Chris's "Cow Ant" XR Crawler Build

[coliver14]

Got the assembly finished in SketchUp. Here are some progress pics...









And the finished look with grey aluminum members (I'm going to try and have them bead blasted for a flat, metal finish) and the orange Axial posts.







Of course I'm biased, but I think the chassis turned out looking pretty good. What do ya think?

Chris

[brazwewn]

Looks good. I am thinking you cold probably drop several of those cross braces and still maintain the rigidity needed. It will save you a few ounces for sure.

Wes

[coliver14]

Originally Posted by brazwewn

Looks good. I am thinking you cold probably drop several of those cross braces and still maintain the rigidity needed. It will save you a few ounces for sure.

Wes

Meh, total weight for all the cross members and spacers is less than an ounce.


Here's the aluminum strips I plan on using for the chassis members.


This particular aluminum came out to 1.572oz/in^3. The total volume of aluminum that makes up the chassis (taken from SketchUp) is 2.29in^3. This will put the chassis weight at around 3.6oz without the cross members, and 4.5oz with the cross members.

Chris

[oo C64 oo]

Can i ask a noobish question?? For me a crawler is so god damn powerful why are weight reductions necessary? Is this a comp thing? Also I notice lots of people adding heaps of weight to their wheels, which seems to circumvent any gains made on weight reductions in the first place... Or is this a centre of gravity issue I am missing? Thx guys!

[BliB]

Originally Posted by oo C64 oo

Can i ask a noobish question?? For me a crawler is so god damn powerful why are weight reductions necessary? Is this a comp thing? Also I notice lots of people adding heaps of weight to their wheels, which seems to circumvent any gains made on weight reductions in the first place... Or is this a centre of gravity issue I am missing? Thx guys!

Yep, lowers CoG and making it heavier in the front

[Jakerz]

I can see where the lightweight chassis' are a good thing to lower the CG, but people go WAY overboard to me with the aluminum hardware and all on the axles. Why put screws in your front axles that are 25% the strength but lighter and then add knuckle weights? lol. The drilled gears are lighter and they also reduce rotating mass but I still cant see that making a huge difference with a 30:1 gear ratio either, idk maybe I think differently lol.

[brazwewn]

Originally Posted by Jakerz

I can see where the lightweight chassis' are a good thing to lower the CG, but people go WAY overboard to me with the aluminum hardware and all on the axles. Why put screws in your front axles that are 25% the strength but lighter and then add knuckle weights? lol. The drilled gears are lighter and they also reduce rotating mass but I still cant see that making a huge difference with a 30:1 gear ratio either, idk maybe I think differently lol.

Try driving a lightweight rig and you will understand.

Wes

[Jakerz]

Originally Posted by brazwewn

Try driving a lightweight rig and you will understand.

Wes

I understand the lightweight thing but how is 1 oz of screws and 2 oz of knuckle weight different than .5 oz or screws and 2.5 oz of knuckle weight?

Jake

[coliver14]

In light of the 2013 rules change, I decided to lower the chassis height and overall ride height by 1/4" to give the CowAnt a more streamlined look.

The image below shows the difference between the original and the new design.


It's not a huge change but it is noticeable. I also added some upper link mount adjustment holes to allow some tweaking. Here's what the new design looks like in sketchup...








As far as construction goes, I started making the straight members first to get the hang of working with the aluminum. Here's kind of the sequence I've been going with...

First make a mark slightly wider than the 3/8" target member width.


Then, using a dremel tool and cutoff wheel, start making a cut parallel to the mark.


3-4 cutting wheels later...


Then, using a table-top belt sander, I grind the piece down to 3/8" wide.



Next, I make marks for the length and hole locations for the member.


All holes are started and centered with a 1/16" bit, then bored with a 3/32" bit to check the alignment again, and finally with a 1/8" bit to fit 3mm hardware.


And voila!


To make the bends, I simply use a vice and good 'ol elbow grease.


I use a "rotating square" (not sure if that's the correct term) to verify the bend angles.


Also, a level helps with verifying angles.


Anyways, it's a tedious process getting the pieces just right but pretty cool seeing it all come together.


I should have the remaining pieces finishing by this weekend and hopefully I'll be able to get them sand blasted for a cool finish.

Stay tuned.

-Chris

[redrokin00XJ]

Originally Posted by Jakerz

I understand the lightweight thing but how is 1 oz of screws and 2 oz of knuckle weight different than .5 oz or screws and 2.5 oz of knuckle weight?

Jake

When you start comparing the weight differences in OZ then it wouldn't make a big change.... However.... When "they" refer to a lightweight rig it usually starts out at around 6lb rig goin down to a sub to mid 4lb rig. That is where you see the difference.

