Unnamed FW crusher build diary

[adamclark]

Is there any chance that during a crush and the beak doesn't penetrate then effectively the wedge would drive upwards. Perhaps this would then be using the wheels as the pivot point and you are cracking the drive screws?

[Al_]

The wedge does pick up to the underside of whatever it is crushing but a lot of the weight of that still remains on the ground. I mean it would increase the forces on the wheel axles I think, but I'm guessing by a lot less than if the bot was flipped into the air and landed wheel first for example. I don't think it had much to do with it in this case though, I was only driving it around, not crushing anything at the time.

[lowndsy]

Is there any chance you could drop me a link for the longer LH screws please? I got this spare out of an old dead battery drill, but if I break this one too then I'm out of them.

Sorry, couldn't find the M5 size ones on Amazon any more, but I think this is the same seller on ebay - same location (Germany) with the same flat shipping fee that applies once per order, not item.

http://www.ebay.co.uk/itm/M5-X-30-MM...gAAOSwuxFYz9Z5

They do a 35mm length version too

[Roboteernat]

Sorry, couldn't find the M5 size ones on Amazon any more, but I think this is the same seller on ebay - same location (Germany) with the same flat shipping fee that applies once per order, not item.

http://www.ebay.co.uk/itm/M5-X-30-MM...gAAOSwuxFYz9Z5

They do a 35mm length version too

There are also these options:
http://www.ebay.co.uk/itm/1-4-Steel-...gAAOSw5cNYZPGa

http://www.ebay.co.uk/itm/4pcs-Genui...kAAOSwo4pYTTIL

and more from those sellers. The amazon seller does not have those screws in stock at the moment - https://www.amazon.co.uk/Left-Lockin.../dp/B003S7U30E

[Al_]

Thank you for all the suggestions regarding the snapped screw. I got to take a good look at the drive on Pressure Point over the weekend to try and figure out the reason for it snapping. The only difference between the 2 sides that I could find was on the side where the screw snapped, there was a bit of debris created from melting the 3/8UNF piece into the wheel. This was stopping the 3/8unf piece from screwing all the way up to the shoulder on the gearbox output shaft by about 1mm. The wheel was still pulled on hard against this, but maybe it was causing the problem. Anyway I have cleaned it up and now it screws on all the way up to the shoulder like the other side, so hopefully this will sort it.

While checking the drive/wheels over, I noticed that I had some odd behaviour going on with the mixing for the drive. I have both channels mixed to the right hand stick on the Tx as I think is pretty normal. The idea being that forwards on the stick gives me forwards on both wheels, backwards gives me backwards on both wheels, left put the LH wheel in reverse and the RH wheel in forwards and so on. For some reason pushing forward on the stick makes the LH wheel turn much harder and faster than the RH wheel which would make the bot turn to the right. In a similar but opposite way, pushing backwards on the stick makes the RH wheel turn much harder and faster than the LH wheel, which would also make the bot go in a curve. However, pushing either left or right on the stick makes the wheels turn at the same rate but in opposite directions as you would expect. Video below to better show what I am trying to explain

I have checked over everything I can think of and I’m fairly sure that the problem lies with how I have the mixing set up as the problem is not specific to just 1 Rx Channel, 1 motor or 1 ESC. I’m running a Spektrum DX6 with a lemon Rx and modded TX85A ESCs, so if anyone has any suggestions I would be very grateful. I’ll add the mixing settings I have on the TX to the post as soon as I can.

Other than the above I have started getting the armour mounted with most of the right hand side done. There are some rough edges to sort and the fixings need a bit of work, but it gives you an idea of the general look.

Pic 1.jpgPic 2.jpg

[Roboteernat]

Just to let you know, im expecting a quote for various length LH M5 screws from our bolt supplier, will let you know when it comes


EDIT The cost of the bolts for 100 25mm, 100 30mm and 100 35mm bolts came to a price of around £1400, as these are usually custom made to order. This was a quote from a very large supplier too. I guess thats the reason they cost so much!

[daveimi]

Have you tried re-binding making sure that the stick is centred and the trims are definitely at 0? The other thing to bear in mind is that a lot of the drills aren't neutral timed, so will take off in a particular direction a bit quicker than in the other. You can rectify this a lot of the time by adjusting the trim at the bottom of the stick a bit to the left/right so it drives straight.

[Al_]

Ah! It never occurred to me about the motors being wound with a bias for operation in one direction. That makes perfect sense, particularly for drills and fits with the symptoms I'm seeing here. I knew it would be something obvious I was missing.

I'll re-bind anyway just to be sure but otherwise just trim it out as best I can and learn to live with it. Thanks David, at lease I can concentrate on finishing it now instead of fixing another problem!

[daveimi]

No worries, I've been in the same boat and just learnt to deal with it lol as much as it drives my ocd insane with having aspergers.

[Roboteernat]

Update on the price for LH screws...

The cost of the bolts for 100 25mm, 100 30mm and 100 35mm bolts came to a price of around £1400, as these are usually custom made to order. This was a quote from a very large supplier too. I guess thats the reason they cost so much!

I am going to get an M5 lh die and machine my own from M6 bolts i think...
Will see if i can do it and maybe have some to sell...

[Maxamuslead]

hell make if you manufacturer at a reasonable cost (and time cost to yourself) i bet some people would buy them.

[Roboteernat]

The LH M5 die is on its way!

[Al_]

£1400 quid? You sure you didn't order them in gold by accident?

I would definitely buy a few if you made them out of a decent grade bolt, anything has got to be better than the cheap Chinese steel that I assume they ones that come with the drill are made of.

[Roboteernat]

I'll put the gold away and machine them from something else 😀

Will give it a go when the die arrives and let you all know

[lowndsy]

I was going to tell the gold joke! I got a couple of spare screws from the German guy, but as a backup for the backup I picked up some lh threaded bar and half height nylock nuts, just in case. Not sure how effective it would be, but it was cheap and might keep me rolling in a pinch.