3d printing fun. trying Postimage now

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tamiyadan
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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Mon Jan 08, 2018 2:21 am

got further along. Battery now has a small holder just for position now.
servo got a proper mount.
Lots more error correction.
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Re: 3d printing fun. trying Postimage now

Post by XLR8 » Mon Jan 08, 2018 6:10 pm

Hey Dan, you were probably already planning to do so but I'll go ahead and waste a post by requesting a quick video once you have it sorted out. Curious to see this thing in action. thanks.
Doug

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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Mon Jan 08, 2018 6:51 pm

eventually i plan to make a video, when i get it working better. I'm outputting the new chassis now and all the revised parts to try out on it.

the steering has the most changes.

the driveline seems to work fine at least from the limited area i tried it in.

it is way under geared and i knew about it from the start but i needed to start somewhere.

i can't do anything outside since there snow all over.

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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Tue Jan 09, 2018 4:20 am

new chassis re-design
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well i don't know how much you will gauge from this video.


using a rm-01 as a comparable.
The final gear ratio is close to box stock RM-01 4.5 verse FWD 4.3

the Rm-01 has a slightly smaller turning radius at low speed. you can also flick the rear end out like a typical RWD making the radius almost zero if doing doughnuts.

FWDs always understeer anyway. you have to brake hard before a curve and turn early. then kind of keep some power on through the entire curve.

the rear tires are still not here so right now the FWD chassis is racked backwards no idea how much effect it is having on final handling.

now the RM-01 is lighter both chassis with same radio equipment minus the battery
rm-01 534 grams.
FWD 619 grams. i can shave weight off the question is from where right now. plus i never balanced the chassis. nor took downforce measurements. i plan on a 3d printed body which will be heavier compared to the lexan bodies on the Rm-01
my 3d print F1 857 grams (no battery)

keep in mind the RM-01 is using a 380 sized motor while the FWD is 540, there is a weight and power difference.
both cars are using 6V batteries. i will play around with LiFE verse NICD weights.

the foam tires for either car are sliding around on my wood floors, have not had a driveway test yet.

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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Wed Jan 10, 2018 3:03 am

Awesome i found the missing steering in my design. new mock up is giving me additional ideas for changes.
the low speed control is good now.

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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Fri Jan 12, 2018 4:40 pm

more changes
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Re: 3d printing fun. trying Postimage now

Post by XLR8 » Fri Jan 12, 2018 8:21 pm

Thanks Dan. The video is pretty good however I'm really looking forward to when you can get the car onto a surface with good traction. I reckon it's a whole different driving experience.
What are the new changes?
Doug

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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Sat Jan 13, 2018 4:30 am

the correct rear tires just showed up today so i have that sorted.

changes. well there are so many, some due to clearance or strength , some due to total reworking of parts that look similar.

the lipo battery holder took me a while to design and required changes to the chassis to make it work.
i changed from NICD to LIPO for the weight savings and also to center the weight more to the center of the chassis. that change cuts 1/2 pound off the final weight.
the chassis changes meant also moving the servos back and fixing clearance issues.
the big chassis change was going from negative to positive castor.

during testing i found the inside rear tire would lift, i thought this was a bad thing but turns out that it is a REALLY good thing for FWD handling. some of the lift was due to a clearance issue which i corrected.

the front end got a bumper and additional beef ups for strength, i needed to re-clearance areas for the steering system. and the steering linkage changed from a spread to a center pivot design.

everything is intertwined so a small change must ripple through the design. also some parts had to be changed due to print quality on output. some things do not translate well when printed so that has to be taken into the design as well.

i'm working on the body which required me to change the motor mount design and drop the motor 2mm to get clearance.

i'm currently starting to output the newest version of the chassis.

as an example of me working on the 3d model all day based on a test print. in the photo above the Lipo battery holder design was to weak and required redesign in various places.

I had to perform maintenance on my 3d printer, replacing some worn out parts and cleaning and oiling everything.

as for testing it is now set to rain for the next 2 days heavy. then its suppose to go from 50 degrees down to 10 by sunday... so it will be quite sometime before i can get anymore testing then the bench..

oh i also purchased a SkyRC corner weight chassis balance and scale setup so i could get a accurate reading on the weight distribution and how much down-force is on each corner.

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Re: 3d printing fun. trying Postimage now

Post by XLR8 » Sat Jan 13, 2018 3:26 pm

Wow, a half pound is an enormous weight reduction. I wasn't aware that there was so much difference between the battery types. That alone will certainly affect handling.

