1/5 scale motor in Slash 4x4

[Gunner1]

Question on the bearings. The ball bearings we use are not designed to have much of a side load. When you did the mod to tighten up the slop did it preload the balls. Usually a zero play bearing is a tapered roller not a ball race. I am looking at bringing it down to a couple of thou but zero seems tight for 100+ runs.

[shack351]

Hey Gunner,

I agree with you 100% about the side-load. And good question. Let me try to elaborate. The way we adjusted the "2mm" spacer was really just getting things the way they should have been in the first place. I don't have the exact spec at the moment, and I celebrated Cinco de Mayo a little bit, but I can definitively say that the outer spacer was too wide, closer to 2.25mm. We started by removing a small amount of material, then reassembling and measuring. After several subsequent dis-assemblies, machining, re-assemblies and measuring, we got it where it fit best in my particular stub axle carriers. As a testament to Traxxas' consistency, all four sets of rear stub carriers I own were nearly identical. This ended up being very close to the 2mm that the spacers should have been from the factory.

With that being said, the entire load on the bearing, when tightening the hex, or in my case, the barrel nuts, does not apply any abnormal pressure, or load, to the bearing. When the unit is completely assembled, all pressure emanating from the barrel nuts is transferred through the inner race of the outer bearing... to the outer spacer... onto the inner race of the inner bearing & spacer and then finally that pressure is contained by the inner bearing race landing on the MIP Keyed Axle (#10131) The radial plane of the bearing still rest as it should, without bind, in the carrier, and the outer race just sits snug. I think the reward is worth the time spent!

-Shack

[riderinblack]

Oh man! Awesome build you have here! I just did 23/52 gearing on 4s and I thought that was insane on an 8th scale system but this.... This is just Ludacris!

[Trentbaby65]

Oh man! Awesome build you have here! I just did 23/52 gearing on 4s and I thought that was insane on an 8th scale system but this.... This is just Ludacris!

I agree mate. I have no interest in setting speed records myself. Just a mechanic with a race car background, but I'm riveted to this build and thread.
Can't wait to see where it all goes.

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[shack351]

That 4 px is the only way to go. A real good choice there.


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Hey Magnum,

Yeah, I am really digging it! I spent many hours this weekend trying to dial it in. The granularity has seriously impressed me. It is pretty much everything I wanted in a radio, except a few more channels would be nice (7PX?). My other "RC time" had me working on my oldest son's Slash. I've been trying to get him more involved in the building process but he just doesn't have the patience now. So... I ended up doing most of it, which is fine because I love to do it! I don't think he's done adding stickers to it but as you can see below, he wants everyone to know it's a TRAXXAS!

I think I have found a decent place for a few speed runs but it will have to be done at night. I have driven the road and will need to walk it to remove a few small pieces of debris I saw and double check for other potential hazards. I'm gonna take her over there tomorrow night for a quick test of how well I can see it while lit up with LEDs. This may not work... at all, but it's 5 lanes wide with lots of HPS street lights. I'm desperate for a good place to open it up!

-Shack

[shack351]

Hey Rider & Trent,

Much obliged! Once I felt the need-for-speed... I was hooked. Things are not moving along as fast as I'd like simply because I can't find a place to drive it. As I mentioned above, I found a night-spot but that is questionable. The airport I found is the best place but, as luck would have it, now is the beginning of their busiest time of the year and getting in over there will be difficult. I'm sorry I do not have what we all want to see yet, but I think it will be worth the wait. Whether it's moving and grooving or crashing and burning, the footage should be something to watch.

-Shack

[Trentbaby65]

No need to apologise for the time taken mate. Most of us have other stuff to do as well.
Love the approach you're taking with this. Death or glory it's sure to be a great adventure. I suspect from your thoroughness that glory awaits.
Good luck and cheers from Oz.


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[shack351]

No need to apologise for the time taken mate. Most of us have other stuff to do as well.
Love the approach you're taking with this. Death or glory it's sure to be a great adventure. I suspect from your thoroughness that glory awaits.
Good luck and cheers from Oz.


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Thanks for the vote of confidence my friend! I appreciate it. I just hope that the old adage "good things come to those who wait" is real!

-Shack

[shack351]

Well, the speed rig is totaled. Just kidding, but I did have something, um, unexpected to happen. I was heading out to give it a quick trip down an access road I spotted that looked like I might be able to get some good speed on (the night-time run I planned the other day was too risky). My children and a few other neighborhood kids were playing outside and saw me carrying the rig to the car. "We want to see it go... come on... please, please, please!!!" Ok, ok... hold on. So I pull the controller out of the case, turn it on and set it down to my left side. I then remove the body clips & body then connect the batteries to ESC. Here's the fun part. As I reach for the body, on my right, the car takes off in FULL REVERSE and slams into a lava rock in an island in front of my house! After I picked my jaw up off the ground, I look down and see my youngest son with the controller in his hands! Oh my god, what have you ....... So I remove the controller from his hands, walk over to the rig and disconnect the power. It doesn't look too bad considering it just slammed into a 75-100lb rock at 20+mph. It only went about 20ft or so before impact but it was moving pretty quick. Let's go inside now and look more closely at the damage.

It only takes a second or two to see that the left-rear a-arm is toast. It did not actually "break" anywhere and the wheels still turned freely. For this piece to bend and not break was actually nice to see. Many aluminum pieces will snap once they pass the yield point. This tells me that the tensile strength of the aluminum used in production of the a-arm is of a decent quality. And the piece was most likely machined with the front & rear sides across the grain. Aluminum will withstand a much tighter bend radii across the grain than it will with the grain. That is my guess as to why it bent like a pretzel without actually breaking.

I am actually surprised at the lack of further damage. The beefy HR bulk-head tie bar did its job and the modified rear bumper slowed it down a bit, too. After disassembly, there are a total of 4 pieces that have to be
replaced: The a-arm ($12), both hinge-pins (Titanium BTW - $5) and the carrier ($10). The bent outer hinge-pin prevents the carrier from being removed. I will press it out later and maybe use it as a backup for the bashers. The bulkhead hinge-pins holes did not look stretched or widened but I have another Traxxas 6829 bulkhead and also a Hot Racing LCF0901 aluminum piece that I may drop in it anyway.

I had to toss in a few pics for good measure. This is the culprit! His Halloween costume and expression were fitting here so I had to include. I told him to wear that outfit and stay in his room for six months! Obviously not... it was my fault for not having the controller in a better place. I got lucky this time with my wake-up call. Won't happen again though. I will be wearing that sucker around my neck from now on!

-Shack

[Trentbaby65]

Lucky!
Just remember to teach his kids, when he has them, how to break daddy's stuff. Haha

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[Squeegie]

Wow! Glad it hit a lava rock instead of one of the other kids!

[SL4SHGT8BASHER]

i've had my sons do the same thing more than once. you look away for a split second and those sticky hands get ahold of anything. love this build by the way. have a great weekend.

[Gripdog7205]

Sweet tat sleeves

[Miltdoggie]

Looking good shack!!!


Saw this online,

[Beefred00013]

I've seen my slash go through all these stages it's like history repeats its self over again



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[Beefred00013]

I can tell you all the wrong aspect in your build by the looks and all the extras that you really don't need


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[Beefred00013]

Another thing is you shouldn't worry about the scratches because at 50mph accident or flip over trust me when I say things are going to shave off metal or plastic


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[shack351]

Wow! Glad it hit a lava rock instead of one of the other kids!

Without a doubt! A couple of important lessons learned here. I already try to keep everybody clear but a few extra precautions will be taken from now on.

-Shack

[shack351]

i've had my sons do the same thing more than once. you look away for a split second and those sticky hands get ahold of anything. love this build by the way. have a great weekend.

Yeah, he was 10ft away when I last saw him. He snuck up and pulled a fast one on me. Thank you and hope you do the same.

-Shack

[shack351]

Looking good shack!!!


Saw this online,

Hey Milt,

Thanks brother! It is coming along well but proving grounds are my Achilles heel right now. Wow, that's a really nice build. Where did you come across that?

-Shack

[shack351]

Another thing is you shouldn't worry about the scratches because at 50mph accident or flip over trust me when I say things are going to shave off metal or plastic


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What's up man!

I hear you... definitely not gonna stress too much over a trashed body... got several of those to wreck!

As for the wrong aspect of the build, I am just trying to have fun brother! I am fortunate enough to have the forum here and the advice of a few engineers that I work with to help fill in some gaps. I know there will be failures but many can be avoided with some good forethought. We'll see how it goes!

-Shack

[Beefred00013]

Zip tie you wires down I tore my wires when I flipped my slash over


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[shack351]

Zip tie you wires down I tore my wires when I flipped my slash over


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Yes sir, I have a brace that hasn't been seen in pics here yet that I attach the motor wires to but you are right. I flipped my basher at fairly high speed and caused myself some wiring damage. It was repairable but a lesson learned... I hope!

