Re-inventing the 1/8

[Greengaunja]

I'm not sure if anyone has actually done this but I can't seen to find anything. So I wanted to float an idea I plan to implement for the upcoming speed run season.
I've been doing research and looking at ways to crack the 150mph club. Short of just getting the XLX2 or squeezing in a Max5, what could be done? So I hit up Google and happened to come across Scorcheds new Trident shafts.

A good point is made in the description about how the stock shaft angles are not very efficient and how the Trident shafts compensate for it. I mean, it DOES make sense. But what if you eliminate the angles? Wouldn't that be more efficient than even the Trident?
I had plans for awhile to do a custom CF chassis. The main hold up has always been I don't want to fabricate one. I know nothing about doing CF from scratch or molds etc..but I know how to measure, even precision measurements with my trusty ancient Mitutoyo caliper and I know how to use quality tools and I know what cuts what. That's my area of expertise and that means cutting pre-made CF plates. But plates are flat and the bulkheads need front bulkhead kick. And I hate the idea of wedges for that purpose. Then I saw something amazing!

See it? You can buy the front bracket alone! So now we all know my next project. Here's where I'm going to change things you...
Every time I looked at my Senton, I always wondered why ARRMA would sacrifice drive train efficiency by offsetting the center differential just to center two tower braces? Granted maybe it's added strength that way but I highly doubt any strength is lost by lining the center differential up with the towers and offsetting the braces. Especially when those braces are reinforced with a T2T brace.
So the million dollar question fit you all is, would the drive train benefit with center shafts dead straight and with very little slop? Or did I throw something else off here? I'm not worried about the width of the chassis as I know I have room to widen it if need be. And both stock 1/8 Senton and the GT bodies wouldn't be effected.

 

[StephenSchandelmayer]

Seems we are in the same wavelength here!

https://www.arrmaforum.com/threads/new-project-custom-chassis-king-carbon.60045/page-2#post-894620

I just fitted mine tonight. Granted I wasn't super precise but this isn't being built for mega speed anyways

 

[Surchaufeur]

Very interesting. But i could see the screws backing out as an issue if implemented on new rc cars

 

[Greengaunja]

Very interesting. But i could see the screws backing out as an issue if implemented on new rc cars

I'm not sure I follow what you mean. If you mean from the underside of the chassis, they shouldn't. The holes would be countersunk and locktite used. The towers, motor mount, braces, and battery mounts would all be aluminum. The chassis itself isn't threaded. If I'm wrong about what you mean, don't hold back. This was why I posted up. I know there has to be a thing or two that I'm overlooking here.

 

[Dan B.]

The Scorched full length chassis centers the motor mount to get rid of the high misalignment center shafts of the Arrmas. That’s why they originally made the front Trident shaft. Probably wouldn’t be necessary with centered middle diff and shafts. I’m with you, I don’t see a downside.

 

[Greengaunja]

Ok, moving along.
I now have a template. Took some good advice from @StephenSchandelmayer and used my old original chassis that was funnily bent straight after a head to head meeting with a Kraton during my first(attempted) speed run. One thing I knew for sure was I needed a bigger chassis for all the crap on it now

You can see how the CF ESC mount and CF battery mount protrudes past the chassis itself.

With only the plastic side skirt protecting the ESC and a CF rail protecting the battery, it's a miracle I never had a side impact destroy them. So here's what I have in mind:*the black marked lines trace out the original chassis and the filler is cardboard and tape. Next I drilled some new center tower holes to push it over. Already one problem.

I managed to just clear the input cup. In fact if my math is right, and I suck at math, I may need to grind 1/8-3/16 off of the cup. No biggie except for the fact that I want to put an XLX2 in this and no sure if the motors are bigger or if there is anything to gain pairing another 4985 1650kv with it. Thats a problem for another day though. Worst case scenario, I fallback to the original mounting holes and order the Trident shafts to try .

Right now I'm working on something to cut my CF plate with. Had this idea to build my own mini CNC. And sometimes my ideas have drawbacks. No issues with a cutter, was given a rotozip last year that I never had a use for and there are hundreds of plans/kits to incorporate rotozips into a CNC online. The drawback? Didn't realize I'd need to program sh1t. But alls good. What I lack in computery skills I make up for in hand/eye coordination. Working on dust collecting router table. Scorched order lands on Monday and CF plate will be in on Wednesday. So by next weekend I will have an update on either a great DIY chassis or a colossal waste of money. Stay tuned!

