50 mph.... how to get there

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LLkoolskillet
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50 mph.... how to get there

Post by LLkoolskillet » Sat Jun 16, 2012 10:55 pm

*EDIT* Since this thread is now super long and it seems to catch a lot of views still. Ive started a new thread about my goal of 65mph and beyond. Now I have a purpose built truck. Heres the link :twisted:

modules.php?name=Forums&file=viewtopic&t=96702

Plain and simple 50 mph in a savage is extremely hard to achieve. I will say it right now, if you have a claim you better show proof, if not shut the **** up. Im not writing this to say hey ive done it look at me. Im writing this to discuss the many variables that go into making a savage hit that magic number.

So what are all the variables needed to make it?

Motor
Tires
Gearing
Weight
Clutch
Chassis
Suspension
Fuel
Glow Plug
Air Filter
Ambient Air temp
Humidity
Distance from Sea level

All these things play a major role in achieveing this goal. I know there are a few of us here that are actively trying to achieve this. I can honestly say it MUCH MUCH harder than one might think.

In my case, gearing, chassis, and wheels have played the biggest role in my quest. Lets think about this; the longer XL chassis and killer as it is. Is it really the best choice? Maybe... with the right motor and weight reduction involved its possible. The X chassis is shorter and lighter off the bat making it an easier choice. My truck fully loaded weights 12lbs, in XL fashion. My fastest recorded speed was with the Phaultines. Yes I am running double belted Bowties currently. Heres the odd part, you would think a larger diameter tire would have a higher top speed. Well in my case its the opposite. Im stumped :x Im thinking about swapping back on the GT2s, silly I know but there super light weight and frankly ive seen some crazy speed out of them.
Robin recored his with 17/47 gearing, im running 20/47. This is why I think tires choice is crucial here. The larger the diameter the faster it will go. But remember weight is also an issue. Terra Pins would work great but I dont have any, thus why the GT2s.

Your Glow plug is not going to give you an extra 10 mph but it will allow you to run a bit cooler on top allowing you to lean it out just a tiny bit more. This is a cold plug of course.

Fuel... dont bother on 20-25% IMO 30% is where you see the most gain.

Temp and humidity play a major role in your tune and we all know this when tuning from running around noon to then running in the evening. Your tune has completely changed.

Your clutch imo must be up to the task, IE: not some plastic clutch, beacuse there is going to be a lot of heat generated from trying this, esp with tall gearing, So aluminum is a must

Suspension should be tight cause you dont want your truck bouncing all over the place, that would result in loss of power or crashing
Last edited by LLkoolskillet on Sat Nov 24, 2012 12:49 am, edited 3 times in total.
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Post by bigbigbrig » Sun Jun 17, 2012 12:01 am

Being that this is a discussion I beleive I will start.
I will just go down the list.

-As for the motor I assume everyone will agree with me that an ERCM modded picco with an ERCM pipe will be the power plant
-Tire, I see that you are using phautlines. Have you given any thought to 40 series road rage tires on dish wheels. It may be lighter.
-Gearing, has anyone looked into the complete delrin trandmission and spur gears. Again weight.
-Weight, If its just speed you ar looking for you don't need a center skid, bumpers, roll bar/engine protector, lock the rear plastic hubs and lose the rear turnbuckles, humppack over the 4aa batteries, and the ofna tank mod(don't need a big fuel tank for a speed pass)
-Clutch, I have seen a lightweight clutch on ebay a few time, less rotating mass on the motor,
-Chassis, Carbon fiber LCG
-Suspension, Hpi sway bar kit, and 4 rear buggy shocks would get it low and handling,
-Fuel, Byron 30% race blend
-Glow plugs, I would think you would want a turbo head and an O.S. turbo plug,
-Air Filter, Motor Saver filter.
Ambient Air temp-my turbo'ed VW runs best about 60F so to me that would be a good starting point.
Humidity-the lower the better
Distance from Sea level-closer to sea level the better

This is just what I think would help in the 50mph goal.
Thought it might get the ball rolling.

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Post by Dcdoode7 » Sun Jun 17, 2012 12:41 am

You tease us LL. what is your fastest recorded speed and your goal speed? I'll guess 60mps

I think the CF chassis will help a ton with weight. I would think that the XL chassis would be my choice due to the wheely factor.

Also, what is the distance you plan to do this in? Obviously the range of your Tx, but how far is that?  I saw a video of an e-revo (I think) doing highway speeds somewhere in BC, and the guy was chasing/taping in a 1:1 full sized car. It was incredible. I'll try to find that one later.

