4WD Front Hinge Flipper - Featherweight

[dotDominic]

Updates to be made! Just got back from the Gloucester event - brought along V1 again which I used to test out several of the parts and design tweaks I'll be using in the new build. For 6 fights of the event I ran the machine on the two small 4 Cell 15.2V LiHV packs in parallel, and the 12v argos drills handled it with no problems at all. I think the machine was a bit faster and more powerful - it's quite hard to tell the difference when the arena is so big and I'm only upping the voltage a little bit. The new front wedge was also low enough to get under Explosion and Heatwave once or twice - the old one was hopeless and I would always lose wedge vs wedge contests. Was still a bit too steep to reliably get under robots easily, and it still seems to lose all most of its traction when upside down, but overall the robot was the best it's ever been, so things are looking up for this new build!

A few changes to the flipper setup - Will still try the 1500kv Outlander motor, but I've changed the actuator for a HIWIN 18v one as on ebay they were half the price of the gimson 12v actuators and seem more robust, whilst being roughly the same weight, speed and also having very similar dimensions. (I think it's the same model as Aegis?)

Also some tweaks to the CAD to cut down weight in some areas and beef up the armour in others. Flipper panel + hinge mounts are one piece of bent hardox and there is now a small sloped 15-10 mm HDPE lid. Wedge and flipper are now 4mm hardox, sides are 20mm HDPE, and the rear is 15mm. Side panels are now also bolted to the inner bulkheads at the front as well, rather than just the middle. Great suggestions with the polycarb, but I think I'll be keeping the wheels exposed or else the robot will look quite similar to the new Rapid/Astro.

Strix CAD Ver 3.png

Had a quick ask around at Gloucester what people thought of potential robot names. At the moment I think Strix has quite a good ring - it's a vicious bird from classical mythology that was a sign of bad omens.

[Maxamuslead]

Strix has quite a good ring - it's a vicious bird from classical mythology that was a sign of bad omens.

Bad Omens to whom =P If you do call it Strix, Stick a owl on it.

[dotDominic]

Haha, providing all goes well it will hopefully be a bad omen for the other bots I fight! I do plan to use some sort of bird graphics but could always take that a step further!

[dotDominic]

So a quick post as I haven't updated this in a while:

The Hardox flipper and wedge arrived today and seem really hefty - I was a bit cautious about my weight calculations but they've turned out pretty much spot on here so that's a huge relief.

IMG_4105.jpg

Also mounted the brushless motor to the actuator and flashed the ESC so it will run in both directions. (Big thanks to Rory for the guide in his build diary) The weapon system should be up and running soon, once a few more bits and pieces arrive in the mail.

Progress has been a bit slow the past few months, but I'm hoping to kick things into high gear now I have these Hardox parts.

[Maxamuslead]

Is that Hardox all folded ? if you don't me asking but how much did that set you back ?

[dotDominic]

Yeah it's all folded - nah man I don't mind at all.
Without the VAT the wedge was about £40 and the flipper £60. It's a lot of money, but I don't think it's that expensive considering what it is. I mean this is pretty heavy duty stuff and it's almost exactly to my specs - except maybe a few mms here and there, and also the corners of the wedge. But that's mostly due to how the metal behaves when folded + a lack in my understanding of relevant calculations. No big deal though, will be able to tweak it.

[Maxamuslead]

i take it, it was kcut that you used ?

[dotDominic]

Yeah I used KCut. Pretty sure they are the go-to for this.

[Shooty]

Machine is looking really good, I'm excited to see the linac in action!

[dotDominic]

So it's update time and I finally got the actuator going - It really worked

...

For about 10 minutes, then it broke itself.

I've got a quick, badly-filmed video here which shows it running on 5s with a low throttle setting:

Rory's Arduino sketch deliberately reduces the power/speed of the motor, but this can be changed to give more power (Big thanks to him and his really useful video + easy to follow Arduino sketch). So I thought it would be a great idea to increase the power a bit, and then it broke. Interestingly it still wasn't anywhere near full power though - I think I only increased it by about 25%.