 

[StephenSchandelmayer]

Ok, moving along.
I now have a template. Took some good advice from @StephenSchandelmayer and used my old original chassis that was funnily bent straight after a head to head meeting with a Kraton during my first(attempted) speed run. One thing I knew for sure was I needed a bigger chassis for all the crap on it nowView attachment 280869You can see how the CF ESC mount and CF battery mount protrudes past the chassis itself.View attachment 280870With only the plastic side skirt protecting the ESC and a CF rail protecting the battery, it's a miracle I never had a side impact destroy them. So here's what I have in mind:*the black marked lines trace out the original chassis and the filler is cardboard and tape. Next I drilled some new center tower holes to push it over. Already one problem.View attachment 280878

View attachment 280877I managed to just clear the input cup. In fact if my math is right, and I suck at math, I may need to grind 1/8-3/16 off of the cup. No biggie except for the fact that I want to put an XLX2 in this and no sure if the motors are bigger or if there is anything to gain pairing another 4985 1650kv with it. Thats a problem for another day though. Worst case scenario, I fallback to the original mounting holes and order the Trident shafts to try .

Right now I'm working on something to cut my CF plate with. Had this idea to build my own mini CNC. And sometimes my ideas have drawbacks. No issues with a cutter, was given a rotozip last year that I never had a use for and there are hundreds of plans/kits to incorporate rotozips into a CNC online. The drawback? Didn't realize I'd need to program sh1t. But alls good. What I lack in computery skills I make up for in hand/eye coordination. Working on dust collecting router table. Scorched order lands on Monday and CF plate will be in on Wednesday. So by next weekend I will have an update on either a great DIY chassis or a colossal waste of money. Stay tuned!

View attachment 280867

View attachment 280868

I have faith!!! I think you are going to nail it dude I think this will be sick. I can't wait to see what you end up with. I did some progress tonight as well.

 

[Diem Turner]

The Scorched full length chassis centers the motor mount to get rid of the high misalignment center shafts of the Arrmas. That’s why they originally made the front Trident shaft. Probably wouldn’t be necessary with centered middle diff and shafts. I’m with you, I don’t see a downside.

Not exactly. The Trident shaft was created to address the the downward angle of the front diff input that we get from the kick-up at the front up to generate caster in the front suspension. That's why there's only a front Trident shaft. If it had been made to address the misaligned motor/diff mount, you would expect to see a rear Trident shaft as well but, we don't. If you take a look at the product description they go on to say as much:

"After 12 months of design and development we have solved the problem of the Arrma front centre shaft.

The kick up in the arrma chassis created 2 problems for people running very high speed Arrmas.
The first is uneven drive speed to the front wheels. Dog bones act in a similar way to universal joints, which introduce accelerations to the shaft speed when there is an angle. This can’t be good on many levels. Look up universal joint shaft velocity to fully appreciate this issue.
The second, big problem is friction. Because of the angle, the dog bone pin slides backwards and forwards in the cup, under load, at something like 500 cycles per second (!)."

 

[Greengaunja]

Not exactly. The Trident shaft was created to address the the downward angle of the front diff input that we get from the kick-up at the front up to generate caster in the front suspension. That's why there's only a front Trident shaft. If it had been made to address the misaligned motor/diff mount, you would expect to see a rear Trident shaft as well but, we don't. If you take a look at the product description they go on to say as much:

"After 12 months of design and development we have solved the problem of the Arrma front centre shaft.

The kick up in the arrma chassis created 2 problems for people running very high speed Arrmas.
The first is uneven drive speed to the front wheels. Dog bones act in a similar way to universal joints, which introduce accelerations to the shaft speed when there is an angle. This can’t be good on many levels. Look up universal joint shaft velocity to fully appreciate this issue.
The second, big problem is friction. Because of the angle, the dog bone pin slides backwards and forwards in the cup, under load, at something like 500 cycles per second (!)."

Already on it. My old build took 1/8 of that out with a simple mod that raised the center tower.

