17LikesGT8 Class--buggy-based on road electric!
02-27-2013, 12:39 PM
#3241
Here is some information I posted in another thread:
If we now look at two cars same type, same weight, one running with 4s the other one with 6s racing side by side doing same lap time.
In that case the amout of mechanical energy used to do so will be exactly the same. Considerd that the efficacy of both motor/esc combos is the same this should also be true for the amout of electrical energy delivered by the battery.
But even if so, the car runnig 6s will have only 66% of the current. To give an example for a theoretical peak power of 2000 watts 4s will show 135 Ampīs, 6s only 90 Ampīs.
135 Ampīs is clearly above what banana plugs can handle, means that hardcase lipos equipped with those are on the risky side. They are rated for less than 100.
Donīt know what the spec for the deans is.
Also the esc will have to handle the higher current may be decreasing reliability.
Looking at the two motors matched at same peak rpm at full voltage the one for 4s will have lower KV rating and more winds than the the one for 6s. So normaly more winds will show more resistance.
The powerlosses (beside other effects) in the esc and the motor are generated by their internal resistance. Powerloss can be calculated by P=I*I*R, means it does grow with the square current.
So even if both the esc and the motor do show same resistance 6s will be up front.
If there are no other major effects turning that upside down this would be a good baseline to start with.
As soon as we get rid of snow and rain here it is time to proof the theory by pratical testing.
Donīt think that 4s or 6s does make a big difference in performance if you set the duration of the heats long enough.
The total amount of energy stored in both possibilities is almost the same if the total weight of the batteries is the same.
Of course you can have more total energy with 6s, but only if you are willing to accept the extra weight as a penalty.
The 2s hardcase with the highest capacity available from Team Orion will give you 8000mAh.
Total energy stored with two packs will be 118.4 Watt. Weight is 628 g.
The equivalent in 3s might be a gens ace 5300mAh with 117.66 Watt stored using two of them, but the total weight will be 876 g.
The difference in weight is 248 g and will, over a complete heat, equalize the advantage of the 6s but making more peak power available.
You most probably not able to use too often if you want to race until the end of the heat.
The advantage you will keep is running lower currents and lower temperatures giving better reliability at least from a theoretical point of view.
Agreed that is a theoretical analysis based on what is available as a usefull maximum with 4s and 6s.
The total amount of energy stored in both possibilities is almost the same if the total weight of the batteries is the same.
Of course you can have more total energy with 6s, but only if you are willing to accept the extra weight as a penalty.
The 2s hardcase with the highest capacity available from Team Orion will give you 8000mAh.
Total energy stored with two packs will be 118.4 Watt. Weight is 628 g.
The equivalent in 3s might be a gens ace 5300mAh with 117.66 Watt stored using two of them, but the total weight will be 876 g.
The difference in weight is 248 g and will, over a complete heat, equalize the advantage of the 6s but making more peak power available.
You most probably not able to use too often if you want to race until the end of the heat.
The advantage you will keep is running lower currents and lower temperatures giving better reliability at least from a theoretical point of view.
Agreed that is a theoretical analysis based on what is available as a usefull maximum with 4s and 6s.
In that case the amout of mechanical energy used to do so will be exactly the same. Considerd that the efficacy of both motor/esc combos is the same this should also be true for the amout of electrical energy delivered by the battery.
But even if so, the car runnig 6s will have only 66% of the current. To give an example for a theoretical peak power of 2000 watts 4s will show 135 Ampīs, 6s only 90 Ampīs.
135 Ampīs is clearly above what banana plugs can handle, means that hardcase lipos equipped with those are on the risky side. They are rated for less than 100.
Donīt know what the spec for the deans is.
Also the esc will have to handle the higher current may be decreasing reliability.
Looking at the two motors matched at same peak rpm at full voltage the one for 4s will have lower KV rating and more winds than the the one for 6s. So normaly more winds will show more resistance.
The powerlosses (beside other effects) in the esc and the motor are generated by their internal resistance. Powerloss can be calculated by P=I*I*R, means it does grow with the square current.
So even if both the esc and the motor do show same resistance 6s will be up front.