[redrokin00XJ]

Originally Posted by coliver14

In light of the 2013 rules change, I decided to lower the chassis height and overall ride height by 1/4" to give the CowAnt a more streamlined look.


It's not a huge change but it is noticeable. I also added some upper link mount adjustment holes to allow some tweaking. Here's what the new design looks like in sketchup...

That thing has gotta be the UGLIEST thing I've ever seen... On that note, it's all about what works good V.S what looks good.

BUT WHATEV!

[pajey]

This thing reminds me of the mecano cars.... I'm not sure whether all those cross braces are needed there seems to be quite a lot.

[ittybitty]

Originally Posted by Jakerz

I understand the lightweight thing but how is 1 oz of screws and 2 oz of knuckle weight different than .5 oz or screws and 2.5 oz of knuckle weight?

Jake

It's about getting the weight where you want it...as far out on the axles as you can move it and also below axle center line...and some of it ahead of the front axle center line. This also helps to accomplish the desired weight bias front to rear and side to side.

[ManxCrawler]

Originally Posted by coliver14

I bet your ears were singing after that

...I call it an adjustable protractor

[coliver14]

Originally Posted by redrokin00XJ

That thing has gotta be the UGLIEST thing I've ever seen... On that note, it's all about what works good V.S what looks good.

BUT WHATEV!

Thanks for the post! I could say the same thing about your switch chassis...but then I'd be offending 80% of this forum's users, so I'll refrain from doing so.

Originally Posted by pajey

This thing reminds me of the mecano cars.... I'm not sure whether all those cross braces are needed there seems to be quite a lot.

There are alot of cross braces, however the weight savings from removing a few of them is very minimal and, in my opinion, not worth it considering the loss in rigidity by doing so.

Originally Posted by ManxCrawler

I bet your ears were singing after that

They were (and probably still are)! I started using the reinforced cutting wheels instead of the brittle (ceramic/composite?) ones and they have greatly cut down on the sound.

Originally Posted by ManxCrawler

...I call it an adjustable protractor

Makes sense...I'll go with that.


A little more progress on the chassis pieces:


There are 4 more pieces I need to make in order to start assembling it.

In other news, I pulled the trigger on the tires/wheels and decided to go good 'ol white dot Rovers mounted on Vanquish SLW v3's, (orange rings on black, of course). I ended up going with the 0.7" width option.



Also, I ordered a Rowdy Racing front-axle battery mount:


I tried to keep the front and rear widths about the same so I'm using .475" and .725" hubs, respectively.


I found the axles to be suprisingly heavy:



So far, it's around 4lbs, 3oz. That's without electronics, battery, chassis, shocks and links! I'm shooting for 5lbs or less, we'll see how this ends up.


Stay tuned

[coliver14]

Chassis is finally put together! I still got to round the edges, grit-blast the members and paint it black, but here it is...











The chassis w/cross members and hardware weighs in at 5oz.



-Chris

[xgerstandtx]

I like the time you have invested in your design. Try some Cheesehead screws in the lower 4 that would attach to the skid, that should reduce some headache later when dragging that between two tight rocks.

Keep up the work.

[Jakerz]

I like it! its funny how much the 1/4 on height does for it lol

Jake

[coliver14]

Originally Posted by xgerstandtx

I like the time you have invested in your design. Try some Cheesehead screws in the lower 4 that would attach to the skid, that should reduce some headache later when dragging that between two tight rocks.

Keep up the work.

Thanks! That is a good idea about the flathead screws on the bottom for clearance. I'll probably do that once I decide how I'm gonna attach body panels (and a skid plate) to the chassis.

Originally Posted by Jakerz

I like it! its funny how much the 1/4 on height does for it lol

Jake

Yea, that quarter inch really gives it a more streamline look.


As shown below, I went ahead and rounded all the edges of the chassis pieces.









I ordered some 3/16" titanium rod tonight so I can begin making links this weekend.

[coliver14]

A few updates...

First, I pulled the trigger on Tomy's carbon fiber rear axle brace. Nice little addition for a few bucks (or euros)...




Then, I started making titanium links using 3/16" diameter, 6Al-4V Ti rod stock:




Cut to length using the good 'ol dremel tool...




Then, using my friend Jakerz's lathe, I turned down the 3/8" ends down to ~0.162"





Using an 8-32 dye, I was able to put some threads on the link ends:





Two down, six to go...
Anyone who's made links like this knows it's a tedious process but tolerable if you're hanging out at the same time (especially with drinks)...

Anyways, I'll post more pics once I finish all the links (and hopefully sliders as well). Stay tuned