speed runs ... 15t to 20t pulleys

[DKO]

Recently bought two E4tecs. One is Novak brushless. Looking to go fast. I realize that the easiest way to change the gearing is to change the spur and pinion gears which I've done. Right now I'm at 75s/35p, 69s/47p is on the way. Anyone upgrade their pulleys to 20tooth? If I upgrade to the 20t pulleys does anyone know what size of belt I will need and possibly where I can get it?
I've searched and search for this info to no avail. Thanks in advance.

[slowenuff]

I haven't thought to mess with the pulleys.

[DKO]

I think that changing the pulley size will make a bigger difference than changing the spur and the pinion. I ordered the plastic 20tooth pulleys today. Now I need to find the right size of belt. Can I just count the number of teeth on the original pulley and add 5 teeth? Or maybe I'll just guess at the extra length. Any idea how much adjustment room I have with the belts?

[slowenuff]

Well it depends on whether or not your tecs have gone through the nitro diff swaps.

[DKO]

Looks like I've got the steel yokes with the original differentials. I haven't had problems with them slipping. Is that the main reason people swap them out? Does it change the gear ratio as well? Thanks for your help.

[slowenuff]

The reason why we changed out the stock diffs is that they won't last long under brushless power. The weak point is the diff plate itself. The adjustment screw will eventually loosen and will begin to strip out the threads. Or while trying to tighten the diff you will accidentally strip out the diff plate.

[DKO]

Great info. Thanks, I'll change the diffs out as well. I just realized that I have bushings instead of bearings as well. I imagine that will make some difference in speed.

[slowenuff]

Definitely install bearings and do the diff swap. What kv is the motor you are using? And as far as battery selection most 3s 4000 lipos should fit the battery bay.

[DKO]

slowenuff,
Thanks for the battery info. The engine is a novak pro ss13.5. I think its 3000kv. Hardly fast enough for where I would like to go with this car. Hit 49mph using my phone gps attached to it. I'd really like to get a setup similar to yours (I saw it in the "Gearing" sticky thread). I think I need to sort out the small stuff then upgrade the esc and motor. What kind of speeds have you hit with 9000kv? Is your frame graphite?

[slowenuff]

I have no idea what speeds I have hit as I don't have a radar gun.Also I'm not ready to mount my evo or garmin on my 4tec. What I can tell you is that I haven't been able to go past half throttle. It's rainy season here so it will be a while before I can try again. I have chosen not to go with a graphite chassis cause I don't race and only do speed runs with it. Jump up to higher kv motor and you'll start to find aerodynamics your current obstacle. Find a low profile body like a vette or saleen s7 and don't cut out the rear wheels. Thats what im gonna try next as soon as a large parking lot dries up.

[DKO]

Let me catch up with you in the required upgrades area then I'll get a much faster motor for sure. I don't even have a body painted yet. I think I'll skip the graphite too. I can't blame you with not wanting to put gps on there. I cringe every time I see my blackerry go sailing across the pavement. It's been snowing some here in Indy so I haven't played with the 4tec just the mini revo. I got the 20t pulleys today and all of the other parts but one for the diff upgrade. Got the bearings too. I'd like to upgrafe one thing at a time then test it and see what make the biggest speed diffrence but I doubt I'll have time for that with the holidays. I'm sure the weather won't cooperate either. What kind of tires and rims are you running that will stay intact at those speeds? Do you have a slipper clutch?

[slowenuff]

I'm using parma foams but I also have a set of belted hpi x patterns mounted on hpi 12 spokes. I am running the older peg style slipper clutch. It will help extend the life of the belts and the stock diffs. Heres another build thread to follow to widen your 4tec.

[DKO]

Bought one of my son's a vxl stampede for his b-day so I haven't worked on the 4tec for a few days. I'm planning on a few days off over the holidays to get something done with it. I've got most of the parts of the slipper clutch on my other 4tec. maybe I can salvage it. Thanks for the link as I wasn't really sure where it came from. The rally car build thread was a good read. Thanks! I may widen it after I take care of the other details first. I realize widening it will help with the handling. Does it make that big of a difference with speed runs?

[slowenuff]

I noticed a change but using a gyro is even better. Widening will also allow you more choices of bodies.

[DKO]

Are the sway bars helpful?

[slowenuff]

Not for speed runs, more so for drifting or racing.

[DKO]

Got the bearings switched out and an RPM shock tower. Got the front differential built and in the car. Tore the back end apart, built the diff but have not installed it yet. This has turned out to be a bigger project than I imagined, not that I haven't enjoyed working on it, just a bit time consuming. I have not installed the sway bars. I think I'll get a cheap gyro later. I have not changed out the 20t pulleys yet either. I'd actually like to wait on the pulleys until I get a sense of how fast it will go with these upgrades. Then change later them to see if it makes any difference. Ordered 49t and 55t RRP spur gears today. I have the RRP 47t pinion ready to install. Any advice on the rear diff install and getting the belts to fit (or where to get bigger belts)? I read where someone renotched the bearing holder to allow more belt adjustment. Is this necessary and if so does it work?

[DKO]

Finished the diff conversion. I opted not to change the pulleys to 20T because they would rub against the motor. I didn't realize how limited the space is there. I think that space is better used for room to adjust the motor for different pinion and spur gears. One thin I am struggling with aligning the front tires straight. Any suggestions or links? Thanks in advance.

[slowenuff]

Use calipers while adjusting the front turnbuckles.

[DKO]

slowenuff,
Thank you. I did get the alignment straightened out. Now when I turn the steering the left it just stays left. I disconnected the right steering arm and it does the same thing so the problem is on the left side. Also when I accelerate I hear clicking sounds up front as if the stub axles are rubbing against the steering block/axle housing.

[slowenuff]

Check your servo saver to make sure it isn't stripped as well as the steering linkage for any damage. As for clicking sound check the bolt that connects the turnbuckle to the steering blocks. It may have come loose. When it gets loose the flat nut on the inside of the steering block will make contact with the axles. I recommend these as you wont have to worry about it.

[DKO]

Thanks slowenuff you're always spot on!!! The metal steering linkage that goes across the middle of the car was bent so the steering would stick on one side. The clicking was exactly what you said so I puchased the 4336x as you recommended and made some adjustments. It seems to steer and run well. Haven't road tested it yet(too much snow) but I put some nice long burnout marks across my wife's kitchen floor then I blamed it on the kids! They had already tattled on me though. Now on to the next upgrade for the car... Thanks again slowenuff. Your help is appreciated!

[DKO]

Made a brief run today on the street. It was very cold with icy patches on the street. 1st time with the nitro diffs. 41 mph (blackberry gps using northstar attached to car), only flipped once but really had a hard time steering. Slower than I hoped but I think a couple of factors may be slowing things down:
lack of traction (weather, worn road hawgs)
tight belts
not sure if the 3s battery was fully charged
need to work more on the alignment/setup
I wasn't running with a body either, not sure how much of a difference that makes

[slowenuff]

For shame.....always use a body. Road hawgs? As in 2.2 stadium truck road hawgs? Use foams then you won't have to worry about balancing issues.

[DKO]

I take it from your hints that my next upgrades should be new tires and to paint a body. I certainly agree. The road hawgs came on the car. I can't make up my mind on the tires. What size did you use 26mm or 30mm? What's the best shore rating for pavement that will last?

[slowenuff]

Foams will be the most economical as they come mounted on the wheels. $26 give or take for an entire set. Or you can check out hpi for belted tires.

[DKO]

Okay I went with the HPI 26mm pro comp belted tires and HPI black mesh 1mm offset wheel:
http://www.hpiracing.com/products/en/3711/
First time gluing a new set of tires, watched a few videos before trying but still put too much glue on the first one. Is there any way to clean the ca glue off the outside of the rim/tire? I tried to wipe it off while it was still wet but made a bigger mess. I think it would have been better to just leave in in a glob and pick it off after it dried. I just messed up one tire on the inside. The others look okay. Any suggestions?

[slowenuff]

This stuff works really well even after the glue has dried. Or you can use some acetone based nail polish remover. My gluing technique involves nitrile gloves, thick ca glue, debonder, a rag, and lots of q tips.

[DKO]

slowenuff,
What mods did you do to your battery tray to fit larger battery packs? I got some nail polish remover for the glue. Thought I would try that first since it was convenient. Just realized last night that my motor is rubbing on the front belt. I'm sure that's another reason it was running a little slower than expected. Know of anyone that makes a 48p pinion gear that's bigger than RRPs 47 tooth? I have several bigger spurs that I know will make it fit if not. Again your help is appreciated and your written conversation is enjoyed.

