battery and the charger?

http://www.giantshark.co.uk/product/...c-lipo-battery

http://www.giantshark.co.uk/product/...harging-system

thanks in advance!

BEC for the Rx? YES they have

thanks a lot for all the help guys now i need to go and get some cash :p

What is the best way of mounting those motors? I was thinking a hope mounting hole and some kind of clamp or just making a plate to mount he front of the motor to, will that be strong enough?

http://www.youtube.com/watch?v=c_j0W1cAKOA
Is how I made mine

i just used a bit of 2mm aluminium u channel to mount my 4 motors but you can buy ready made brackets off ebay and amazon

http://www.amazon.co.uk/Pololu-Metal...eywords=Pololu

http://www.ebay.co.uk/itm/2-pcs-Stee...item417753aa06

http://www.ebay.co.uk/itm/25mm-Motor...item33781e0245

I think I'm going to make one out if the 10mm hdpe sheet I have orders, to mount things to the top and bottom, can I thread it or will it be too soft, or are there wallplug type things I can get I can get?

I wouldn't go any smaller than m4, or any bigger than m6, into 10mm HDPE. My beetle, Gonzales, is put together with m4 bolts into the 10mm HDPE. The joints feel pretty strong. Do be careful to not cross-thread, though, put a bolt in an already threaded hole badly and it'll never hold a decent thread again. I only start holes with a tap, then let the bolt form its own thread into the rest of the hole. The result is satisfying enough.

For the record, it is considered fairly bad practice to thread HDPE with bolts, although in my experience it does work. Woodscrews (or any coarse threaded screw) will hold nicely in HDPE, but the strength of the join will weaken the more you take the screw in and out, like in wood.

There are push-in inserts which are rough on the outside, and are tapped to a metric thread on the inside, which are kind of a happy medium. They can be pulled out, but I don't know how easily, never used them. Another kind, which I'd expect to be pretty sturdy, is this sort of thing: http://www.ebay.co.uk/itm/M4-x-15mm-...item4175771d12 - might experiment with these sometime, I imagine they're good into thick enough material (10mm might be on the edge).

Another method is the bed-bolt style, also known as barrelnuts: http://www.finewoodworking.com/uploa...olts-01_lg.jpg - these involve some quite fine aligning, but done right they're probably the sturdiest method of attaching things to plastic. Used these for the entire construction of our featherweight, and a bit in the beetle mentioned above, and they are very strong. I don't seem to see them smaller than for m6 bolts, though. I made some m4 ones for my beetle.

Those inserts look great for attaching a top plate I may just wing it for my first bot and try the first method with a reinforcing block along the inside as it is going to be more or less rectangular so I can make it quite strong!

Hi guys, whats the best way to cut hdpe? i have a jigsaw at my disposal and a wood saw, which would you recommend?

also in the next few days i will start at a build diary

thanks

Both work fine to cut hdpe. I also use a circular saw to good effect though lots of swarf

If using the jigsaw use a course wood blade or else it will clog up.

i did some test cuts and the jigsaw seemed ok, will go with that also what is the delivery time for roughly for botbitz?

ok just about to post a build diary, my stuff has arrived :D