Custom Carbon Fiber Brushless RC8T Pics

[Ryu James]

offended?! why? dont sweat it! i wish you were right and i did have the motor but i dont. no worries, man.

[Ryu James]

so get this everyone. despite how much i loved my carbon fiber chassis i knew that it had to do with why my RC8T wasnt jumping right. so i took some 1/8" alum 7075 plate and made another chassis with the exact same layout. this time i put the kickup in the front. i didnt change any settings whatsoever on the truck at all. as expected the truck jumps amaxing now. no more nose dives. it handles the same as the CF chassis but jumps much better. also, the truck is a lot louder now with the alum chassis. i have some theories about the resulting changes though.

so first, i dont think that it jumps better now because of the kickup. i think it jumps better due to chassis flex. when i had the 5mm cf chassis off i tried to bend it. the thing will not even bend 1mm when trying to break it over my knee. the 3mm 7075 alum however i can bend with my hands at least 5-7mm of flex. i think this is what makes all the difference. because there is no flex in the cf chassis the rear wheels are launched harder up when coming off the jump. the flex of the alum tends to absorb some of this force resulting in a more balanced flight. i think if i had gone with a 3mm cf it would have some flex to it and work out better. may try that down the road.

secondly, why is the alum more noisy? i had never thought about it before but obviously the entire chassis of the truck vibrates when running. hence why we use threadlock. this vibration is audible. the 5mm cf has a much greater sound dampening quality over any kind of metal. you guys should have heard it. it was the coolest sounding truggy you have ever heard. it was like a silent 60mph stealth. the alum chassis now just sounds like any other truggy i have driven. kinda disappointing but it is more important that it jumps right. anyway, the alum chassis is not realy pretty. just a temporary until Mikes RC8T conversion kit gets here. i bought it a few days. so i will use that chassis when it arrives. cant wait.

sucks that i spent all that time and money on that 5mm cf chassis only for it to not work as well as i had hoped. i thought about getting 3 or 4mm but i didnt want to take any chances of the chassis breaking on a huge jump. seeing the quality of the cf from dagraphite now i know that it would not break. in fact, i am more concerned that even if i went with 3mm there would still not be enough flex for it to perform right. they make some super strong carbon.

i should have the new RCM RC8T kit tomorrow and i will be sure to post the build when finished.

[Raney120]

Ryu looks good I agree on the chassis flex I used to have the aluminum chassis braces on my 8ight T but took them off because I felt it didn't jump as well. When I drove a friends RTR 8ight T it felt even better than mine since the RTR chassis flex's alot more. I want to try a Flex chassis but haven't been able to get myself to drop the coin on it yet.

[Ryu James]

Raney,
you finish that 8t yet? throw a new thread up. i want to see that MMM 2200kv monster in there! how does it drive? tell me you finished it!

[Raney120]

Yeah I got a thread in the Castle Section here's a link http://www.rc-monster.com/forum/showthread.php?t=17438

[florianz]

sorry to hear that you're not happy with the "kick-up-free" chassis. that chassis rocks, great looks.
I started to build myself a carbonfiber-chassis some months ago, but got stuck due to the kick-up problem. First I wanted to do build it without kickup, but I ve been told that there's a kickup for a reason.

I have already cut two pieces of carbonfiber (aproxx 1,7mm thick each, much cheaper like that) in the shape of the chassis, to glue it together as one piece. I had planned to have the front piece of the chassis made by a seperate piece of carbon, to realise the kickup. the seperated frontpiece where the front diff is mounted on, is "connected" to the chassis by two layers of aluminium (one top, one bottom, inbetween the cabon). the aluminium layer in the front is realising that kickup.
glued together with some good 2-component epoxy glue (there are big differences in quality), baked in the oven with around 70*c, it gets very strong. like that I would have a carbonfiber chassis, including a kickup. as you have such a brilliant piece of carbon, you could problably "add" a kickup afterwards.

the reason why I didn't finish it was that I would only have saved a few grams like that, approx. 100 grams or less, compared to the original one.

As I already have a "top-deck" made by a piece of Carbonfiber (approx.4x30cm), which connects the front, middle and rear diff, it's already quite stable. some folks say, a 1/8 buggy should not be too stiff, as a slightly flexible chassis is good for handling (I think mugen used to have a mbx chassis which was quite flexible, mbx4?).

the reason why i took the top-deck solution is because of the crappy plastic of the diff-boxes, wich is too flexible and like that killing the diff-teeth. like that it got a bit better, I now have some other diffs.

The other, more simple way would be to laminate the chassis, made by glass and carbonfiber. you take the original aluminium-chassis as a sample, and with some sayers of carbon and kevlar-cloths you build a new piece of carbonfiber.
This was my first idea, but the problem here is - working with carbonfiber-cloths for the first time - it might get not stable enough and too heavy. It takes some experience.

there was this guy in germany who made a selfmade lighweight-chassi (like a "u"-shape) for his losi-buggy, custom-made carbonfiber for 2s-lipos. supa-stable, supa-rigid, supa-lightweigh.

eg. this chassis is also made by more than one piece:
http://www.offroad-cult.org/Board/ma...ing-t8003.html

he's a real expert and solved it like that:
http://www.ace-cars.de/DE%20AC/Bilde...0Bild%201.html

About a week ago I emailed matrix about there chassis and asked if they are going to make a BL designed CF chassis for the 8 and he said its already in the works and has a proto-type being tested....but no idea how long till production. I had pics of the proto but erased b/c I lost interest in paying $200 for a chassis for my basher. Just not cost effective IMO.