If there are no other major effects turning that upside down this would be a good baseline to start with.
As soon as we get rid of snow and rain here it is time to proof the theory by pratical testing.
03-03-2013, 11:27 AM
#3242
Tech Adept
Kyosho Inferno GT with Lancia Integrale body
Last edited by dark_luna; 03-03-2013 at 12:00 PM.
03-03-2013, 12:23 PM
#3244
Tech Adept
03-03-2013, 08:01 PM
#3245
Tech Adept
03-04-2013, 04:42 AM
#3246
Tech Addict
Hello from France,
here's my Citroën DS3WRC !!!
here's my Citroën DS3WRC !!!
03-13-2013, 06:57 PM
#3248
Ready to take the plunge into GT8
So I have been doing a TON of reading on these class of cars, and I have to say that I am ready to take the plunge and build a "personal" custom modified platform. I am still working out the details and materials though. I know what power system I am going to use, and I have a vehicle that I am going to convert/modify.
The platform I am going to use is a double edge sword...awesomely strong parts for wear and strength, but no parts to convert to on road as the manufacturer only offers buggy and truggy flavours at this time. I do like to tinker and make my own parts, so I am welcoming the challenge.
I am looking for some insight on an issue from those with experience with this class:
What wheel base to use? I see some cars are on the 320-330mm wheelbase and then there are the longer wheel base platforms (360 mm). How are the longer chassis cars for performance compared to the shorter wheel base cars?
I know from reading that longer chassis provides more straight line stability under acceleration, but how are they in tight technical turns compared to the shorter chassis cars?
I would like to have lots of body styles to choose from. I realize there are more bodies currently available for the shorter wheel base, but the longer wheelbase bodies look better and more realistic in my opinion...for GT that is, not many rally style for it.
The vehicle I want to build/design will be designed for on road GT and also easily converted for flat dirt track rally style (off road track, but no big jumps, just varying terrain and small humps for minimal air). I my even dabble with drifting as I do have a couple extra diffs that I can lock up!
So, not to turn this into a chassis debate, but more of a size debate, is bigger truly better?
More questions to come....
Thanks!
The platform I am going to use is a double edge sword...awesomely strong parts for wear and strength, but no parts to convert to on road as the manufacturer only offers buggy and truggy flavours at this time. I do like to tinker and make my own parts, so I am welcoming the challenge.
I am looking for some insight on an issue from those with experience with this class:
What wheel base to use? I see some cars are on the 320-330mm wheelbase and then there are the longer wheel base platforms (360 mm). How are the longer chassis cars for performance compared to the shorter wheel base cars?
I know from reading that longer chassis provides more straight line stability under acceleration, but how are they in tight technical turns compared to the shorter chassis cars?
I would like to have lots of body styles to choose from. I realize there are more bodies currently available for the shorter wheel base, but the longer wheelbase bodies look better and more realistic in my opinion...for GT that is, not many rally style for it.
The vehicle I want to build/design will be designed for on road GT and also easily converted for flat dirt track rally style (off road track, but no big jumps, just varying terrain and small humps for minimal air). I my even dabble with drifting as I do have a couple extra diffs that I can lock up!
So, not to turn this into a chassis debate, but more of a size debate, is bigger truly better?
More questions to come....
Thanks!
03-17-2013, 09:00 AM
#3249
Wow, I guess I personally killed this thread!
03-17-2013, 09:58 AM
#3250
Guess thats too much honor for a basket of questions asked.
Beside the nicer loocking bodies there is one more argument for the long wheelbase when you go brushless. There is more room/length available to mout the batteries close to the centerline.
Also there are only reports from the nitro fraction tending to prefere the shorter wheelbase.
The difference between both is only the chassislength and one shorter/longer driveshaft. Anything else is the same.
What about some answers before you come up with new questions. You said you have already decided the platform. Let us know what it is.
Beside the nicer loocking bodies there is one more argument for the long wheelbase when you go brushless. There is more room/length available to mout the batteries close to the centerline.
Also there are only reports from the nitro fraction tending to prefere the shorter wheelbase.
The difference between both is only the chassislength and one shorter/longer driveshaft. Anything else is the same.
