today's work

[Davidh]

Hello David,

Thankyou for the feedback on your gearbox component suppliers. Once again I have a few more questions if you don’t mind.

I am thinking of producing a cylinder design and going down the path that you have pioneered and prototyping all components in Renshape. I am confident I can do this. Then I will make silicon moulds and produce a few. I would eventually like to produce a single shaft and twin shaft endcap.

I have been reading and re-reading anything you have written up about endcap design. I have particularly been looking at your drawings and diagrams. They tell me heaps.

I have spent a couple of hours going over the suppliers websites that you referred to me, Thankyou. However here are the questions, they are rather specific, I hope you don’t mind...

Do you have the actual parts numbers for the spur gears you use, the pinions on the motors and also the cup seals you employ?.

I noticed that you had a bag of seals and oilite bushings, When I was looking at the various suppliers they only seemed to quote for a couple of seals or oilite bushings each. You obviously get a bulk order. May I ask what is a realistic price per unit both seal and bushing?

It is hard for me to gauge how much friction should be imposed on the shaft by the cup seal. As you know I have built my own cylinders and have used seals but don’t know where that threshold is. It is probably something hard to explain. Do you have any wisdom on this?

I have had to think through conversions with inches and millimeters.

Hope you and Ellie had a nice Christmas.

Thanks once again
David H from Oz.

[Subculture]

I see you're going for a sensorless brushless rig, what esc are you going to use?

[RCSubGuy]

For now, and until we find a better solution, we're sticking with Mtroniks producs. Great ESC's, but pricey.

[Subculture]

There is a cheaper alternative, which also gives you the best in brushless esc tech e.g. excellent start up smooth throttle response etc. Cost for controllers is typically between $5-20 depending on current and voltage range, but for scale sub use the lower range of cost is applicable. BLheli multicopter ESC's, they can be used in bidirectional mode, just has to be set-up in a cheap downloadable app. Once configured you don't have to touch them again.

BLheliS firmware esc's tend to be cheaper than BLheli32, the former is open source with the latter closed and a license fee applies.BLheli32 offers some extra features, and uses the most advanced microcontrollers, but BLheliS is really good and more than adequate for sub use.

[trout]

I looked at the BLheli escs, cost is great, just need to play with them. Bob did you match them with what motor?

[He Who Shall Not Be Named]

We’re familiar with the trick of bending a straight piece of plastic or soft metal rod, be it square, hexagonal, or other cross-section shape. You just pinch the rod between thumb and forefinger, and pull through with the other hand at an angle and so doing impart a constant radius curve to the rod; the more radical the angle, the tighter the radius. I wanted to fatten the flange on one of the masters and required a ‘circle’ of styrene strip that would be bonded to the existing flange.

To keep the wide strip from twisting away from the desired curl I pulled it through a circular channel cut into a big wooden dowel. Three passes of the plastic strip and I had the circle required, which was then super glued to the flange, building it up to the desired thickness.

Clamps held the circular piece of strip to the flange as I applied the glue. As the added strip was a bit bigger in diameter than needed, I trimmed it back on the lathe.









I spent the afternoon getting the modular SubDriver bulkheads, and gear-splitter masters ready for tool making. Some putty work, sanding, and setting each master in a clay backing.





The clay creating the separation plane between the eventual two halves of the rubber tool used to make the cast resin parts. The face of the masking clay dimpled to form a network of registration keys in the rubber that would insure proper alignment of the tool halves. Containments (flasks) of Lexan cylinder and masking tape would hold the catalyzed rubber as it cured from liquid to solid.

[george]

Do these larger pieces that you are creating rubber molds of still also go into the pressure pot and because of their size and amount of rubber is their time in the pot longer? Is there any change in the amount of air pressure applied?
Thanks for the continued lessons.

[He Who Shall Not Be Named]

Do these larger pieces that you are creating rubber molds of still also go into the pressure pot and because of their size and amount of rubber is their time in the pot longer? Is there any change in the amount of air pressure applied?
Thanks for the continued lessons.

Yes, the eventual tool will be filled with resin then placed into a pressure pot and taken to between 15-30 psig, just like any other pressure-cast item.

David

[Subculture]

With regards to brushless esc matching, I simply go by the current the motor is likely to draw in the install under peak and average loads. I rarely feel the need to go beyond 20A, which is good figure in terms of price top performance. However most hobby grade brushless motors can pop an esc under stall conditions. if this is a concern I would look at BLheli32 as they have a current limiting feature, which prevents the controller getting cooked if extreme loads are pulled either through a stall or a short circuit post output on the controller.

Full set-up guide for BLheli32. Probably more than most want to know, but these esc's are very feature rich.

[RCSubGuy]

Andy, this is looking really good. I'm going to order some to play with this morning. Thanks for much for the info!

[Subculture]

Good stuff, You will need a small USB dongle/widget to program them, I use the Afro USB dongle which I got from Hobbyking. They only cost a couple of pounds. I've used Little bee esc's with blheli16 which are well regarded, can't give a recommendation on blheli32 yet, as I haven't used one. Plenty of choice on places like Banggood, Hobbyking etc.

Anyway, I won't say any more on the subject as its rather hijacking Dave's original thread, perhaps move it to a dedicated post if you want more discussion.

[He Who Shall Not Be Named]

Good stuff, You will need a small USB dongle/widget to program them, I use the Afro USB dongle which I got from Hobbyking. They only cost a couple of pounds. I've used Little bee esc's with blheli16 which are well regarded, can't give a recommendation on blheli32 yet, as I haven't used one. Plenty of choice on places like Banggood, Hobbyking etc.

Anyway, I won't say any more on the subject as its rather hijacking Dave's original thread, perhaps move it to a dedicated post if you want more discussion.

Highjack?! …. **** no! This is just the sort of good, authoritative stuff I want smeared all over this site, Andy. Keep pumping it out, pal.

If someone steps on my toes, you can be assured they will be 'informed' of my displeasure, and suffer my wrath!

David

[Subculture]

Well the afro usb link tool no longer seems to be available from HK, however equivalents are available on ebay etc. Another less expensive way is to use an Arduino Nano board. As these are fully programmable they should totally flexible and can move with the times e.g.

[gantu]

Yes Udo use also the blheli_32 wax’s only the 51a version and the software blheli_32 .

https://hobbyking.com/de_de/turnigy-multistar-32bit-51a-race-spec-esc-2-6s-opto.html

[gantu]

See this perfect working.