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Thread: project ratrod pro-stock (unnoficial entry)

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Old 10-15-2009, 12:07 AM   #1
Rock Crawler
 
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Default project ratrod pro-stock entry

after seeing this contest, i got more excited about a project than i have in a long time. however, that was short lived when i read that i needed to be a member since april 10th 2009. kinda bummed i decided, what the hell, i cant win anything but itll still be a bunch of fun. so this is my non entry into the contest. ill still follow all the rules i need, i hope i can be included, just not actualy win anything (not that i think i will).

so here it is. ive had this car for a number of years, its technically brand new and never run, although ive tried building it in several different configurations. this is an original parma goodtimes '29 ford. this car is at least 15 years old. when i was given my first real rc (a now vintage tamiya buggy) when i was 10 i saw this in the hobby shop and thought it was so cool and wanted it so bad but never had the $129 for it. 12 years later i was in the hobby shop, now having many years of rc under my belt, and they had assembled the car and it was still for sale. after some haggling i ended up paying $50 for it as a rolling chassis. at one point it was 99% ready to go, just needed a stick pack. after more time on the shelf i decided i was going to turn it into a 12 cell drag car. i had it half together and it ended up back on the shelf. now, its back on the bench and getting built like i never thought of before.

here is what im planning
-12 1800 nicd sub c cells
-brushed motor between 6 and 10 turns, may handwind an old integy lathe motor i have.
-microswitch, no esc, just like the old school rc drag cars. i may do twin microswitches, from past experience single microswitch wired for brakes will make a 2wd car swap ends when you let off the throttle. (basicly full throttle or full brake, nothing between)

the biggest thing is simple and cheap. its a cheap chassis, i doubt itll get much use and i dont want to take much out of the crawler and savage budget. planning to spend a max of $100 and use mostly stuff that i have around, and my own creativity. that being said, project ratrod is a fitting name. it wont be the fastest, it wont be the coolest, but its gonna be a pile of fun

now down to buisness. i started tonight by stripping what was left down. i started with the rear axle. the drivetrain in this car is just like a pan car, and something originally designed for a closed endbell 27 turn motor from the early 90s just isnt gonna cut it.

what i did was remove the balls, drill the hubs, thread one side and bolt the spur gear directly to them, and the hubs together. what i now have is a spool.

the one hub that transmitted power to the axle (it drove the left wheel, the right was driven through a hub that just rode on the axle) was just lightly pressed on. that itself wouldnt hold up to 14.4 volts full throttle launches. i drilled the right side hub through the axle and threaded one side of the hub. itll be much stronger now.

im needing to figure out the front suspention now, or lack there of. this chassis uses a king pin design, itll work ok for what im going. the biggest thing is i need to increase the castor. a 1:1 dragster runs about 30 degrees castor, thats about what im aiming for. for those who dont know, castor is the angle of the steering axis from perpendicular to the ground. the more caster you run, the less steering response you have. in something im trying to make go stupid fast in a straight line, lots of castor is a good idea. this is the next thing i need to tackle, at least after getting some bearings for the front wheels and rear axle.

Last edited by Sharkey; 10-17-2009 at 07:41 PM.
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Old 10-15-2009, 12:21 AM   #2
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Well it looks like your on the right track. Lookin forward to see how the build goes.
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Old 10-15-2009, 06:57 AM   #3
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love your attitude. and good to see folks getting excited about building.
looking forward to seeing more
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Old 10-15-2009, 03:05 PM   #4
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i got good news for ya. talked it over with jason and we both loved your attitude, and its obvious you didnt join just for the contest.
so were gonna make an exception for ya, get yourself a star and your welcome to officially enter the contest and be eligable for prizes, fame and bitches. ;)
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Old 10-15-2009, 08:33 PM   #5
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ausome, thanks guys, really apreciate it. ill be getting a star right away.

picked up a couple things today. went into the hobby shop to get some bearings to replace all the ozite bushings (anyone remember when rc cars used to use bushings???) and they had a barley used peak 8 turn double for $20, so i now have my powerplant. i still need to pick up a second microswitch, and need to track down a couple more bearings as 1/8"x5/16" flanged bearings dont seem to be very common any more.

