For those considering gears......
As I stated above, the need for gears in FE is, for the most part, just a distant memory. Yet, there may come a time when gears are the best options, especially when dealing with these really little boats where motor choices are limited, or there are physical space limitations.
Over the years, I've collected a bunch of gears and geardrive assemblies; the latter mainly for aircraft applications. For the most part, you can find slot car and RC car gears that will work in the little single-stepper I'm presenting here or similar-sized applications. The Hughey gears were bullet-proof nylon with metal hubs and had a pitch (pitch ratio) of 32. They were quite large in comparison to what I'm using here. Slot cars most often use 48 pitch gears with the occasional 64 pitch. In all the gearbox photos I attached above, I used 64 pitch gears from slot car applications and from SDP/SI.
But that was then.... :glare: Now enter Metric Pitch gears. :olleyes: I am going to use 0.4 Module (the metric measurement standard instead of pitch) in this application; but here's what I discovered: 0.4M gears are REALLY CLOSE, but not exactly like 64 pitch gears. 0.5M (0.6M?? :confused2:) gears are REALLY CLOSE, but not exactly like 48 pitch gears. You could probably run a Metric/Imperial gear train for several minutes before you ground all the teeth off. :crying:
So take heed my friends; pay close attention to any gear set you plan to use; make certain your pitches are right.
Good News, Bad News, Success, Failure......
It was smooth water on the lake! :banana:
Well, the first one I threw in the water for testing was Prototype #2 "Homie". Homie has the 3300Kv inrunner that started this whole single-step hydro endeavor when it seemed to work so well in that first hull even though it was so bulky.
I put Homie in the water, goosed the throttle, and promptly broke the driveline,thereby rendering it useless for further testing and sending a brand-new prop to the bottom of the lake. :cursing:
I thought I'd go right to Prototype #4 next, seeing as it was the result of my more recent ideas. Thinking I may have excess power available, I ran the first bit at partial throttle. I found a throttle setting where it ran extremely well with a perfect attitude and was capable of nice, tight turns. It would tend to lean towards the outside of the turn and I think an angled turn fin would help that as it would want to dig the inside edge of the hull downward as opposed to lifting as it was with the straight fin on the hull (I just used the fin from the original prototype hull). So far so good. Now, it's time to open 'er up!
I wait until it is coming at me (so it's closer to shore and I don't have to go so far to retrieve it if something goes wrong) and hit the throttle.........
It all happened so fast, I don't recall the exact sequence. :scared: First, it hauled @$$, then there was some flying, some torque rolls, some swimming around underwater looking like a fish, and surfacing somewhat reminiscent of that submarine-based launch of a Trident missile that everyone has seen on TV at some time. :huh: I learned to drive it after a while and could do OK, but given the available power (and the urge to use it.. :olleyes:), it was for the most part uncontrollable. It's own wake from an earlier lap was enough to launch it or send it in a emergency submarine dive depending on the magnitude and orientation of the wake and your speed.
I did manage to do some CG testing, and it was much better with the CG moved forward.
In my playing around with #4, I noticed it was real torque-sensitive. I might attribute that to the outrunner motor. All those big, heavy (relative) magnets spinning in a large (relative) radius IS going to have an impact.
All of this makes me think the little geared motor concept may actually be the ticket for this hull. I am currently using a 1000mah battery, and since I want to move the CG forward, I may go with a considerably smaller battery since the geared motor arrangement will draw less current (lower total Watts). This kills two birds with one stone: Improved CG and lower overall weight.
Oh yeah, the last bummer. There was no one there that could take videos...... Next time out I may have Prototype #5, the geared one, ready to go. :Praying:
What to do while I'm waiting for parts to arrive
The first MPR ran pretty good with the finned 2030 motor (3300Kv), although the bulk of the hull was a big impediment to going fast. The little outrunners (3500Kv) proved to have too much torque and seriously overpowered the hull. They will find a new home somewhere in another of my hare-brained schemes.... :olleyes:
I think I will retire Prototype #2 (Homie), and transplant his little inrunner into Prototype #5. I'll also remove the straight CF turn fin and make a new, angled one from aluminum sheet.
In addition to the single-step hydro project, I'm also repairing/updating hulls that needed work before the next time out. While I'm waiting for parts to show up, I've made repairs to the 1:20 Atlas prototype (broke a driveshaft on a loose fishing line :cursing:) so it will be ready for additional prop testing the next time out. The 1:20 Short Circuit encountered some "Hangar Rash" :mad: and should be repaired within a few days (have to wait for paint to dry). I'll use the Atlas Prototype to find a prop that works well with that motor/battery combo and use the same thing on the Short Circuit for starters. I made some "Quick and dirty" strakes from PVC sheet and glued them to the bottom of the 16" Cat, so that will be ready to test the next time out as well. Stand by to see some posting in that thread too.
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The Disadvantage of Inexpensive Boats.....
They (or the necessary parts to make one) often come on a slow boat from China..... :(
Another Thing I Noticed.....
When tearing the outrunner motor out of #4, I noticed the heat-shrink wrapper on the ESC had melted. For most of my minis, I use that cheap 30A ESC that can often be found for under $5 (See: https://www.ebay.com/itm/New-HW30A-B...r/392519751649). The problem is, it's rather large for this hull, so I used its little brother, the 10A ESC in all the single-steppers.
Normal running on the surface was fine for the ESC, and this makes sense as only half the prop is in the water, thereby reducing the overall load on the motor. The problem was when it was swimming around underwater like a fish; for a LONG time. It did this in full "Knife-edge" and with the partial loss of radio, it went to full throttle with an entirely submerged prop. :scared: I think that's when it was drawing enough current to melt the shrink-tube. The water in the lake was really clear and I could watch the entire aquabatic demonstration. Fortunately, after everything was done, there wasn't a single drop of water inside. :cool2:
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All I Need is Paint and Batteries....
.... And I HAVE the paint. Or at least the primer. :wink:
I decided to go with a smaller battery which will cut 36 grams off the total weigh as compared to the 1000mah cells in the other hulls. Deduct about the same amount of weight for the much smaller motor and this boat could conceivably be 25% lighter than the other prototypes. :w00t:
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It's About Time to Clear Things Up....
..... And I'll shoot a couple of coats after the base coats and decals have had a few days to cure.
I may call this one "Goldbrick". :spy::lol::tt2::olleyes: