Custom built CRAWLER

[momin]

Hi,

After seeing mud4funs's thunderfoot i feel like a bit of a project. Making a crawler. Can someone give me some hints on what a crawler needs?

How the suspension system will work?

And some ideas on what car to start on?

I am on a low budget so please dont mention something like a TXT-1.

thanks

momin

[emaxxjeremy]

well a decent low cost crawler is a tlt.

you can buy one for around $100 and go from there. for around $200 and some creativity it can be an awesome crawler

[mud4fun]

Hi Momin, nice to hear you are thinking of bulding one yourself.

One of the main reasons I never sold thunderfoot despite numerous generous offers is the fact that it is 100 custom/scratch built. If you lack the skills and/or equipment to build a truck like this then don't buy one off somebody else because you won't have the skills/equipment to fix it when it breaks. I wouldn't recommend buying a homemade crawler off anybody. I certainly don't won't to sell my truck because I don't want somebody complaining a month down the line that the special one off shaft has broken and they need me to make a new one!! I don't have the time or inclination so best not to sell - less hassle. (This is talking from experience of previous such situations)

By designing and building your own truck you will also learn to understand how the thing works, how suspension geometry affects handling and performance etc, etc.

It is unlikely you will build a perfect crawler first time. Thunderfoot is on its 10th+ incarnation with numerous changes, some fundamental, being made to the original design to sort problems out. Getting the torque twist under control, proper weight distribution, optimum wheelbase etc all require trial and error but make the building process more fun and enjoyable (at least to me) and make you feel much more proud when you finally complete it.

While thunderfoot only cost £100 in parts you must not forget that it also took in excess of 40+ hours of my time so for me to put a price on it would be difficult. My daily rate for my job is £1200/day so work it out! my time is very precious which is why I can't spare the time to build these to sell on to others - I couldn't charge enough for it to be worth my while.

I know that you can certainly build an impressibe crawler for far less than £100, you don't need monster truck axles or transmissions. Ingenuity and lateral thinking work wonders!

I'll send you some pics in the next few days of my latest extreme crawler. It will cost less than £80 and beat just about any clod based crawler costing 10 times that much [][] and yes, it is thundershot based.

[momin]

Hi ian,

i really like you projects.

can you send me the pictures to my email addresse mmfk786@hotmail.com.

And what type of motors are you running 540/550?

thanks

[fatboyslim]

I'll agree with Ian on that, there's nothing more satisfying then finally seeing your creation came alive!!

My home built crawler cost me around the £100 mark(not including R/C gear and ESC)and £70 of that was on the Clodbuster donor vehicle(which came from Ian strangley enough!!)

All the other bits and pieces were made by myself(except the 4-links which came from Twinset) using aluminium plate and 'C' section which came from B&Q and Homebase and loads of bolts and fasteners from a local bolt stockists!!

Like Ian said if your not mechanically minded the it's not easy to do, but it is loads of fun if time consuming!!(I actually built mine at work!!)

[Martin71RS(2)]

quote:My daily rate for my job is £1200

id="quote">id="quote">

He Ian, where do I get a job like that????? []

My first modclod was pretty cheap too....I used alu from the DIY....

Only when I started making it nice, put in fast motors, steel pinions, bearings, good shocks and such it became expensive....but even Clod based it is possible to make one cheap(ish)

Good luck and have fun!!

[mud4fun]

Hi Momin, I got your email regarding the exact sizes of parts used on thunderfoot and I'll reply here because others have also asked the same question:

Sadly I designed it out of my head, I never had any design drawn up or anything written down. All the parts were cut to size as needed as I built the truck. Many of them changed size many times to overcome various issues. To work out the sizes of all the parts so you could build a replica would mean I'd have to strip the truck down and measure up each part which also includes the gearboxes as I made up custom shafts - I simply haven't got the time at the moment to do that.

However, I am going to fully document my next extreme crawler 'Terrafoot' with proper drawings of all parts so if you can wait a few weeks I'll have all the info you'd need.

---

I'd say the things you need to look for in a crawler (especially one for rock crawling) are as follows:

1) Lots of underbelly clearance (4" or more)

2) Lots of under diff/axle clearance (2" or more)

3) 13"+ wheelbase or longer

4) Low CoG (1 and 2 make it higher of course)

5) Motor with lots of torque

6) Very low gearing (min 50:1, thunderfoot runs 65:1, higher ratio=lower gearing)

The complication comes because you can't simply have a crawler with huge amounts of everything above. You will have to compromise and it is the amount of compromise on each item that makes everybodys trucks unique.

The longer the wheelbase, the better your truck will climb up and onto steep steps/rocks however you will then lose you approach and departure angles which will limit the size of rock you can clear.

Bigger tyres will give instant increases in clearances under the chassis but have the adverse affect of requiring more powerful motors and they result in reduced run time. Thunderfoot runs 2.2" tyres which are far smaller than Clod tyres but because of careful design the chassis still has as much clearance as Clod based machines.

Very low gearing will allow you to climb much more easily and also allow you to drive the vehicle with incredible amounts of precise control on tricky sections but it results in a very slow vehicle which means you can't drive it anywhere but on the sections. Some sections have time restrictions and if you are too slow you'll get penalty points!

Having a low CoG is great but that needs to be balanced with good ground clearance. No point if having a CoG really low down if your truck can't make it over even a small stone!

Check out the search facility on this site (on the menu on home page) it allows you to search for crawlers, home made parts etc. You should find lots of other crawlers that TC members have built themselves which will give you an idea of what to design/build.

Also check out www.rccrawler.com which is an American site where the hobby of crawling is much more advanced. There are some awesome rigs on that site!!

I hope this helps.