may have some more updates later.
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Old 10-15-2009, 10:24 PM   #6
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Sharkey, go to Avid RC and get those bearings for $1 apiece. They are from Houston and you should get your purchase within a couple of days.
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Old 10-16-2009, 12:27 AM   #7
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the only problem is me being in canada by the time iget them the contest would be over lol. i have another hobby shop to try tomorow
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Old 10-16-2009, 06:32 AM   #8
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LOL, yeah, that's a problem. Sorry, I confused you with another sharkey from a San Antonio forum
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Old 10-17-2009, 11:34 PM   #9
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car is coming along nicely. i spent half the day working on it and got a fair bit done. the motor is now in the car, along with the microswitch, throttle servo, steering servo, the wiring is all done, and the steering linkage is half figured out. i ended up changing my mind on the dual microswitch idea, instead im using a large resistor (25 watt .67ohm) on the single microswitch to tame the brakes down. im not sure if it will have enough brake with this setup however an 8x2 turn stops instantly without a resistor so it would without a doubt enter me for the carnage award. after some research i decided not to bother with adding castor.






i need to get some 4-40 threaded rod to build a drag link for the steering. im unable to find any 1/8x5/16 bearings anywere locally so i may have to put in an order online. if i end up doing that im going to order the larger parma hemi coupe tires (3" diameter 2" wide) and some o-ring style fronts. not 100% sure about the body, i may change it, i may not. im hoping to get the steering finished tomorow and make some 6 cell test runs.

now for some bad news, i had built packs years ago and they only had a couple uses on them, i was planning to use them for this. even though i stored them with 1/2 a charge in them they still were completly dead. i was trying to bring them back to life slowly and i think a cell vented (see my post in the electronics section for more info). if the pack is junk im going to have to replace all 12 cells (they are now hard to find 1500 or 1700 sub c nicd, not 100% sure) and thats going to throw me way off budget. that being said, i may have to drop to sportsman.
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Old 10-18-2009, 01:17 AM   #10
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cool build, hopefully we can all run these together at mission..hope you get your battery issues sorted out..do you want to run a 12cell setup for weight
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Old 10-18-2009, 02:02 AM   #11
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im planning to run 12 cell because i have them lol. i dont have a lipo charger and lipos are out of the budget anyways. 12 cells weight a pile, but i think i can make the weight work for me. i have 2 6 cell packs that are 4 cells on the bottom and 2 on the top. my charger only does up to 8 cells, so i guess if i had to i could find the bad cell and build an 8 cell pack, although that might put me at a bit of a disadvantage in pro-stock only running 9.6 volts.
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Old 10-18-2009, 08:46 AM   #12
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ive got a brand new set of parma hemi tires id sell ya.
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Old 10-18-2009, 01:34 PM   #13
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Quote:
Originally Posted by Sharkey View Post
im planning to run 12 cell because i have them lol. i dont have a lipo charger and lipos are out of the budget anyways. 12 cells weight a pile, but i think i can make the weight work for me. i have 2 6 cell packs that are 4 cells on the bottom and 2 on the top. my charger only does up to 8 cells, so i guess if i had to i could find the bad cell and build an 8 cell pack, although that might put me at a bit of a disadvantage in pro-stock only running 9.6 volts.
well if we do get to meet up and run together im sure i can let you run 3s or 4s lipo..heavily wrapped in foam..not sure if the reduced weight will hurt though..maybee good to have the car weighed down in the right places..i guess thats another use for stick on lead..if you can figure out how many amps you need i can probaly come up with a batt
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Old 10-18-2009, 07:28 PM   #14
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would be ausome to try on 4 cell lipo, however i am concerned about not enough weight.

so after some more work today i got some test runs in, i doubt i broke 30mph lol, but i did learn a lot. first off, my 1500 6 cell packs are toast, after cycling them several times i tried on 6 cells and it was pathetic, voltage would drop to 1.5 volts at the hit of the throttle and slowly recover to about 4 volts. i tried on 12 cells, i may have hit 25mph. i had a 2700mah 6 cell pack i charged up and tried, its nuts. im going to try to find another one of these.

so here is what i learned today
-if your going to run a bec be sure to check your battery voltage under load after each run. i had a run away because of this, luckily it was in my garage and the car went 5' before hitting the wall, no damage was done. what was happening was the voltage was dropping too low at the hit of the throttle with the car on the ground (in the air no issue) and the throttle servo would stick wide open and i lost steering. even though im going to run packs with decent capacity now im still going to run a 4 cell receiver pack. id rather be safe then sorry, a car with this sort of power/speed will do some damage if i lost control

-castor, it needs it. the reason i couldnt get going very fast is one slight steering input and the car spun right around. im sure the dusty/dirty road didnt help, but its obvious the steering is far too touchy. i also need to move the weight farther back, the receiver pack is going to be moved behind the rear axle.