Almost everyone with the Max 6 combo has done this or should do it. The motor should never touch the chassis or bad things happen with the slightest impact.. I'm working on a base plate for the rear tower. I wont get this perfect, but I can come close. The automotive industry has already proved the concept I'm shooting for. The straighter any shaft is, the more efficient it is. Even when u joints become necessary, effort is put into making them as straight as possible with the u joint taking care of the margin of error.
Another thought here. I've debated the effectiveness of a proper u joint(CVD) vs the cup/dogbone acting as a u joint. Is there anything to gain from ditching the input cup with a slotted pin going into the differential attached to center shafts just like in crawlers? If you saw the MIP adjustable length shafts I have in my SCX10.iii and how beefy they are, you would really see why I'm thinking this. Those shafts would need a sledge hammer to break them.

The guy who designed these 316 Surgical Steel shafts explained to me that the reason he shaped the ends of these dogbones the way he did was to slightly improve efficiencyby having a firmer fit in the cup and more clearance on the ends to cut back on friction. He was actually the first to point out the fault in the drivetrain to me and how exactly it's problematic.

 

[Koma7]

 

[Dan B.]

Not exactly. The Trident shaft was created to address the the downward angle of the front diff input that we get from the kick-up at the front up to generate caster in the front suspension. That's why there's only a front Trident shaft. If it had been made to address the misaligned motor/diff mount, you would expect to see a rear Trident shaft as well but, we don't. If you take a look at the product description they go on to say as much:

"After 12 months of design and development we have solved the problem of the Arrma front centre shaft.

The kick up in the arrma chassis created 2 problems for people running very high speed Arrmas.
The first is uneven drive speed to the front wheels. Dog bones act in a similar way to universal joints, which introduce accelerations to the shaft speed when there is an angle. This can’t be good on many levels. Look up universal joint shaft velocity to fully appreciate this issue.
The second, big problem is friction. Because of the angle, the dog bone pin slides backwards and forwards in the cup, under load, at something like 500 cycles per second (!)."

I stand corrected, you’re absolutely right.

 

[Greengaunja]

I stand corrected, you’re absolutely right. I’ve thought of lowering my mount to help that situation but it would limit pinion spur combos for sure.

I may get a PPS mount. This build won't happen fast and I had to order a ton of pricey parts, including HR bulkheads. Take a look at the pic I shared. The center is raised 1/8 but the shaft isn't at much of a downward angle as it was. The kick now seems to be the center. I'm not considering lowering it for the reason you pointed out. But I'm suggesting tweaking it like adding 3 1/16 shims to back 3 bolts or removing 2 from the front bolts of the diff carrier? Granted, I will need to play around with that and of course, it throws the rear off. Hence a need to make a base ring to evenly raise the rear bulkhead. Which brings me to another question for you. I always assumed stock, HR, PPS mounts were the same, spec-wise, with the real difference with PPS is they made their tweaks in the slider, allowing the motor to move further out for larger pinions. Are you saying it actually positions the motor higher too? Because that would just be another selling point to me.

Ultimately, the main issue is ARRMA simplified the parts for us. Would have been better to have specific front and rear bulkheads, with the diff assembly angled.

 

[Dan B.]

I may get a PPS mount. This build won't happen fast and I had to order a ton of pricey parts, including HR bulkheads. Take a look at the pic I shared. The center is raised 1/8 but the shaft isn't at much of a downward angle as it was. The kick now seems to be the center. I'm not considering lowering it for the reason you pointed out. But I'm suggesting tweaking it like adding 3 1/16 shims to back 3 bolts or removing 2 from the front bolts of the diff carrier? Granted, I will need to play around with that and of course, it throws the rear off. Hence a need to make a base ring to evenly raise the rear bulkhead. Which brings me to another question for you. I always assumed stock, HR, PPS mounts were the same, spec-wise, with the real difference with PPS is they made their tweaks in the slider, allowing the motor to move further out for larger pinions. Are you saying it actually positions the motor higher too? Because that would just be another selling point to me.

Ultimately, the main issue is ARRMA simplified the parts for us. Would have been better to have specific front and rear bulkheads, with the diff assembly angled.