[slowenuff]

[IMG][/IMG]
I cut out the two chassis supports just behind the servo then used washers that were 3mm thick to raise the upper chassis. The battery is now held down by 2 zip ties.

The blue dots show the placement of all the washers I used to raise the chassis.

[DKO]

Thank you for the pictures. Did you place the washers on top of the bottom tray or on the bottom of the top tray. I hope that makes sense... Maybe it will be clearer to me when I take the car apart again. I understand that the blue dots are the placement of the screws that hold the top chassis on. Are any of the washers shown in the top picture? I realize your point with that picture was to show the removal of the braces and battery fitment, nice work. I thought about just raising the back of the top chassis by placing 2 washers in between the top chassis where it attaches to the motor plate (on top of and in front of the motor). I really like the lexan plate. You're very ingenious with these modifications. You should design the new 4tec for traxxas (looks like you already have). I'm betting your car will go 100mph or more. Do the HPI tires balloon at all with that much power? I really like mine. Thanks for the suggestions.

[slowenuff]

Sorry heres a better picture showing the battery bay and placement of some of the blue washers.



The lexan plate was more to help keep some of the dust and debris out of the gears and belts. And the hpi tires don't baloon.

[DKO]

Great! Thats very helpful. Did you cut your own spacers or did you buy them somewhere? Did you end up being able to use the stock screws on the bottom or did you have to get longer ones? I'm sure the lexan plate will help with aerodynamics as well especially at high speeds.

[slowenuff]

I bought them. 3mm countersunk. As for the screws some are slightly longer than stock. As for the aerodynamics it is possible the lexan sheet helps im not sure though.

[DKO]

The snow melted enough to make a few cold runs today. Things have slowed down a lot. Smaller tires and no balooning makes a bigger difference than I imagined (from 41 to 33 mph). Not exactly the direction I wanted to go. I'm sure the HPI tires had a hard time getting traction on the ice cold pavement as well. I did find an old body to run on it. It's more than ugly. I used duct tape to cover up the large hole from someone using it with a nitro car and the multiple small holes where it has been mounted on other cars.
I would definitely like to do the battery mod. I need to make a decision about either getting the longer but skinnier rear belt or notching it like SpyderMan1964 came up with. I'm leaning toward notching it as I like the wider belt. Next decision will be a faster motor. Novak makes a 3.5 turn 10500kv motor which would be fine but my Novak Havok esc is really made for 2S even though I run it on 3s. I'm expecting it to fry anytime. My preference would be to go with Castle with motor and esc. I'd prefer to buy a used one to avoid the expense.
I ordered the rear aluminum hub carriers TRA4352x. They are apparently on backorder. The front ones don't hold the bearings tight enough as there is significant wabble in one of the wheels. I checked everything else for fit and made sure everything is tight. The plastic ones were a nice tight fit. Is there an easy fix for this?

[slowenuff]

Well used mambas should be in plentiful on the web. But if you buy new get the mamba pro 9000 combo. The esc is capable of 6s though I wouldn't use 6s on that motor. Does the bearing easily slide in and out of the carrier? Post a pic if you can.

[slowenuff]

Almost forgot you can get the original mamba max with a 9000kv motor for $150. The esc is rated for 3s but the motor is rated for only 2. But the odds of getting that motor to its limits are highly unlikely.

[DKO]

My camera is on the fritz so pics aren't easily accessible at this point. The bearing is such a loose fit it falls out. I thought about using some blue loctite on it but I thought sure enough if I did that I would have to take it apart and I wouldn't be able to get my bearings out or I would ruin them in the process. Should I just put a small piece of tape in their instead just to make it snug? Considering the expense of the carriers I expected a better fit. If the rear ones are that poor of a fit then I may just return them and keep the plastic.
Is the Mamba max programmable via computer as well (not that it's necessary)?
Going back to your previous post where did you find spacers like that?
I'm glad I got the car out for a few minutes yesterday as everything is iced over today. Thanks for all your help.

[slowenuff]

Hmmm so one wheel wobbles alot. Try swapping the wheels around on the front axels and see if the wobble is still there. Im at work right now so I can't look at mine as a reference point.

[DKO]

Great idea! I'll give it a try and report back.