-single microswitch, im still up in the air. an esc would be the best, but there are only a couple that would work (holmes hobby, novak super duty) and i cant justify the prices for this project. the problem with a single microswitch is without a resistor anytime i let off the throttle the car swaps ends, with a .62 ohm 25 watt resistor i have no brakes. i think im going to redesign my servo/switch mount plate and run duals. st least with duals if i dont have enough traction i can "pedal" the thing to get it going.

i built a wheely bar today for it, looks kinda cool but thats all it does at the moment. i think once i move some weight back in the car i may actualy need it.
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Old 10-18-2009, 07:32 PM   #15
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you need more mahs to help absorb the hit of the voltage when you stab it. 3000 minimum id say.
also try running some expo on your steering helps alot.
and be careful moving the weight back, it will make the car less stable at high speeds, and track worse.
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Old 10-18-2009, 08:04 PM   #16
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i have a 2700mah pack here already, im going to order a matching one. id perfer 3800, it would be better, but there was once a time when touring cars ran 6-8 turn motor on 2400s for 4 minute mains, so they should be good for 1 or 2 pulls before i let em cool and recharge. as for the steering issue, i did have the exponential cranked way up and steering percentage way down. the slightest movement and around the car went. i chalk it up to too much weight up front (the front end is actualy quite heavy), too wide a front tire (they are the parma goodtimes foams, 1 3/4" wide) and no castor.

im going to order a few things tonight, should i go with 1.5" front wheels or 2"??? looks like the pro-stock is the only rj speed kit to come with 2", the rest have 1.5"
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Old 10-20-2009, 08:28 PM   #17
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made some changes last night, but not liking it. i got another microswitch for the dual setup, unfortunetly the only switch i could get was larger than the current switch, and thats already too big. i re-designed the switch mounting plate and wired it all up, it works ok but im not happy with it. went back to the electronics shop with some part numbers and they are able to get me some small 26 amp microswitches for the end of the week. i have another battery pack being shipped, along with the 1/8x5/16" bearings, some front skinnies and a new set of rear tires i desperetly need (one almost brand new tire had a huge chunk fly off and hit me in the face when i was testing the microswitches on the bench. lesson learned, remove the pinion when testing). so for the most part, im waiting for parts. im going to re redesign the switch plate for the smaller switches, and i still need to get some castor into this thing.
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Old 10-24-2009, 03:13 PM   #18
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ok a small update. the new microswitch setup is in, batteries are remounted. had it out on the street for some testing and managed to melt a spur gear (honestly, thats the first one in 10 year of rc thats the first spur ive destroyed and no worn out). i happened to have an axial spur gear kicking around and wouldnt you know, it had the exact bolt pattern i needed for the spool bolts. tried it again and on 6 cells its hard to get going. what i basicly have to do is tap the throttle a few times to get it moving around 15mph then just hold the throttle. i didnt have the gps on it, but from what i know of my nitro tc3 (it was clocked at 65mph) i had to have been going at least 40mph within a couple seconds, and it was far from top speed. at an educated guess id say itll do over 55-60 the way it sits. i cant imagine it on 12 cells. i did get my steering a bit better by playing with the steering exponential on the radio. thinking about it now my radio has a panic steer button (when you dial the steering off you can use it to get 100% steering) so i should be able to dial the steering percentage down to make it less twitchy and still be able to turn around.
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Old 11-05-2009, 12:05 AM   #19
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i did some more testing on the weekend, i had it somewere around (at a guess) 45-50mph, it was far from top speed, and i still had the steering issues. the basicly anytime im on the throttle and give the slightest steering input the car swaps ends. im hoping a couple of changes that im making will help solve this. the biggest thing is the body, i now have a rj speed pro-mod body. i think that with any speed the 27 ford body just doesnt help give any downforce. the other thing is the rear tires, when i started on this project i had a tire fly apart on the work bench (hurt like hell when it hit me in the face, left a big red mark) and i had glues it back together for time being.

my parts finally showed up today after 2 1/2 weeks (stupid customs). i now mave my bigs and littles on it, i had to narrow the rear track up a bunch as the new rear tires are 1/2" wider. im planning on getting the body painted asap, im wanting to have it on the car before anymore testing happens, and im rather eager to try out my new airbrush on something other than paper and a scrap sheet of lexan.



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Old 11-05-2009, 10:27 AM   #20
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move your batteries forward 1.5" to 2" and limit your steering to 15 degrees or so.
moving the batterys will be the biggest benifit to stability.
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