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Old 01-07-2012, 11:41 PM   #121
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I worked on the battery tray design in Solidworks today..that will allow me to mount the battery over the belt.. the secret is the battery. The post made by mos_leung gave me the idea of using the Yokomo 2800mah 7.4 battery. Which is about the same size as a 1s lipo.. so its only 18.5mm tall.



The only draw back to the battery is the low capacity.. fortunately, I will only be running this car in 17.5 blinky and 17.5 open. I'm pretty sure 2800mah will be enough for these classes.. if someone were to drive this in modified.. it most likely wouldn't have enough capacity.. yet, this car is designed for the future , and I believe that battery technology would eventually catch up and I'm sure a battery the same size as the Yokomo but a higher capacity will eventually come out. At this time... this car wouldn't be produced because the design of the car isn't ROAR approved. But in the future... possibly.

The battery weighs 146g compared to a shorty lipo at 213g. In order to raise the battery up over the belt and make up the weight.. I had to design a battery tray. It is 93.5mm x 46mm and is only 18.5mm tall. With pretty much all of the new shorty lipo's are 25mm tall.. this gives me 6.5mm for the battery tray.

Here are some CAD images of my battery tray design.. it is side loading.. to get the battery out all you have to do is unscrew the thumb screw with a threaded rod on in..and pulled it out, open the battery door and sliding the battery out. This makes it so I don't have to bottom load the battery like the E4 and the Jrx-s

The tray will be secured to the chassis by four screws..separating the chassis and the tray will be four o-rings.. I'm hoping that this will allow the chassis to flex. So the tray will actually be "floating" about 1mm above the chassis. Additionally, the third layer of the tray that connects the two sides..of the tray will be 1mm lexan.. this will also help the chassis to flex as it should.

On the bottom of the tray are slots for lead weights.. you can slide the weights forward and backward in order to get perfect 50/50 weight. Also, you can slide the battery forward and backward. A foam spacer fills the extra space.

The first layer on the tray will be made out of 3mm aluminum , the second layer will be made out of 2mm aluminum, the third layer out of 1mm lexan, the battery braces 3mm carbon, and the battery braces which go over the battery will be 6mm lexan.

The belt will run under the tray in the channel. The channel allows 6mm of clearance for the belt.






Here is a picture comparing the height of a shorty lipo compared to the Yokomo battery in my tray.. The top of the Yokomo battery in the tray will be at 25.5mm..only .5mm higher than a normal stick battery


Quote:
Originally Posted by valk View Post
i dont have a tc6 so this might be a dumb question, but why did you have to double up the diff pullies like that? couldn't you have just placed the difs both on the same side? belt would be slightly offcenter but is that really that big a deal? also curious how your gonna mount the battery low with the belt arranged like that. kinda defeats the purpose of moving your motor to center if the battery is still sitting outboard to clear the belt.
even with a stubby lipo would have to add a lot of weight on the other side to balance with the battery. electronics wont be even close.
average brushless motor = 170gr average 7.4v hard lipo 280gr.
I have a couple reasons for doubling up on the diff pully's in order to move the belt to the center. The first reason is that I can switch between running two belts and a single belt with two diff pulleys..allowing me to experiment and tune the drive-train depending on the traction level and power of the motor. Since I have two pully's in the rear I could run one belt from the drive pulley to diff pulley closest to the bulkhead..and then run another belt on the center diff pulley to the front center pulley. The second reason is that if the belt was offset then the channel in the battery tray shown above would also have to be offset..which would then cause the battery tray to be unbalanced. The battery will be placed in the exact center of the chassis.

Quote:
Originally Posted by Xpress View Post
I don't know if this will come into play or not, but I think one of the reasons the xxxs drivetrain worked was because the tensioner pulley was used on the "slack" side of the belt. Under load the drive pulley pulled the belt tight between it and the rr diff pulley and then the front diff pulley. All of the wrap around the tensioner was never high load.

With your current design the drive pulley is putting drive tension into the belt as it snakes its way around the tensioner.

Does this make any sense?

I like the way you have run the belt around the motor, but perhaps the layshaft would be better in front of the motor?

Hmm.. I do understand what your saying..and it does look like the belt would be putting force on the idler as the car accelerates.. I too am not sure if this would come in play.. we will just have to see. Unfortunately, the drive pulley has to be in back of the motor for the layout to have good front/rear distribution... so if I can't seem to a get the one-belt system to work.. I can just switch to a two-belt system.