-Shack

[shack351]

After seeing tire vibration issues at high speed, even after a basic balancing, a better solution was needed. I wanted a way to really dial-in the tires and my friend came up with a great way to do it. This is 100% his design and I think it is brilliant. I know that most people don't care about micro-balancing their tires but I thought I would share this piece of hardware.

Here is a short video of the device in use. I have put 15 or 20 tires in it so far and it is amazing to see the difference between the same type tires. One set of tires that I checked varied wildly from tire to tire in balancing and general "trueness". I will say that the XO1 tires looked pretty good. One tire in particular stood out as "off" but they were nice and round in general. I was thinking that the "thread" balancing technique was good but all the tires that I thought were balanced, the new device revealed they were not.

-Shack

[Miltdoggie]

Video is private, private.

[Squeegie]

Very nice nearly frictionless balancer!

to you and your friend!

[shack351]

Very nice nearly frictionless balancer!

to you and your friend!

Thank you, sir. Yeah, we wanted something that would allow for very precise balancing and originally were going to use two electromagnets but that would require a power source everywhere we take it and we didn't want that inconvenience. The neodymium magnets are a good replacement.

I am really surprised just how out-of-round a lot of these tires are. The XO1 tires were really good but some of the others were, um, not so hot. I think I'll post another video of a few balanced tires just for S&Gs. As I'll warn before viewing... it may be about as interesting as watching paint dry!

-Shack

[Gripdog7205]

I have something very similar. It's not aluminum, but the magnetic principles, and mounting is the same.

[shack351]

I have something very similar. It's not aluminum, but the magnetic principles, and mounting is the same.

Hey Grip,

Good deal... how has it panned out for you? For me, it takes a little longer to balance each tire compared to the other method I was using but the results are well worth it. It is so sensitive to weight changes that you have to get really granular on your counterweight. I am adding 10th/g per spin once it gets close to balanced. Once I have the tire balanced, I remove all the little pieces, weigh them, and then construct a single piece to match their weight. If you really want it perfect, you just have to spend the time. Besides any performance gains, it definitely gives you a little extra piece of mind when you're ripping up the pavement!

-Shack

[Gripdog7205]

I agree it takes forever. Me end result was the smoothest runs I've had. Granted I'm not a 160 guy. Still rock solid over 100mph. I just cleaned the wheels and started rubbing tiny amounts of clay on the low spots. Add weight, balance, repeat

[broitsseth]

After seeing tire vibration issues at high speed, even after a basic balancing, a better solution was needed. I wanted a way to really dial-in the tires and my friend came up with a great way to do it. This is 100% his design and I think it is brilliant. I know that most people don't care about micro-balancing their tires but I thought I would share this piece of hardware.

Here is a short video of the device in use. I have put 15 or 20 tires in it so far and it is amazing to see the difference between the same type tires. One set of tires that I checked varied wildly from tire to tire in balancing and general "trueness". I will say that the XO1 tires looked pretty good. One tire in particular stood out as "off" but they were nice and round in general. I was thinking that the "thread" balancing technique was good but all the tires that I thought were balanced, the new device revealed they were not.

-Shack

thats awsome!
id build one but im no speed freak like some of the other people here

[Miltdoggie]

This is awesome!! Now that I can see the video, lol.

Good thing about foams, no need to balance tires. How much do one of these run for?

[shack351]

This is awesome!! Now that I can see the video, lol.

Good thing about foams, no need to balance tires. How much do one of these run for?

Hey Milt,

Well, since it's a one-off, custom piece, I guess it's priceless! LOL

As for foams, the BSRs that I did needed balancing, too. I checked a full set and all of them needed a little tweaking. I don't think there is a tire made that is perfect. The GRP Velocity tires I did were pretty good but they needed some balancing as well. So far the Traxxas XO1 set that I balanced is still the best. They spun nice and true and needed very little weight to balance them.

-Shack

[shack351]

thats awsome!
id build one but im no speed freak like some of the other people here

Thanks brother! It is definitely not something that most people need. I like to dial-in every aspect of the rig so having this device was a must for my obsession!

-Shack

[shack351]

I agree it takes forever. Me end result was the smoothest runs I've had. Granted I'm not a 160 guy. Still rock solid over 100mph. I just cleaned the wheels and started rubbing tiny amounts of clay on the low spots. Add weight, balance, repeat

What's up Grip!