What about some answers before you come up with new questions. You said you have already decided the platform. Let us know what it is.
03-17-2013, 11:19 AM
#3251
I didn't think I asked a basket of questions. I was just wanting some opinions on longer wheelbase vs shorter wheelbase before I start doing some mods.
As for the platform I plan to use, it will be a brushless Z-Car ZMXB-8 Pro version.
Just to let you know (not trying to be snotty, I realize tone is lacking on forums), I am not a noob when it comes to building and modifying rc cars. I have already done a brushless conversion on my buggy with some custom, one-off parts and COTs parts. It didn't look pretty, but it was very functional and durable!
I am not too concerned about fitment for batteries, they will fit nicely (planning for 4S single pack, no plans for dual 2S). I am wondering more on the performance aspect, namely turning ability when on and off power and straight line stability when on and off power.
Seeing that I would like to be able to utilize this vehicle in several different ways (with a few setup changes, eg. off-road rally and on-road drifting) leaves me to ponder/figure out which chassis length would be optimal for what I am trying to achieve.
Currently as my car sits stock, the wheel base is about 324 mm. I could spread that out a little bit without changing the center driveshafts (2 mm tops). I do plan on putting in a spool to replace the center diff. The ofna dm1 spool will be a close drop in fit. I plan on ordering the spool shaft, then getting the spur from rc-monster. This hop up may allow me a few more mm in chassis length when I make a new chassis.
I am planning on experimenting with making a carbon fiber (CF) chassis (when the weather gets warmer). The raw supplies for CF are getting cheaper compared to a few years ago. I have access to a wood working shop to aid in making molds and such. I am rather handy when working with wood. I do realize that CF is not wood, and there are health concerns when working with carbon fiber. From all the research I have done on CF, it doesn't look impossible to do. Even though I don't have access to a CNC machine, I do have other tools that can be used to form/mill the chassis.
I enjoy the challenge of making my own parts and customizing my vehicles. (makes it easier to find if it gets stolen
)
Thanks for the reply. I was starting to think I killed the thread!
As for the platform I plan to use, it will be a brushless Z-Car ZMXB-8 Pro version.
Just to let you know (not trying to be snotty, I realize tone is lacking on forums), I am not a noob when it comes to building and modifying rc cars. I have already done a brushless conversion on my buggy with some custom, one-off parts and COTs parts. It didn't look pretty, but it was very functional and durable!
I am not too concerned about fitment for batteries, they will fit nicely (planning for 4S single pack, no plans for dual 2S). I am wondering more on the performance aspect, namely turning ability when on and off power and straight line stability when on and off power.
Seeing that I would like to be able to utilize this vehicle in several different ways (with a few setup changes, eg. off-road rally and on-road drifting) leaves me to ponder/figure out which chassis length would be optimal for what I am trying to achieve.
Currently as my car sits stock, the wheel base is about 324 mm. I could spread that out a little bit without changing the center driveshafts (2 mm tops). I do plan on putting in a spool to replace the center diff. The ofna dm1 spool will be a close drop in fit. I plan on ordering the spool shaft, then getting the spur from rc-monster. This hop up may allow me a few more mm in chassis length when I make a new chassis.
I am planning on experimenting with making a carbon fiber (CF) chassis (when the weather gets warmer). The raw supplies for CF are getting cheaper compared to a few years ago. I have access to a wood working shop to aid in making molds and such. I am rather handy when working with wood. I do realize that CF is not wood, and there are health concerns when working with carbon fiber. From all the research I have done on CF, it doesn't look impossible to do. Even though I don't have access to a CNC machine, I do have other tools that can be used to form/mill the chassis.
I enjoy the challenge of making my own parts and customizing my vehicles. (makes it easier to find if it gets stolen
) Thanks for the reply. I was starting to think I killed the thread!
Last edited by Galeleo; 03-17-2013 at 11:40 AM.
03-17-2013, 12:39 PM
#3252
Did I misread that as some kind of humor ? Sorry if so.
Here is a link about the same car with a lot of pictures:
http://www.rc-monster.com/forum/showthread.php?t=12295
Is it still available ?