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Synk
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Post by Synk » Sun Jun 17, 2012 12:55 am

Dont overlook the body type. A gmc topkick is not the right choice. Needs to sit low and be vented at the rear to remove any parachute effect.
Ceramic bearings are lighter with less friction.
Midtank can be lighter with better areo
2 wd remove 3 dogbones and a diff
buggy tires up front.
But then is it still a savage?
savage x ss Lrp zr.30, octane cage and mod radio box, ofna mid tank 250cc, integy saver front/rear hubs, sv250 mod 3 spd, no mix arm throttle, hitec 5645 5625 servos, 4xbb 4xstd shocks w/35wt, flux drivetrain, 30k wt diff oil,  new era wing, tonys screws

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Cadimman
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Post by Cadimman » Sun Jun 17, 2012 1:16 am

Taller tires have to make make you go faster unless something is lagging. Engine, clutch, etc. it's simple math unless your larger tires weigh too much.
Thanks to all the GOOD people on this site!!

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Post by Sharkey_t » Sun Jun 17, 2012 2:03 am

imo tires are the biggest factor. trying to turn a heavy tire is going to kill any speed. also tread design is a big factor, a knobby tire is gonna kill speed as well. i saw a set of mt sized foam tires, they were mostly wheel with a thin bit of foam (like a touring car tire, just bigger), i would think those would be the best bet, or just run 1/8 scale buggy onroad foam tires. foam tires will remain stable at high speeds and they dont balloon, and will give optimal traction.

getting the weight down in the truck will help, however its not the biggest factor. rotating mass is the biggest deal, the rule of thumb in real cars is losing 1lb rotating mass gives the same gains as 2lbs static weight. getting the weight down in the tranny may help, however you still need to consider durability. i think the best way to go about losing weight in the tranny is to loose the tranny completely. ofna makes a 2 speed for the buggies, get one of those and drop it in, itll be far lighter and less drag. i dont see much else to cut weight, not unless you start shaving plastic were it isnt needed.

also consider at what point it isnt a savage anymore. much past changing to foam tires and a more aerodynamic body your starting to lose what makes a savage a savage, and thats a multi-purpose truck that you can beat the snot out of and it still comes home in one piece. imo, to purpose build a savage for top speed is kinda pointless, sure you may have the fastest savage, but it still slower than 90% of the touring cars are out of the box.

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Post by dragonbat13 » Sun Jun 17, 2012 3:01 am

LL for your set up you need to loose the heavy tires.  Imagine trying to spin a big heavy mudgrip on a ten speed bicycle.  Now imagine a same diameter correct ten speed tire.  The tiny thin tire is going to use much less energy to spin.

Also a narrow tire along with x width and zero offset wheels will help some also.  Keep the xl length.  

a good aerodynamic body would help.  especially if something could be found to cover the wheels.

If the two speed is the same final ratio as the three, stick a two in.  Better yet, if you could figure out how to only run the third gear set in the three speed with the clutch locked out that would be best.  

You can go too tall of a final ratio at the tire.  If you get too tall the engine wont be able to hit max RPM.  Doesnt matter who modded it, if your trying to make the engine do to much work than it just wont work.  What I am getting at is that it needs to be tuned to the RPM window at the speed you are looking for.  Set a goal of 50 and try to get the engine at the correct RPM in final gear when the wheels should be turning enough to be at 50.  Dont set it for something like 75 (which you know the engine will probably never do) expecting it to get up to RPM to hit 50.  That would be overtaxing the motor.

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Post by ChrisX » Sun Jun 17, 2012 4:07 am

i have had 43mph with just a set of phatlines and 17/47 gearing and a 2 spd box. however now i have had some improvements, i am fitting my modded 3spd, i have CF tvp's and pins and so when i am back on the street i will get a vid and see what i am reaching then.
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Post by nitronly » Sun Jun 17, 2012 7:50 am

I have an ercm picco with "top end" mod and side bleed, bullet proof 3 speed and 18/45 gearing but will probably go up to 20/45 for the speed runs. I will be getting all my carbon fibre goodies from prc next month. I'm thinking of running 3.2'' road rage on dish wheels. 55 mph+ is my goal.
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Post by Beavinator » Sun Jun 17, 2012 7:58 am

Yes I totally agree that its the big tires that are holding you back.  Screw the ceramic bearings, I dont think they would make enough difference to justify the cost.  Just make sure you have good bearings that are oiled up.

