Budget DIY Crawler - Potential Gearboxes and Axles?

[30YrsL8r]

After the suggestion that there might be a meet at Delamere Forest, I was wondering if I could do something similar after reading this blog post again:

http://mud4fun.wordpress.com/rc-rock-crawler/

I don't have the spares that this builder had and so:

1) Are Thundershot front (x2) and rear (x1) gearboxes the best, cheap option?

2) If so, does anyone have some in their bits bin that they'd be willing to part with?

3) If not, what else would fit the bill? Ideally I'd like a good reduction in gearing just using the 'boxes themselves.

[Percymon]

Thunder shot gearboxes are very reliable, but you could actually make a fairly reasonable forest track crawler with a TL-01 chassis with locked diffs and some cheap crawler wheels. Add a 35/55t motor and you are away

Even the DF01 chassis was used for a few off road variants by adding bigger wheels and gearing down.

[skip665]

I am looking to sell my Thunder Dragon (same as Thundershot) with all the spares I have with it. The buggy has been with me since the early nineties but the body is trashed and I need to either do something with it or sell it. I am pretty sure I have most of another one as spares too. Its fully ball raced too.

I don't want a lot for it - let me know if you are interested and I can get you some pics...

[mr crispy]

That's a very interesting build blog, got me thinking now. Of course if you follow his method and use to front axles you could easily have 4ws!

[30YrsL8r]

Of course if you follow his method and use to front axles you could easily have 4ws!

I'm wondering about two rear axles for MoA and use the front hubs on them to get 4WS.

I wont get the gearing down from using the output of the rear gearbox on the input to the front gearboxes, but I could use high turn motors instead, I suppose.

[mud4fun]

30YrsL8r,

I thought I should point out that while the thundershot gearboxes have proved OK in my truck and I've certainly not had any reliability issues with them, the only reason I used them was because I had literally stacks of thundershot parts in stock from my buggy racing days. I had also bought hundreds more thundershot parts to restore my fleet of buggies. So with boxes full of them I thought I'd put them to good use. I might well have used parts from another buggy or truck had I had those in stock instead. The idea of 'thunderfoot' was to build a crawler as cheaply as possible with as few new parts required as possible.

These days if I was building another truck from scratch I may well choose different components. That said however the thundershot based truck has proved very reliable and the only issues I've suffered have been with the propshafts which occasionally sheer at the plastic yokes from the torque generated by the cordless drill motr/reduction gearbox and overall low gearing of the transmission. It has also suffered from the dogbones pulling out of the drive cups when applying full power while under full steering lock. This was however found to be because I'd forgotten to fit the rubber O rings in the drive cups and me locking the wishbones in their lowest position to give good under diff clearance. I fitted an O ring into the cups at each end of the dogbones and since then the problem has not re-occurred.

I'm hoping to upgrade my blog to allow videos in the next month or so and I will upload some new footage of thunderfoot in action. It is by no means as capable as the dedicated crawlers that you can buy these days but in its day and for the £100 it cost to build it was pretty good.

Regards,

Ian

[bromvw]

Can I add my two penny's worth chaps ? Surely a crawler needs live axels and 4 links . Given that the likes of T Rex 60's are easily and fairly cheaply available a scratch built crawler is now well within reach . Using second hand parts from perhaps RCrecycler I recon you could still build a capable crawler for around £100 plus the electronics .

[TWINSET]

Can I add my two penny's worth chaps ? Surely a crawler needs live axels and 4 links

Check the link in post 1 - the axles are live and 4 linked

Wild Dagger gearboxes are another option and, as the motor's attached to the gearbox, the drive is a bit easier to arrange

Another 'cheap' option is http://www.modelsport.co.uk/?product_id=38123

Uses a lot of Axial pattern parts, so spares are pretty easy to come by

[bromvw]

Ok thanks Andy - I see what you mean .

[30YrsL8r]

Thanks for the input, folks. Probably should have updated this thread a bit more:

I struck a deal with skip665 and a rattly box of bits arrived on Saturday (a good news story for myHermes). It contained almost enough bits to build two front gearboxes/axles and a rear gearbox (my underused TL01 has donated some parts to allow me to make all three), as well as most of the parts for a Thunder Dragon-type buggy (a rear-wheel drive one, at least, that I will probably donate to my nephew eventually)

I've used the front hubs from the TL01 (turned the C-hubs upside down to move the axles out a mm or two and turned the steering arms to the front) to make my first axle. I fabricated upper arms from 3mm threaded rod (£9.99 for 5 x 1m lengths, delivered) and used the same stuff to make a drag-link steering setup. I mounted the servo on the front using the same rod, running through the holes on the gearbox for the upper arms. At the moment the gearbox is still completely stock, in case this project doesn't work out.

Like mud4fun (thanks for the comment - appreciate your input), I'm also getting binding on the drive shafts at full lock. I don't have the o-rings in yet, though. However, adding them is going to make the slight negative camber even worse.

Anyway, this is where the project is up to:

[mud4fun]

Check the link in post 1 - the axles are live and 4 linked

Wild Dagger gearboxes are another option and, as the motor's attached to the gearbox, the drive is a bit easier to arrange

Another 'cheap' option is http://www.modelsport.co.uk/?product_id=38123

Uses a lot of Axial pattern parts, so spares are pretty easy to come by

Hi TWINSET, I see you are still around. It must be what, ten years since I built thunderfoot? I remember it was you that supplied the propshafts that got me started on it. I can't believe that after this many years the truck still attracts quite a bit of interest - it is one of the most visited pages on my blog despite it being completely unrelated to restoring old Land Rovers which is what the blog is meant to be about!!

My youngest daughters, who weren't even born when I built thunderfoot, are starting to use the R/C cars now so a whole new generation of my family is starting to show interest in R/C cars and trucks, maybe they'll be on here in the next few years. Does that make you feel old???

Take care,

Ian

[mud4fun]

30YrsL8r,

You may wish to change the steering drop arm so that it runs inline with the drag link otherwise you'll be getting too much steering lock on one side and not enough on the other surely? Also you may need to use a shorter servo relay arm to reduce the amount of steering to prevent the binding on full lock. I had to do that on mine. My turning circle rivals that of the QE2 as I also locked my diffs to give maximum traction but the downside is that the truck only like to go in straight lines.....(admittedly it will go in straight lines over any obstacle...)

regards,

Ian

EDIT. If you use an adustable rod to triangulate the lower wishbones to the upper as I did (to achieve a solid axle) you can adjust the droop in the locked position to reduce the binding.

EDIT2: I will update my thunderfoot page with some more detailed photos over the weekend but in the meantime this is what I am talking about, this pic shows the steering arm and drag link on my wifes 1:1 Land Rover and I reckon that is what you need to replicate as I did with thunderfoot. http://mud4fun.files.wordpress.com/2011/08/front_axle-101.jpg

[30YrsL8r]

I can adjust the maximum steering positions from my transmitter, mud4fun, so that shouldn't be a problem.

The steering geometry may well be sub-optimal; I thought about it for a minute or two before getting on with it. My theory was that if the servo arm and the steering drop arm were perpendicular when the steering was centred, the difference (if any) would be minimal. We'll see; if it's a problem then I can turn the arm into the axle and, if necessary, move the servo our slightly to accommodate it.

I might fill the diffs with thick grease rather than lock them, at least to start with, and I'm intending to have this same axle set up at the rear, too. I'm assuming 4-wheel steering will improve manoeuvrability!

[mud4fun]

Yes, 4WS would be good. I was tempted to do same with mine but cost of those darn high torque servos put paid to that - in testing my truck I found that anything short of a huge HD servo lasted all of an hour before dying so I ended up using the huge steering servo as shown in the pics. Back in 2003 they were mega expensive so I couldn't afford 2 of them. If I was doing it again now then I would almost certainly go that route.