[pb4ugo]

There are two relatively easy ways to get kick up on a CF chassis.

The first is to join flat CF to the stock Alum. nose at the steering posts. Mill each to half thickness (assuming they're the same thickness) and overlap right at the steering posts. The screws holding the steering posts in place will also clamp the chassis halves together. If you really want some extra reassurance, some Scotch Weld 2216 epoxy can be used on the joint.

The second is to mold it in yourself. Make a wood form with the required 7deg kick up. Finish with some poly. Lots of mold release wax. Lay up the CF in a traditional wet layup (tutorials all over the internet), some cotton batting around the edges, and stick the whole thing in a double sealed FoodSaver bag, draw the vacuum, and double seal the other end. Make the part oversized so you can cut off the rough edges. If you really want to be trick (and expensive), there is some pretty low temp pre-preg (180 deg cure) available. The foodsaver bag has a max temp of about 200 deg. Make the form out of Alum, polish well, and repeat the above except laying with the pre-preg cloth and setting in a 180 deg oven for 4 hours. Almost as good as commercially auto-claved CF, but with the kick. Only problem is the pre-preg needs to be ordered in larger quantities and can't last long enough to do onesies twosies.

[Ryu James]

@ florianz and pb4ugo:

:quote:The first is to join flat CF to the stock Alum. nose at the steering posts. Mill each to half thickness (assuming they're the same thickness) and overlap right at the steering posts. The screws holding the steering posts in place will also clamp the chassis halves together. If you really want some extra reassurance, some Scotch Weld 2216 epoxy can be used on the joint.
:quote:

this is exactly what i plan to do. i was going to do this from the beginning but thought i would try it without the kickup first cuz i would rather have one solid piece than a multi-piece unit. i have seen Matrix Concepts chassis' and have heard they hold up very well so i am sure it will work out. plus, where my CF is 5mm i am going to shave off 3mm and then place the kick up portion of the stock alum. chassis on bottom. this way the bottom will be flush and seamless. i will cut it in a puzzle type mesh up so it holds together well.

i will still have the issue of chassis flex though. so what i plan to do for this is mill out 2.5mm throughout several areas of the chassis. this wasnt an option before but through RCM i have met someone who is willing to mill any CF for me. (thanks Tim!!) i will pay of course but at least now this is an option. so i think we might be able to come up with a sweet CF chassis. maybe even somthing that could be worth producing. we'll see.

here is kinda what i am thinking. cutting the stock chassis along the line and then milling out the bottom 3mm of the CF chassis in the same shape. then using the steering posts as 2 of the 4 countersunk screws that will hold the two pieces together. i think it will work.

[pb4ugo]

Must be the same Tim that helped me with a .dxf file! Good guy.

[brushlessboy16]

Looks a whole lot easier with the aluminum front end... makes me want to have a go.


is there any other way to bond the aluminum to the carbon fiber

[pb4ugo]

Originally Posted by brushlessboy16

Looks a whole lot easier with the aluminum front end... makes me want to have a go.


is there any other way to bond the aluminum to the carbon fiber

See this:

Originally Posted by pb4ugo

There are two relatively easy ways to get kick up on a CF chassis.

The first is to join flat CF to the stock Alum. nose at the steering posts. Mill each to half thickness (assuming they're the same thickness) and overlap right at the steering posts. The screws holding the steering posts in place will also clamp the chassis halves together. If you really want some extra reassurance, some Scotch Weld 2216 epoxy can be used on the joint.

The second is to mold it in yourself. Make a wood form with the required 7deg kick up. Finish with some poly. Lots of mold release wax. Lay up the CF in a traditional wet layup (tutorials all over the internet), some cotton batting around the edges, and stick the whole thing in a double sealed FoodSaver bag, draw the vacuum, and double seal the other end. Make the part oversized so you can cut off the rough edges. If you really want to be trick (and expensive), there is some pretty low temp pre-preg (180 deg cure) available. The foodsaver bag has a max temp of about 200 deg. Make the form out of Alum, polish well, and repeat the above except laying with the pre-preg cloth and setting in a 180 deg oven for 4 hours. Almost as good as commercially auto-claved CF, but with the kick. Only problem is the pre-preg needs to be ordered in larger quantities and can't last long enough to do onesies twosies.

[brushlessboy16]

I read it....



Doesnt answer my question- i dont have a mill to take down the aluminum and carbon fiber..

[Ryu James]

Originally Posted by brushlessboy16

I read it....



Doesnt answer my question- i dont have a mill to take down the aluminum and carbon fiber..

BL_RV0 just did a post and mentioned he has a new manual milling tool and willing to do jobs for $15/hr.

[pb4ugo]

The Scotch Weld is the bonding agent to use. You can use plates above and below the junction for reinforcement, bonding them as well. Good epoxies such as this create a glue joint that is stronger than the material.