However! There is a morsel of good news! The motor did stall for a short while, and the gears + the threaded rod are all absolutely fine. I'm not entirely sure what the problem is - I suspect the failure lies on this soft plastic piece which travels up and down the barrel of the actuator, and pushes out the steel rod. Right now it can travel forwards/outwards, but this plastic piece does not want to go backwards/retract along the threaded rod and down the barrel. I think if I could replace this part with some sort of the metal threaded fitting, then this would really work. So I'm not beaten yet! I'll do an autopsy to try and see what the problem is - unfortunately I can't get this plastic piece out, perhaps because it is damaged, so this may involve cutting the end of the barrel off, but I will see.

EDIT: Looking back, it's not as slow on the lower setting as I remember. If cranking up the power really doesn't work out then I might just use the motor as I did in the video.

[R9000]

Yep! This happened to me too (albeit before I put the limit switches in). That plastic acme nut that slides up and down the barrel is way too soft, and basically it shoots off the end of the screw, obliterates the plastic washer at the top, and then cross-threads itself when you try to wind it back down. On Aegis I put a metal washer on the end of the screw to stop it happening again, plus the extra load of the scoop stops it going too crazy. Thing is when I tried to get a spare part, I couldn't find anyone wanting to sell me anything less than the whole actuator for more than £100. But if we can figure out the pitch and diameter of that acme thread, it shouldn't be too hard to make an aluminium or even steel nut for heavy-duty operation. Until then, you might have to try and find another actuator. :/

[dotDominic]

It's funny you should say that Rory, because I do actually have a spare actuator of the same model. I'll sacrifice my damaged one for the good of roboteer actuator modding - take a hacksaw to it and look at the dimensions of this threaded rod. There is a part in the gearbox which seems to stop the rod from slipping out, but even with heat it seems almost impossible to remove. With my tools I think this is the only way of properly opening this thing up.
If it means more powerful actuators, then I'm all for using metal parts to replace these plastic ones.

[dotDominic]

So it's update time again - after taking a look at the broken actuator, I actually think that this is a non standard thread. I have tried a few nuts on this rod and neither fit. There are many other problems with this stock actuator too, so I suspect I will end up spending even more time faffing about, trying to replace parts with lots of trial and error. So with the help of a friend, I have decided to have a shot at something a bit different - building my own "super actuator" from scratch!
Here is the CAD:

VenatorRobotics-TeamImpact Super Actuator.jpg Super Actuator 2.jpg Super Actuator 3.jpg Super Actuator 4.jpg

My design uses most of the stock gears and keeps the same ratio as they stood up perfectly fine to the power I was putting through them. I have an extra set of gears from my spare actuator if they do break at some point. Everything else will be new parts, which will hopefully have these advantages:

• Easier to disassemble if something becomes damaged and needs to be replaced. Many parts of the stock actuator are very difficult/impossible to remove without damaging the components. Most of the new design is bolted together and easy to take apart.

• Sturdier Limit switches. The inner barrel dimensions of the stock actuator are designed specifically for some pretty small limit switches, which seem too fragile for what I want. The way they are mounted also meant that they didn't activate properly when I tested them with a fast motor. On this new design, the switches are mounted to the rod which moves in and out, and they are activated by being pressed against the cut outs in the barrel. So there is no way that the rod can reach the end of its travel without the switch being activated.

• Metal Acme Nut. A metal acme nut will be welded to the inside of the moving rod. There will be another welded to the end of the threaded rod to stop the actuator at the end of its travel. This will be much sturdier than the soft plastic which failed in my tests.

• I can make the actuator with the exact amount of travel I want, I'm not just restricted to standard 50mm, 100mm etc sizes.

• I can use much more of the brushless motor's power/speed than with the stock actuator.

Admittedly it would probably be more effective to use a brushless motor with a large gear ratio, similar to Amnesia. However, that's already been done and I want to build something a bit different - plus I think an actuator looks cooler. This will be a bit of a challenge for me, but hopefully I can make it work!

[R9000]

Can't wait to see how this turns out - I might have to make my own for Aegis if it goes well!

[dotDominic]

Thanks! If all goes to plan then this should be a bit of a beast!