"during testing i found the inside rear tire would lift, i thought this was a bad thing but turns out that it is a REALLY good thing for FWD handling. some of the lift was due to a clearance issue which i corrected"

Is this partly due to the chassis roll affect that results from castor combined with the square profile front tires? In other words, while steering the car, because there is castor, the front tire will roll onto its squared edge and lift that side of the chassis. I can't recall but are you planning any kind of suspension... at least for the rear of the car?
BITD, our Wednesday night races were on oval (dirt of course) and one class was for sprint cars. These were predominantly just converted RC10's. Some of the racers (1:1 sprint car race fans) would intentionally "stagger" the front-rear left-right spring loading to make the inside front tire lift in a turn. Although it looked true to scale, it wasn't the fast way around the track since the cars tended to understeer even with both tires on the track.
Anyway, it's interesting to see and I hope your weather changes soon so you can run the car on the driveway perhaps.
Doug

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Re: 3d printing fun. trying Postimage now

Post by RC10th » Sat Jan 13, 2018 3:40 pm

Looking good

but...........

images-39.jpg
images-39.jpg (7.81 KiB) Viewed 58 times

:lol:
I was old school - when old school wasn't cool !

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tamiyadan
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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Sat Jan 13, 2018 8:41 pm

RC10th wrote:
Sat Jan 13, 2018 3:40 pm
Looking good

but...........


images-39.jpg


:lol:
and yet everycar 1:1 is now pretty much FWD :)

"I can't recall but are you planning any kind of suspension... at least for the rear of the car?"
no this was intentional. the chassis is also structured to act like a suspension and is tunable based on how much infill and they type of pattern you decide to use.
example the front end can be 100% infill and the rear can be 10% infill on a honeycomb pattern. this allows the rear to flex, I also moved the rear mounts into arms that flex and you can tune that infill as well. this is something you can not do with a injection molded part and where 3d printing can be interesting. it is also possible to mix more materials together.
example you mix PLA and TPU together and have sections that are rigid and flexible on the same part.

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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Sun Jan 14, 2018 1:40 am

AHAHHA its pitch black outside and 20 degrees but i ran the car for the first time outside.
it ran pretty dame good from what i was expecting.
it is pretty quick too. went straight and seemed to hook up and appeared easy to control at least in the tiny area i was in to be able to see the chassis.

REALLY good steering for a FWD. was 750 Grams (1.6lb) in current iteration.

no idea about the other measurements until my scales show up.

i figured i had to get some quick run in before i froze to death.

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Re: 3d printing fun. trying Postimage now

Post by XLR8 » Sun Jan 14, 2018 4:36 am

Using the unique characteristics of 3d printing to vary the amount of flex in the chassis is pretty clever.
Well, the car keeps looking better all the time. What body are going with?
Forecast here is for 8 degrees Tuesday night.
Doug

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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Sun Jan 14, 2018 4:57 am

i have a newer version of the lipo battery box coming out at the moment.
i beefed up the design again a little more.

The chassis is all new again outputted today. after it came out i made another revision for the future. it gets better each print i learn from mistakes.
the chassis had me changing the servo position and revision for the lipo battery box the bumper is new as well.

i don't want to spoil the body surprise, plus its really difficult for me to create so i don't want to promise and not deliver lol

non of this is my original plan for anything i just went with it.

I plan to use the body to stiffen some areas of the chassis i don't want to flex instead of building an upperplate.

i do want to test it properly just not going to happen any time soon.

I have a lambo and 934 i need to run also and the weather has sucked since nov.

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Re: 3d printing fun. trying Postimage now

Post by tamiyadan » Sun Jan 14, 2018 5:11 pm

run #2 was about 5 minutes before i froze my butt off.

It actually runs really well.
my comparable is the Tamiya RM-01

1) it is faster then the RM-01 which is no real surprise because the gearing is slightly taller 4.3 verse 4.5:1 and the RM-01 is using a 380 motor while the FWD is using a 540 RSH both cars are using 6.6V LIPE Batteries. but i'm using a 2200 on the FWD which is about twice the weight of the RM-01 1100mah battery. I did this for 2 reasons 1) higher amp requirements of 540 motor and i wanted counter balance weight to the motor.

2) steering, REALLY good, really stable also. there is understeer but nothing like i would of expected. very controllable.
at high speed it feels much more stable then the RM-01 cars.
brake hard punch it through the corner and you have no worries about the rear end breaking loose because you cannot spin out.

3) straight line acceleration good, a little bouncy since there is no suspension, slight wheel hop but good otherwise. a little wheel spin very little, this could change since it is like 10 degrees outside anyway. in the summer on hot pavement it will hook up better.

4) problems. the center chassis flex is effecting steering slightly this can be solved 3 ways. 1) i can increase the ribs i made on the chassis to make them higher towards the front end this will stiffen from the front gear box to the servo. 2) or when i design the body anchor points i can have it lock the front and center of the chassis together. 2 might make things too stiff and increase wheel hop at the expensive of removing the steering flex issue. 3) design a center upper deck to act as a spin. this will reduce front to back movement from the servo to the front gearbox but allow diagonal flexing.

The bumper is too low and slightly touching the pavement. there is flex in the bumper on purpose, i lowered with additional 2mm clearance because i wanted it to flex up in a crash. and i also lowered it to give the body i was designing more room. solutions 1) design the bumper into the body no chassis bumper. 2) raise the bumper slightly and take some space from the body back.
the bumper rubbing is the most minor issue.

still need weight information feedback. and once i get everything the chassis needs then start to cut weight from parts where possible.

well video eventually. :(

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