From what @Diem Turner told me I would go with the Scorched motor mount because it’s a concentric circle with inserts that allow you to actually put the height where you want it and still set the mesh. At least I think that’s what he said. He said it’s just a brilliantly engineered product. I would have made that choice, but I’d already purchased the PPS mount (and yeah, it also positions the motor higher, he designed it to get the fat-can motors in) so that’s what I’m using.
I‘m working through the same issues you are right now with my build.
I now fully understand what he said about the front chassis kickup that provides a downward angle to the front drive cup. I’d never really digested that, having been fixated on the shafts being so off center. At the least if you center the mount you’re doing away with that stupid offset angle, and that has to help a lot.
I’m enjoying your thread, man!

 

[@9G]

Another mount you can check out is the EM Performance mount. It raises the motor higher also much like the PPS. It uses 4 screws on the sliding plate instead of just 2 like most other mounts. I was able to put a TP 5450 in a SWB chassis with it and there's plenty of clearance from the bottom of the motor to the chassis.
Here's the link: https://emperformanceproducts.com/p...-diameter-and-reinforced-hardened-drive-cups/
I had the Scorched Roto Mount also and I liked the rotating feature but the center piece got damaged quickly after a few pinion changes. The center part that actually does the rotating to make mesh isn't strong aluminum like the rest of the mount. There's a small hole to put a driver through to get to the pinion grub screw but it gets worn pretty fast. Shame too cause the mesh from that mount is probably the best I've seen in my short RC experience. I actually damaged 2 of those pieces. There was issue with the mounting screws too when I bought mines and Mr. David sent a personal email to let me know about the error. Scorched has FANTASTIC customer service.

 

[RedOctobyr]

Cool discussion! This is probably old news. But just please be careful when cutting carbon fiber. You don't want to be breathing that dust, or getting the CF shards/splinters stuck into your fingers. If it were me, even with dust collection, I'd be wearing an N95 mask, and maybe nitrile gloves, or similar. Safety glasses are a given, of course.

Maybe even do the cutting outside, if possible?

 

[Dan B.]

Cool discussion! This is probably old news. But just please be careful when cutting carbon fiber. You don't want to be breathing that dust, or getting the CF shards/splinters stuck into your fingers. If it were me, even with dust collection, I'd be wearing an N95 mask, and maybe nitrile gloves, or similar. Safety glasses are a given, of course.

Maybe even do the cutting outside, if possible?

Great advice, do it. Times in the past I haven’t. Fingers looked like I encountered a 1:10 scale porcupine and my lungs said, “dude, really? WTF?”

 

[Greengaunja]

Cool discussion! This is probably old news. But just please be careful when cutting carbon fiber. You don't want to be breathing that dust, or getting the CF shards/splinters stuck into your fingers. If it were me, even with dust collection, I'd be wearing an N95 mask, and maybe nitrile gloves, or similar. Safety glasses are a given, of course.

Maybe even do the cutting outside, if possible?

Sound advice. I've been working with CF plates to make parts for awhile now. The mask and dust collection is common sense but just the same, it doesn't hurt to remind people. The two things I learned the hard way are NEVER do CF cutting or sanding in a t shirt and wear thick heavy gloves because that sh1t splinters in razor sharp shards! Even tweezers have a rough go pulling them out of your hands. Oh and a third thing: wet sand as much as you can under running water. Not only gives a better finish, it controls dust alot better

 

[RedOctobyr]

Yikes. If tweezers can't manage it, ouch! I have worn heavier rubber gloves (think like dishwashing gloves) for some things. Or snug-fitting leather gloves might work, for better puncture-resistance.

 

[Greengaunja]

Yikes. If tweezers can't manage it, ouch! I have worn heavier rubber gloves (think like dishwashing gloves) for some things. Or snug-fitting leather gloves might work, for better puncture-resistance.

Yeah thick leather work gloves are what I use now. At first I used to use those thin vinyl/latex gloves and they were useless. The thicker rubber dishwasher ones MIGHT be OK, but the shards and slivers are so razor sharp I never felt them entering. I would only know I had them if something brushed the area it and I'd feel it catching and being moved. Irritating as hell and frustrating trying to get them out. And the dust? Ever handle fiberglass insulation? Twice as itchy and the "cure" is the same for both, very cold water(closes your pores) flush. Use warm water and just like insulation, it gets worse!

 

[Dan B.]

Oh and a third thing: wet sand as much as you can under running water. Not only gives a better finish, it controls dust alot better

That makes sense, I’ll definitely try it. I’ve only recently started working with CF. Discovered what you’ve said above pretty quickly, stuff is nasty to human flesh!