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Post by LLkoolskillet » Sun Jun 17, 2012 8:27 am

Awesome this is just awesome :D

Check it out, my current setup has some weight saving in it but where I shaved the weight I added it back with custom pieces

I don't run a plate up front, like the FLM one. I use plastic servo mounts I made. The front and rear ends are stock except he aluminum towers. Even the chassis braces are plastic. Where I add the weight back slightly is the rx/batt box I made. But I would figure it weights as much as the stock one with all the electronics.
My wheels are pretty light but I do have a set of Nubz off the Hellfire. Pretty darn light, Infact there the lightest wheel I have. I use the Losi 8 2.0 shocks with red hellfire springs and there setup to be stiff just like a race car. When I turn sharp the opposite side lifts up in the rear.

Im 65 ft above seal level
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Post by nitronly » Sun Jun 17, 2012 8:46 am

I'm 780 ft above sea level. I'm getting the werks 4 shoe clutch. I will be using this in place of the stock radio box.       http://www.platinumrcproducts.com/prc%20112.html
I'm mounting the steering servo underneath with flm mounts like on my midtank and will find a small battery/reciever box to mount on top next to the throttle/ break servo and I'll be running an ofna 125cc tank mounted in the stock location.
I'm also using prc std length lcg chassis, prc bulk plates, prc engine mount, prc lcg shock towers and some Kind of buggy/truggy shock?

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Post by LLkoolskillet » Sun Jun 17, 2012 10:02 am

So how much speed is there to be gained from adding 2 teeth to a cb?

IE: 18t going to a 20t

Today I'm thinking about trying a few different variants.

GT2 wheels
HPI Nubz wheels
Paultlines
17t, 18t, and 20t CBs
Maybe swapping out TVPs for the X ones
Cold glow plug which will allow me to lean out the top just a tiny bit more maybe an added 1mph

Today the temps are much cooler so I'm hoping for a larger gain in HP. Not much but it's more HP than on a hot hot day at least.
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nitronly
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Post by nitronly » Sun Jun 17, 2012 11:22 am

What are the temps like where you are LL? We get anywhere from 15c to 30c this time of year here in winnipeg. My ercm lrp only gets to 205-210f on a  20c day when running it hard, this is with an mc-8 plug. Light bashing will stay around 180-190f in the same weather. I haven't brought out the temp gun on a 30c day yet. My picco gets up to 200f pretty easy but thats because the pinch is still tight and i'm still breaking it in and running an odonnell hot plug.

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Post by dragonbat13 » Sun Jun 17, 2012 11:38 am

you wanna try something on the cheap,  get some stock wheel bearings, pull all the seals out, and put some sewing machine oil on them.  Make your pass and see if the MPH increases.  The bearings would probably be trashed after a couple runs, but they would probably run fairly fast for stock bearings.  Sure would be cheaper than ceramic boccas (or however you spell those two hundred dollar bearing sets).
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Post by nitronly » Sun Jun 17, 2012 11:54 am

The set I almost bought was over $300 for abec 7 ceramic bearings. :roll:

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Post by LLkoolskillet » Sun Jun 17, 2012 1:15 pm

:mrgreen: I did it!!! :mrgreen:

Temps outside were 74f, the temps on the motor were 265f ish As you can see I used the Truggy Hellfire Nubz wheels with a 20/47 gearing.
I kept the medium plug in, used Odonnells 30%, ran with NO body. Basically the only thing I changed was the motor and wheels. Everything else stayed the same from yesterday. The Picco I used has 10 gallons thru it :twisted: surprised the heck out of me, it sure did

Oh and I used the $12 integy clutch kit
Last edited by LLkoolskillet on Sun Jun 17, 2012 2:06 pm, edited 2 times in total.
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Post by LLkoolskillet » Sun Jun 17, 2012 1:56 pm

Feast on this gentlemen..... Please excuse my language as I was excited

[YouTube]
[/YouTube]
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Post by [CH3NO2] » Sun Jun 17, 2012 2:10 pm

Yep, as you found out, it's possible to hit 50mph with mostly stock suspension/chassis geometry, and a powerful engine with proper gearing. Here's a video of a stock Savage XL with a modified Picco 28 and 086 pipe hitting 51mph.

[youtube]
[/youtube]

I'm pretty sure purenitro had an even faster 53mph run a while back as well.

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Post by LLkoolskillet » Sun Jun 17, 2012 2:30 pm

His was 52.9mph, my goal is 53mph hehe. There are a few other things I can try to gain an extra 3 mph but that's for next weekend.
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