Mr. Crawley is my best try until now to design a pure RC Crawler Chassis, following what seems the market standards in terms of measurements, elements disposition and functionality.

You can see it in 3D here

It is designed to fit where an axial SCX10 chassis would fit, as it tries to respect some important measurements, like the axles width, the frame shape, length and width, the shock or body holders positions or the electronics disposition over the frame.

As I'm not an expert about RC crawling, this time I counted with who is an expert to my eyes to take many of the design decisions, the user ConorHyena who already bought and tested my previous "crawler" design, the MTC Chassis Rigid Axles and who has been a great help to achieve what I think is a great result!

With a little extra feedback from Reddit r/rccars and r/crawling I included a version of the axles with the input tilted a few degrees up to improve clearance. Anyway, for those "mechanically correct" lovers, I also include the axle version with the input aligned with the gearbox outputs, so the universal joint shafts doesn't suffer extra wearing.

As the market standard, I designed this chassis to have a 313mm wheelbase. You can achieve shorter wheelbases. For that I created 2 different central side bars which will allow you to use the Mid-Long one (for 155 or 145 mm front partial wheelbase) or the Short-Mid one (for 145 or 135 mm front partial wheelbase). If you want even shorter front partial wheelbase you will need to use shorter front links for the 125mm one. For the rear partial wheelbase, I created 3 different length rear side bars, the standard ones for 155 rear partial wheelbase, and 10mm and 20mm shorter ones. 

Of course, shortening the frame isn't all... you will need to use the different upper and lower links sets to have the partial wheelbases you are looking for. With these possibilities, you should be able to build any wheelbase from 253 to 313 (when fully horizontal), but I haven't tested them all.

The key of this design, I think the same than in my previous ones, is that it uses important sourced parts like F/R differentials, pinions and half shafts, so it is quite more reliable than a fully 3D printed chassis design. Those parts are not very picky, so you should be able to find them easily for very little money.

For this basic version, you will also need a SCX10 style sourced gearbox.

It allows you to mount the servo over the axle or over the frame, is up to you if you prefer better looking or better handling... You can also add steering to the rear axle if you want. It is planned to add 3 link + panhard links for the front steering axle to avoid bump steer.

For those looking for the best crawling performance the rear tray position for a big the battery will not be a great idea. It is planned to add soon as an option some side "Sliders" which would allow to attach there smaller batteries, something like 3S 1300mah, the same than a front battery tray which could also have place for the ESC and receiver. In addition, there will be probably an alternative rear tray, in a lower and transversal position also for small batteries.

Remember you can also print it if you want, with the same gears pitch and teeth, getting it here. If you are also interested in the Portal Axles for Mr. Crawley, then I would recommend you to get the "MyRCCar MrCrawley Complete RC Crawler Chassis"

Beyond all those possibilities, I also designed the Portal Axles for you to build a higher car if you want! They are a little more complicated than standard ones, but the 13mm extra clearance with floor can be the difference for overcoming some obstacles...

All the design is using M3 screws... different lengths of course. You will find attached a list of the needed screws with a short description of where to use them

The bearings are the most standardised sizes, you will probably already know them... those are 5x10x4 and 10x15x4 bearings... 8 of each kind to build the axles.

I'm using HSP 02024 differentials, or "cloned ones", the same than 02030 pinions and 18027 universal shafts for the central transmission. From the differentials to the wheels I'm using HSP 102015 universal joint half shafts, but you should be able to use also HSP 122015 CVDs. You should be able to get all these transmission parts for less than 25€ with 10-day delivery from Aliexpress... Maybe cheaper if you enjoy deeply searching the whole Aliexpress! If you want also the SCX10 gearbox, you will need another 20€ for it. You will be able to find many or all of these parts also in Amazon, but the price will be higher of course.

I'm using 90mm shocks for the build, 1/10 standard sized ones or big bore ones should work perfectly. 
 The same way, I'm using typical 98mm wheels, with standard rim size... they should be easy to find too.

Special parts for Gearbox and Portal Axles:

Beyond that, if you want to print and build your own gearbox, you will also need a 47mm length 5mm diameter metal shaft and a rotary tool to "metal-smith" it and use it as the output shaft from the gearbox. You will need to make a plain surface in the extremes of the shaft so you can attach the Universal Joint transmissions, the same than you do in the 02030 pinions.

For the portal axles you will also need four M5x10 grub screws and four M4x16 screws for attaching the wheels to the axles.

As for most of 1/10 RCs, you will need a motor and ESC, a servo, a radio and receiver, a battery and its charger. I'm using a brushless sensored motor + ESC, but I think the brushed motors, which I don't know very well, will do a great work for a crawler, as the low speed control can be better than any sensor-less brushless motor, but probably also better than the sensored ones.

The space for the battery in the rear tray is 150x50mm, which should allow you to choose a quite big battery if that is what you want. Probably any 2S LiPo battery with some > 25C

The 3650 motor is the standard, but you should be able to go with a longer one, maybe 3660 or 3670 if you don't mind moving the front upper link holders to another spot.

For the servo, if you are not very exquisite with response time or strength, maybe something around 10€ should do the work, of course standard sized 1/10 servos.

With your extra feedback after building and testing this design, I want to create Upgraded Parts which will be free if they solve verified problems. The same way I will be willing to create new parts for it which will improve or allow new features so all ideas will be welcomed.