Quote:
Originally Posted by daleburr View Post
Stubby Lipo = 200g

Servo = 50g
ESC = 80g (with wires)
Receiver = 10g
Transponder = 5g
TOTAL = 145g

So it's not that far off, especially as the car is likely to be light and require lead to get it upto any sort of minimum weight, so this can be put on the electronics side.
Since the battery is going to be dead in the middle of the chassis.. the weight will be divided like this..(the battery weight will cancel out left/right)

Right:
Esc: 55g (with wires)

Total = 55g

Left
Servo: 44.5g
Receiver: 3.1g

Total= 47.6g

Last edited by eds24; 01-08-2012 at 12:29 AM.
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Old 01-08-2012, 03:58 AM   #122
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Sorry bro , 2800 wont be enough , we pull 2100mah in 17.5 timed and notice a drop off using 5500 packs

people will be flying past u after 1 minute
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Old 01-08-2012, 09:18 AM   #123
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Quote:
Originally Posted by Yokojojo View Post
Sorry bro , 2800 wont be enough , we pull 2100mah in 17.5 timed and notice a drop off using 5500 packs

people will be flying past u after 1 minute
Agreed, the pack won't be flat by the end of the race, but the voltage will have dropped enough that it will lose a lot of performance. Under acceleration (when the voltage drops even more) it may also get low enough to trigger the voltage cutoff.

I'd test this pack in a normal car before designing anything around it, to confirm for yourself.

Most of the guys who race the slower motor classes run big capacity packs to keep the voltage as high as possible for the whole race. In comparison the mod guys often only run 5000s as they have plenty of power to spare and don't want the extra weight/size.
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Old 01-08-2012, 09:56 PM   #124
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I've been following this project since the beginning and really liked it for the out-of-the-box thinking. but now i'm a bit disappointed as the original plans were scrapped in place of conventional, centerline tranny/belt, design.
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Old 01-09-2012, 06:37 PM   #125
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Quote:
Originally Posted by ShrewdRacer View Post
I've been following this project since the beginning and really liked it for the out-of-the-box thinking. but now i'm a bit disappointed as the original plans were scrapped in place of conventional, centerline tranny/belt, design.
+1

i still think the way your belt is routed is gonna put a lot more drag on the driveline than the way you were doing it before. but, if it works, good on you. i would have stuck to the shaft and just cut slots for strapping tape in the chassis. all you would have needed to make would be bearing holders for the shaft.
but, you got what you got now. its very interesting. we will just have to see how the performance works.
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Old 01-10-2012, 04:20 AM   #126
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After Yokojojo and Daleburr pointed out that the 2800mah would have enough capacity but the voltage would drop too quickly on the voltage curve to stay competitive with the other cars.. I went back to the drawing board for the last couple of days trying to find solutions.



First I looked at making a custom battery by finding individual cells and soldering them together and making a custom case.. but I couldn't find cells that had the right combo of capacity, C rating, and correct dimensions. So I started looking at airplane r/c batteries and considered wiring a couple of those like saddle packs, I also looked at a couple very small saddle packs made by Maxamps.


After lots of searching a research I came to the conclusion that the best solution to this problem is to offset the belt, offset a short lipo, and fill the remaining space with the electronics. I was avoiding this because the battery is the heaviest component on the chassis.. but after a quick trip to the Post Office to weigh my Tc6 chassis with only a motor in it I found it weighed 1038g. I added up the weight of my esc,servo, and rx and found that the battery would have to weigh 336g in order for the car to meet the minimum weight. I realized that no matter wiether weight is steel ballasts or a lipo battery its all weight. Its going to end up being a similar layout as the 3-belt Tcx ..but with one or two belts..
So here is what I have come up with...




As you can see the belt will now be offset this allows for the battery to moved in towards the center. Additional weight will be added to the electronics side to help balance the car.. this additional weight will get the car close to minimum weight..leaving a few grams to balance the front-to-rear currently.

I'm still trying to figure out how to mount the battery.. I'm leaning towards tape.. though I hate it. The battery will be able to slide to the back or to the front for different weight distribution.

This layout will allow for lots of space for the electronics.. but also allow me to use a Promatch 4000mah 40c short lipo pack.

My belt should be coming Wednesday.

Quote:
Originally Posted by Yokojojo View Post
Sorry bro , 2800 wont be enough , we pull 2100mah in 17.5 timed and notice a drop off using 5500 packs

people will be flying past u after 1 minute

Quote:
Originally Posted by daleburr View Post
Agreed, the pack won't be flat by the end of the race, but the voltage will have dropped enough that it will lose a lot of performance. Under acceleration (when the voltage drops even more) it may also get low enough to trigger the voltage cutoff.

I'd test this pack in a normal car before designing anything around it, to confirm for yourself.