It has some very interesting features making it a good candidate for an onroad conversion. Does it have a front kick up ? Canīt see that on the pictures.
The major differenc between offroad and onroad cars is suspension geometry and ride height. Looks like a lot can be adjusted without the need of making too many new parts.
Some target values to start would be:
Front caster: 7-10°, rear tow in: 3° +/- 1°, camber: 2° +/- 1°, ride height: 8 mm +/- 1 mm, sway bars 2.8 - 3 mm (front/rear) and stiffer springs all around. Diff oil you need to figure out your own strategy if you still like to do some light offroad.
Those just in case you have not already found them.
I would not worry about changing the wheelbase by a few mm, thatīs not worth the effort.
Here is a link about the same car with a lot of pictures:
http://www.rc-monster.com/forum/showthread.php?t=12295
Is it still available ?
It has some very interesting features making it a good candidate for an onroad conversion. Does it have a front kick up ? Canīt see that on the pictures.
The major differenc between offroad and onroad cars is suspension geometry and ride height. Looks like a lot can be adjusted without the need of making too many new parts.
Some target values to start would be:
Front caster: 7-10°, rear tow in: 3° +/- 1°, camber: 2° +/- 1°, ride height: 8 mm +/- 1 mm, sway bars 2.8 - 3 mm (front/rear) and stiffer springs all around. Diff oil you need to figure out your own strategy if you still like to do some light offroad.
Those just in case you have not already found them.
I would not worry about changing the wheelbase by a few mm, thatīs not worth the effort.
03-17-2013, 12:54 PM
#3253
Thanks for the link, it has been awhile since I read that one. I used that thread years ago when I first did my brushless conversion. Total trip down memory lane.
I have had the car for almost 4 years now, and it is still available! Just bought some parts recently to freshen it up too.
The reason that I am asking about the chassis length, is that I plan to make a CF chassis, and if it is better to go with a longer chassis, then I can design for that. I am still on the fence as to the final size though.
I did to a rough mock up with similar values as to what you have posted. The ride height does seem to put the suspension arms and drive shafts at an odd angle though.
My chassis does have front and rear kick up. Not sure the exact angle. When I attempt to make a CF chassis, I will not be putting in the kickup, the chassis will remain totally flat.
I have had the car for almost 4 years now, and it is still available! Just bought some parts recently to freshen it up too.
The reason that I am asking about the chassis length, is that I plan to make a CF chassis, and if it is better to go with a longer chassis, then I can design for that. I am still on the fence as to the final size though.
I did to a rough mock up with similar values as to what you have posted. The ride height does seem to put the suspension arms and drive shafts at an odd angle though.
My chassis does have front and rear kick up. Not sure the exact angle. When I attempt to make a CF chassis, I will not be putting in the kickup, the chassis will remain totally flat.
03-17-2013, 01:26 PM
#3254
Most of the bodies on the market are made for short wheelbase, unfortunately many of them do look toy`ish. They are all made for 325 mm wheelbase.
Most of the long wheelbase bodies do come from Kyosho and are 360 mm wheelbase.
Some of them such as Audi R8 and the Corvette are very nice, but also very expensive.
There is for shure a lot more handling and drivebility hidden in the overall setup than just defined by the wheelbase.
Go for the body you like and adjust the reminding parts accordingly. If you going to make a carbon chassis anyway it is only one longer driveshaft you need.
Most of the long wheelbase bodies do come from Kyosho and are 360 mm wheelbase.
Some of them such as Audi R8 and the Corvette are very nice, but also very expensive.
There is for shure a lot more handling and drivebility hidden in the overall setup than just defined by the wheelbase.
Go for the body you like and adjust the reminding parts accordingly. If you going to make a carbon chassis anyway it is only one longer driveshaft you need.
03-17-2013, 04:37 PM
#3255
new gt8 body
Hello all you GT racers, I just wanted to let you know that there will soon be a new GT body. I am still working out a few design changes but I thought I would give you guys a little peak at what's to come.
Thanks, for looking.
Introducing the new PROMAR GT1
Thanks, for looking.
Introducing the new PROMAR GT1