BMoto Desktop Surfer - with Radio Control??

MADMAT

MADMAT

Location
Ohio
Balduccimoto said:
Video! Pretty sure the reciever got wet again and so it died. It did the same thing last time and it worked after drying out. Pretty good for first water test. It has an aggressive intake so it definitely would rip if I let it run it's course. I let it go on a suicide mission with no hood yesterday and it zipped across the bath tub very quickly before nose diving because lack of flotation.

Click to expand...

Holy chit!!!
 
jo5hi3

jo5hi3

Location
Charlotte NC
I have been playing with rc stuff for a long time, mainly airplanes and helicopters. I was thinking if you needed to drop some weight why not go to a 3 cell, but about half the capacity. That should drop some weight and same a good bit of space.
 
Balduccimoto

Balduccimoto

Location
NYC/Long Island
Mdavies_02 said:
If you dropped the original model, whats the eta to a new prototype? Very excited to see a longer video of a new unit.

Keep up the good work!
Click to expand...

I am moving away from a model that is 100% 3D printed to about 5%. If my calculations are correct, I can reduce the weight from 510g to approximately 350g. This creates alot of new challenges. Just about everything needs to be redesigned. In other words: Optimistically 1 week, but realistically a month.

I did a burn test in the tub earlier with the motor going full throttle for about 5 minutes and the motor became very hot.. Enough to evaporate water rapidly. A little bpipe analogy - another 1/4 turn shut and it would be sizzling! So like I expected - this will need cooling. The good news is that the ESC only got a little warm, therefore I have no plans to include water cooling for the ESC. I have been toying with the idea of a lighter battery that I could drop yet another 40g of weight and keep the same capacity, but discharge ratings are borderline with the motors max current draw. However, those max ratings are the stall current which should never occur. I will have to do some real world testing to see if these batteries are sufficient.
 
Graham Buchan

Graham Buchan

Location
Cold Lake, AB
Balduccimoto said:
I am moving away from a model that is 100% 3D printed to about 5%. If my calculations are correct, I can reduce the weight from 510g to approximately 350g. This creates alot of new challenges. Just about everything needs to be redesigned. In other words: Optimistically 1 week, but realistically a month.

I did a burn test in the tub earlier with the motor going full throttle for about 5 minutes and the motor became very hot.. Enough to evaporate water rapidly. A little bpipe analogy - another 1/4 turn shut and it would be sizzling! So like I expected - this will need cooling. The good news is that the ESC only got a little warm, therefore I have no plans to include water cooling for the ESC. I have been toying with the idea of a lighter battery that I could drop yet another 40g of weight and keep the same capacity, but discharge ratings are borderline with the motors max current draw. However, those max ratings are the stall current which should never occur. I will have to do some real world testing to see if these batteries are sufficient.
Click to expand...

Nice job so far! Do you have a ribbed heat sink on your motor? That will probably help a lot if you don't have it
 
Balduccimoto

Balduccimoto

Location
NYC/Long Island
Graham Buchan said:
So is that just a water sleeve that isn't hooked up?
Click to expand...

Yeah, it slides over the motor with o-rings on each end. Water encapsulates the sleeve of the motor and with my pump design there is ton's of water pressure. Without a doubt the motor will remain frosty. Only reason I didn't have it hooked up is because I didn't have any 4mm tubing available.

If I am right - the weight of the hull with the hood and bulkhead will be ≈ 65g or the weight of 6/10 stick of butter.

Hull 65g
Motor 94g
Battery 54g
Servo 12g
ESC 34g
Reciever 7g
Turn Nozzle 3g

RTR weight is about 300g
 
Balduccimoto

Balduccimoto

Location
NYC/Long Island
What a difference 6mm makes.. I measured water displacement at the top of the bondline earlier and just to be sure I went and measured just below the bondline. It was a difference of 55cm^3.. Therefore a difference of 55g. Although I am down to 320g, I still need to go another 65g. I did a real world test and 250g is perfect where the waterline should be. I can reduce 20g by going with a smaller motor, but there is nowhere else I can lose that weight. I guess that is the reason why all these RC boat replicas have these deep bottom decks is to optimize it's waterline. I really don't want to optimize that way - it takes away from from the scale model's proportionality. I have a crazy idea since I know the components I want to use. I can keep those weights constant, and in excel graph "Scale vs. Surface Area" (weight of carbon lay up) and "Scale vs. Bottom Deck Volume" and optimize between the two to find a perfect scale. One way to predict scale is to ignore increased hull weight:I would need to increase scale by 128% to attain the correct volume. That is a length of 12" long which is a bit larger than I hoped for, but there doesn't seem to be any other way.
 
Balduccimoto

Balduccimoto

Location
NYC/Long Island
It feels like I am updating this alot.. But this has become a journal of a sort. To show the amount of work this entails and maybe find application to a full size jet ski (since the model is like a 'generic' stand up jet ski). I plotted some values in excel by calculating surface area and waterline displacement at various scales. Surface area is assuming a 2mm uniform thickness and water displacement is just below the bondline. Float level is such that the mass of water displaced = the mass of the object. It turns out, as the scale factor is increased the surface area increases linearly while the capacity to float increases exponentionally. In other words, if you were to shrink your hull: for every factor you shrink, that factor had more capacity to float than the previous. No wonder these freestyle hulls sink like a stone :D.

Again, the idea is to keep the model where it still has the same dimensions as a full size ski. Calculate the weight, then figure where the scale should be at. Which is a scale factor of 1.13611 .. plus a 5% safety factor (in case of variations in weight).. 1.193 - this brings the model to 11.558in long (1.6in longer than original) and 3.5in wide. Near perfect waterline, and still a ton smaller/lighter than other RC models. I think RTR it's around 350g.
 
Balduccimoto

Balduccimoto

Location
NYC/Long Island
Quinc said:
What about using the bottom half of a remote control jetski and printing off a top half that looks like a standup?
Click to expand...

Many reasons. None that I know of are jet drive. Many are very large. Other RC boats that include jet drive are very wide. Most of all, im at the point that it would be more work to graft a bottom deck from another hull. Not only that - I am very stubborn. That is a kool video though. I did some googling and that is an outdrive, dual brushless, and they aren't made anymore. They were $450 :eek: I like how it jumps out of the water though.
 
Balduccimoto

Balduccimoto

Location
NYC/Long Island
Playing around with sheet metal.. All stainless hardware. Oh and I modified the entire hull. Ignore the rough edges. They will get hammered out last. If you have ever tried to model something like this with a solids program .. You would understand. It would have been better to model with another program, but then there is the issue of converting to a solid model for 3D printing.

Hood%20Hook%20System_zpsqfhklwgy.jpg

Hood%20Hook%20System2_zpstilomt9y.jpg
 
You must log in or register to reply here.
Top Bottom