Most of the guys who race the slower motor classes run big capacity packs to keep the voltage as high as possible for the whole race. In comparison the mod guys often only run 5000s as they have plenty of power to spare and don't want the extra weight/size.
Thank you both of you for bringing this to my attention.. when I was doing my calculations.. I only made sure that the battery wouldn't run out of Mah's and didn't consider the voltage curve.

Quote:
Originally Posted by ShrewdRacer View Post
I've been following this project since the beginning and really liked it for the out-of-the-box thinking. but now i'm a bit disappointed as the original plans were scrapped in place of conventional, centerline tranny/belt, design.
I hope that you see that their is still quiet a bit of out-of-the-box thinking going on with this project.. I haven't seen a car that can switch between one-belt and two-belts before.. or a single-belt car with a centralized motor and a low layshaft like mine (except for wtcc's car).

From my past projects I have learned to keep things simple.. I feel like I am keeping my design simple yet.. implementing creativity and innovation in to my design to better the original design.. I'm sorry that you don't feel like its crazy enough for you.. but I can guarantee you won't see another car like this anywhere.

Quote:
Originally Posted by valk View Post
+1

i still think the way your belt is routed is gonna put a lot more drag on the driveline than the way you were doing it before. but, if it works, good on you. i would have stuck to the shaft and just cut slots for strapping tape in the chassis. all you would have needed to make would be bearing holders for the shaft.
but, you got what you got now. its very interesting. we will just have to see how the performance works.
If I find that the one-belt system isn't working out I can simply switch to a two-belt system which would be more efficient than two-belts and a shaft. And like I have said... to actually make that design a reality.. would have taken more work than it seems and it would've been less efficient, not as elegant, along with more complicated.
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Old 01-10-2012, 06:01 AM   #127
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I think you made a good decision on the battery side, because on most events only ROAR/EFRA legal batteries are allowed.

Unfortunately you have to give up your symetrical design which really looked attractive. I would like to see you saving it, but I know how hard it is to place the components, even if you have a custom chassis. But sometimes new doors open. Try to simulate more with SolidWorks. Before starting my KR1-project I build all parts and electronics, even screws in CAD (Rhinoceros) and pushed everything around in there. This really helps and gives you new ideas for problems.

Keep your head up. I am sure you will find a satisfying solution for yourself (and us )!
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Old 01-10-2012, 06:46 AM   #128
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Just another point I am not sure if you have considered when weighting things is the weight of a body?... I can usually count on a body + body pins etc adding another 100g to a car... I probably have them on the heavy side but it needs to be considered... so if you have 336g to play with its actually only 236g if you allow for a body
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Old 01-10-2012, 08:51 AM   #129
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Saddle packs design would be a lot easier.
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Old 01-10-2012, 11:02 AM   #130
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Quote:
Originally Posted by eds24 View Post
I hope that you see that their is still quiet a bit of out-of-the-box thinking going on with this project.. I haven't seen a car that can switch between one-belt and two-belts before.. or a single-belt car with a centralized motor and a low layshaft like mine (except for wtcc's car).

From my past projects I have learned to keep things simple.. I feel like I am keeping my design simple yet.. implementing creativity and innovation in to my design to better the original design.. I'm sorry that you don't feel like its crazy enough for you.. but I can guarantee you won't see another car like this anywhere.

don't get me wrong though.. any custom chassis is still a lot of time and money so kudos to you man. i just thought your original design were more interesting, and unique. and doesn't this design kinda defeats your original reason for creating a new chassis, which is to use a shorty lipo and put the heaviest components on the center for better weight distribution?
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Old 01-10-2012, 05:52 PM   #131
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Quote:
Originally Posted by ShrewdRacer View Post
don't get me wrong though.. any custom chassis is still a lot of time and money so kudos to you man. i just thought your original design were more interesting, and unique. and doesn't this design kinda defeats your original reason for creating a new chassis, which is to use a shorty lipo and put the heaviest components on the center for better weight distribution?
I also want to see your original design...motor, short LIPO in center with shaft...etc.
How about using TC3/4 gear box with slight off center main shaft ...like the 1/8 engine buggy to eliminate torque steering......
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Old 01-11-2012, 01:44 AM   #132
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I spent another day looking for a lipo battery that would allow me to keep the battery in the center of the chassis... the closest I found as a 3600mah 20c battery that I would have to make a custom case for. I still am not sure that would provide me enough power.

Its possible that I could put a 4000mah shorty lipo in the center of the car.. but I would have to cut a slot all the way down the chassis... and raise the battery up to a total height of 28mm. In order to fit the servo in I would have to stand up a low profile servo up and also put the esc on its side.

