1/4 Scale Cracker Vid

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Lou the big white beast looks good.

At 180 seconds (as you probably know) your drawing close to 50 amps. I think that's to much for the 24v dewalt motor, but I may be wrong. When you add more cells the current will probably go up even more?
 
Hi Steve, I figure I'm between 35 and 45 amps. The cells hadn't been cycled since October, so I figure I pulled between 1800 and 2000mah out of them max. Everything was only warm. 32 cells should warm things up a bit :D
 
Hello Guys,

When you add more cells the current will probably go up even more?
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Higher cell count = lower current draw. :D On the flip side you need a motor that can handle the higher voltage or it's bye-bye brushes.

Steven got the goodies,thank you. BTW: one of the mini t boxes was banged up but the contents seem fine.

Paul.
 
Higher cell count = lower current draw.
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Higher cell count with the same setup doesn't equal more current draw Paul? I was always told to prop down when increasing cells in a setup.

Paul Sorry about the damage, we can make a claim with ups. I didn't box the order, but heard how he fitted the outboard in the box and was worried about that more than the mini t's!
 
Hey Lou

Did you spring for the aftermarket endbell/brushes for that motor? You know they (the robot people) say that the stock motor endbell/brushes won't live beyond 30v.
 
Did you spring for the aftermarket endbell/brushes for that motor? You know they (the robot people) say that the stock motor endbell/brushes won't live beyond 30v
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Not yet, I want to try and melt the stock one first. :D The Robot guys don't have free water cooling. I figure thats gotta bump her up a bit. The Mass of this motor is its biggest asset. You would have to be pulling major amps for a good length of time to heat the magnets through. The water cooling on the brushes is very easy to do and you have about a 1/2 inch of heat transfer area. My next test run will probley be done with 30 cells and I'll have a gps on to check speeds
 
Lou

for the same load, additional voltage leads to a proportional increase inc urrent draw

However as the load will be increased as the prop is trying to throw more water and at a higher rate may be closer to the the cube of the ratio of increase ie 1.33 cubed.

using the pitch of the 646 you are currently propped for 38 mph even with a lot of hull/prop - a 440 will give you about the same speed potential on 32 cells (remember a 40 mm diam prop submerged is like a 56 mm diam prop in surface drive)

I would try the 440 on 24 cells it is much closer to a realistic speed on 24 ie 28 mph (remember a 700BB maus bullet only runs about 23 mph on a submerged drive)

Also the submerged props for eco racing have a much longer thinner balde with a different profile across the blade. Not a wedge like a surfacing prop but more like a wing profile in the blade)

When you get it running with a little air - it should be a flier - absolutely excellent to see this one up and running

I am impressed with the work yoursefl and Ken are doing. Cant wait till post Christmas as I am going to go for it with the same sorts of setups in a 1/8th - yahoo! have to egt someone to video it - maybe by the end of January I will have something - also renovating house so i will be busy!!!!
 
Hi Andrew, The 646 I'm using is cut for subsurface

DSCN2595_small.JPG


So if I was pulling 40 amps on 24 cells, what would I be pulling with 30 cells, same setup?

Did you see this link on RR about the Data Recorders

http://www.eagletreesystems.com/CarDataRec...ProductInfo.htm

I think this would really help to fine tune these big setups and figure out some real numbers from these motors.

LOU
 
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LOU said:
Hi Andrew, The 646 I'm using is cut for subsurface
DSCN2595_small.JPG


So if I was pulling 40 amps on 24 cells, what would I be pulling with 30 cells, same setup?

Did you see this link on RR about the Data Recorders

http://www.eagletreesystems.com/CarDataRec...ProductInfo.htm

I think this would really help to fine tune these big setups and figure out some real numbers from these motors.

LOU
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WOW, nice stuff, thanks for posting the link here.

Steve
 
Lou

- a minimum of 50 amps but more likely around 80 amps

hence the recommendation of the smaller prop

as coutner intuitive as this may seem it will work

the peak efficiency on these motors is in the mid 30 amps at these voltages

a smaller prop is the place to start

btw - increase cells 2 at a time from 24 - take it easy you are th efirst with these motors and it woudl be great to see you work toward a successful outcome with them.
 
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I agree with Andrew

That motor, direct drive in that hull, with that prop, on 30 cells = CHERNOBYL :eek:
 
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Thanks Andrew and Doug. My next test will be around the 29th of December. If Dundas gets wiped off the map you know I was out testing :D

I will do a 24 cell run with a GPS before I start to bump up cell count.

Thanks
 
Just topped up the cells I used for the test run this morning. They took 1500 mah. Anybody wanna wager this setup won't smoke on 30 cells :D

LOU
 
OK, I have a 438, 440, 442 and a 445 I can work. They just seem so small :(

LOU
 
Lou when will you test again? If your numbers are correct it may not smoke. I figure your at 30 amps with 24cells and maybe 40-45amps with 32cells. But I'm not a wagering man(at least not on this setup :D ).
 
Hey Steve, Looks like the next test will be Dec 29th, weather pending. Not sure how many cells just yet. I may do another 24 cell run first and try and get the CG a bit back. So little testing time makes it hard to stick to baby steps and stick to the one change at a time rule. :(

LOU
 

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