It is definitely a slow process of trial and error but I agree... the results are worth it! My method is basically the same as yours. Just keep going until you get it right! The spin-up attachment built on to the side of the balance is nice as well. It needs a little more work but will hopefully be ready in a few days. Then you can spin the tire up to different rpms and check for issues.

Since my area totally sucks for long, straight and flat roads, the chassis dyno is the next item on the to-do list. Another buddy who is a pilot said he knows of some private airstrips that are within an hour or two from where I live that might be a possibility but I need something else. I know everybody is tired of talk and wants to see action. Believe me, there is nothing I want more than to show the work that has gone into this project but I just can't risk flying into a pole, fire hydrant or whatever... at 150+. I have seen enough videos of these dudes having a little bad luck and hitting something solid at high speed. The rig basically explodes and you're left with a bunch of pieces. I REALLY want to avoid that if possible! I have driven it over 100 but I already told myself that I will not post a video of any speed under 150, unless it's a nasty crash! The goal is still 200MPH!

-Shack

[Gripdog7205]

What's up Grip!

It is definitely a slow process of trial and error but I agree... the results are worth it! My method is basically the same as yours. Just keep going until you get it right! The spin-up attachment built on to the side of the balance is nice as well. It needs a little more work but will hopefully be ready in a few days. Then you can spin the tire up to different rpms and check for issues.

Since my area totally sucks for long, straight and flat roads, the chassis dyno is the next item on the to-do list. Another buddy who is a pilot said he knows of some private airstrips that are within an hour or two from where I live that might be a possibility but I need something else. I know everybody is tired of talk and wants to see action. Believe me, there is nothing I want more than to show the work that has gone into this project but I just can't risk flying into a pole, fire hydrant or whatever... at 150+. I have seen enough videos of these dudes having a little bad luck and hitting something solid at high speed. The rig basically explodes and you're left with a bunch of pieces. I REALLY want to avoid that if possible! I have driven it over 100 but I already told myself that I will not post a video of any speed under 150, unless it's a nasty crash! The goal is still 200MPH!

-Shack

You seem bright enough to do it. I really think tires and aerodynamics will be be your greatest obstacles. You've got the engineering part licked. Good luck

[shack351]

You seem bright enough to do it. I really think tires and aerodynamics will be be your greatest obstacles. You've got the engineering part licked. Good luck

Thanks for the vote of confidence brother... I appreciate it. And we're on the same page with tires and aero. I have looked for someone who has a bonafide, certified 150+mph tire and they are slightly hard to come by. I think foam is the answer but since all foams are not created equal, finding the right one is key.

As for aerodynamics, I have 4 different 2mm Delta bodies so hopefully at least one will be up to the task at hand. If I can just keep the rig in one piece long enough to test some of them, I might be OK. The dyno will be a good tool but there's nothing like the real thing!

-Shack

[Gripdog7205]

Thanks for the vote of confidence brother... I appreciate it. And we're on the same page with tires and aero. I have looked for someone who has a bonafide, certified 150+mph tire and they are slightly hard to come by. I think foam is the answer but since all foams are not created equal, finding the right one is key.

As for aerodynamics, I have 4 different 2mm Delta bodies so hopefully at least one will be up to the task at hand. If I can just keep the rig in one piece long enough to test some of them, I might be OK. The dyno will be a good tool but there's nothing like the real thing!

-Shack

Google Johns BSR foams. My purples are supposedly good for 160+. Or look at Banana Skinz racing foams

[shack351]

Google Johns BSR foams. My purples are supposedly good for 160+. Or look at Banana Skinz racing foams

I haven't seen Banana Skinz (will check them out) but I sent Johns BSR about 4 or 5 emails from multiple accounts over a 3 week period and never even got a reply. Way to run a business! Anyway, I am waiting on a decision from a company called Schumacher out of England. He might be able to do a custom solution on the wheels of my choice. We'll see how that goes.

Just curious... what is the OD for your BSRs? I want something at least 4". Thanks.

-Shack

[Gripdog7205]

Mine are on Prisim wheels so they're over 4. I'll measure when I get home. I called BSR and got John right away. Maybe that bridge has been burnt. The Banana Skinz is a guy. You send him the wheels you want foams on and he makes them. Apparently he's awesome. Look at my posts about foams. GeneralPede sent me a link to him. 48 bucks a set, no wheels.