The lipo battery technology just isn't to the point where they can pack enough power into the size it would take to put a lipo in the center of the chassis without having to raise the COG of the car. Once a battery comes out that is small enough to do so and has enough capacity.. I certainly can change the layout of my car. But, till then I think the new layout that I posted above is the best. And it is still an improvement to the cookie-cutter touring car layout.


Quote:
Originally Posted by wtcc View Post
I think you made a good decision on the battery side, because on most events only ROAR/EFRA legal batteries are allowed.

Unfortunately you have to give up your symetrical design which really looked attractive. I would like to see you saving it, but I know how hard it is to place the components, even if you have a custom chassis. But sometimes new doors open. Try to simulate more with SolidWorks. Before starting my KR1-project I build all parts and electronics, even screws in CAD (Rhinoceros) and pushed everything around in there. This really helps and gives you new ideas for problems.

Keep your head up. I am sure you will find a satisfying solution for yourself (and us )!
Not only would that layout allow me to use a ROAR/EFRA approved battery.. but the layout is Roar legal.. a saddle battery can fit in the same spot.. it would just be hanging off the ledge. Ofcourse, I would be using a short lipo.. but it's legal because it can accept saddle packs haha

I much much rather keep the center battery..but, the battery technology isn't their yet.. once the lipo's get small enough with enough capacity I can change the layout. The only thing is its a bit hard to put everything into Solidworks without disassembling everything. But, I do know what you mean that putting everything it Solidworks first helps.. being able to move everything around. I was going to put the entire car into Solidworks ,but I'm going to have to do that after I finish it.


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Originally Posted by ShadowAu View Post
Just another point I am not sure if you have considered when weighting things is the weight of a body?... I can usually count on a body + body pins etc adding another 100g to a car... I probably have them on the heavy side but it needs to be considered... so if you have 336g to play with its actually only 236g if you allow for a body
Yep, I weighed it with the body and the pins. Crazy how much those things can add to the weight.

Quote:
Originally Posted by Jochim_18 View Post
Saddle packs design would be a lot easier.
Perhaps.. but, in order to put the belt inbetween the saddles I would have to create a channel 8mm wide.. this would push the batteries farther out on the chassis than how I have short battery positioned right now.

Quote:
Originally Posted by ShrewdRacer View Post
don't get me wrong though.. any custom chassis is still a lot of time and money so kudos to you man. i just thought your original design were more interesting, and unique. and doesn't this design kinda defeats your original reason for creating a new chassis, which is to use a shorty lipo and put the heaviest components on the center for better weight distribution?
I do agree with you that my initial design using 2 belts and a shaft was more interesting. It's just that after looking at that design for a long time.. it looked like a lot could wrong because it was complicated and lots of parts and I wasn't sure I could make parts precise enough with my hand tools and drill press to make the shaft work.

I much rather prefer to have a centralized motor and battery but, in the end the reason for moving these components to the center of the chassis was to make the car faster/handle better than the original TC6.. and as long as I meet that goal then it is worth it to make a custom car. This car will still be an improvement over the TC6 because the motor will be moved to the center of the car (30mm) and the battery is being moved towards the center of the car about 10mm. Also, the car can use a single belt or dual belts.

Quote:
Originally Posted by mos-leung View Post
I also want to see your original design...motor, short LIPO in center with shaft...etc.
How about using TC3/4 gear box with slight off center main shaft ...like the 1/8 engine buggy to eliminate torque steering......
Unfortunately, I can't use Tc3/4 gear box's with the Tc6's bulkheads. Also, since the motor is in the middle of the chassis right now their would be no way to route the shaft unless I turned the motor 180 degrees. Also, the offset shafts on the 1/8th buggies was made to move the engine closer to the center of the chassis not to eliminate torque steer.
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Old 01-13-2012, 07:32 AM   #133
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Perhaps.. but, in order to put the belt inbetween the saddles I would have to create a channel 8mm wide.. this would push the batteries farther out on the chassis

You won't feel the difference with saddle packs mounted side by side. The little space will be so minor. And in my opinion better in 2 ways over your current design. (1) the batteries sit as low as possible and (2) saddle packs have as much capacity as the standard packs. Your chassis will be completely balance. For your info. A certain factory racer that's made A-Mains at 1/10th scale worlds told me at last years reedy. I think the ticket with brushless and lipo will have the motor centralized and sddle pack batteries.
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Old 01-25-2012, 07:58 PM   #134
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Any updates on your design eds??
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Old 01-27-2012, 10:08 PM   #135
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