Tonka Winnebago RC Project

[Stormbringer]

your welcome mate 

[PraetoR]

Small update.

 

I've been working on the battery-mounting solution and looking to sort the suspension. As I said, I'm already using the stiffest springs Gmade make, for these shocks.

Unfortunately, they simply describe them as "stiff", without giving an actual rate. So, any springs I try will be guesswork, even if they are rated, because I don't know how they compare to the Gmade springs.

 

Anyway, for the front, I ordered an Injora spring pack, from Amazon. No spring rates given, but I'll simply try the stiffest ones. Unfortunately, I didn't realise they were coming from America, so they'll take a little while to get here.

 

For the rear, I ordered some brand-new, but discontinued, Axial springs, from ebay. These are Axial "yellow" AX30208, which are rated at 5.44 lbs/in. Pretty darn stiff!

As you can see, I was running maximum preload, with the Gmade springs.

 

 

 

The Axial "yellows" have far fewer coils, but are much stiffer. The difference is pretty huge.

 

 

 

I used the heaviest shock oil I had; TLR 80, which is 1000 cst! I was honestly expecting that to be waaay too thick, maybe even preventing the shock from working, properly. However, I could do with going thicker! The springs are under-damped and the shocks didn't feel that resistant. We'll see how it plays out.

 

Anyway, as you can see, the rear left has the Gmade spring (full preload) and the rear right has the Axial spring (no preload).

 

 

 

Even with maximum preload, it is very clear to see how much softer the original springs are!

 

 

 

Both sides done. Still no preload.

 

 

 

If anything, I think the truck is sitting a little higher! We'll see, once the fronts are done and the full weight of the Winnebago is introduced (batteries, weights, roof, interior, etc), I will have the opportunity to play with shock oils, as well as mounting positions. I have several of those L-brackets.

 

 

 

Anyway, that's it, for now! Cheers. 

 

 

Edited March 27 by PraetoR

[Stormbringer]

it does look to be sitting better 

[PraetoR]

I actually think it might be a little too high! Anyway, that can be played with. 

[DesignandConquer-CrystalT]

I make the 1970s Tonka Winnebago window kits. If you’re interested, look me up on Facebook.com/DesignandConquer.CrystalTarpley or email me at [email protected]

[PraetoR]

Front springs have arrived. I was hoping these Injora springs would be substantially stiffer than the Gmade springs, partially because I need them to be a lot stiffer, but also because the stiffest Injora springs are red and the second-stiffest are yellow. Red springs are modern, default, obvious and a little boring. Yellow is a little more retro-looking and interesting (at least, to me).

 

Alas, the red springs are only a little stiffer than the Gmades. I need every advantage I can get, so on went the reds.

As you can see, the fronts were on ~ 40% preload.

 

 

 

The red Injora springs weren't that much stiffer than the Gmade springs. However, I went with them, plus TLR 80 weight shock oil.

 

 

 

Front right done. Set to same level of preload as the front left.

 

 

 

Well, it seems there is a bit of a difference, after all!

 

 

 

Both done. Again, the truck is sitting a little higher, with the stiffer springs. Just like the rear.

 

 

 

Yep, overall, that's definitely a little higher. I might play around with it, because the centre of gravity is so critical.

 

 

 

Now, on to the batteries. I wanted to fit a regular-sized 3s battery, like my Overlander 4000mah hard case. However, there wasn't anywhere I could mount such a large battery, that I'd still be happy with. For example, I could strap it to the underside of the Winnebago, behind the chassis, but that would leave it too exposed and put a lot of weight further back.

 

I could, however, fit mini-sized 3s lipos, like these 2200mah soft case batteries, on the side plates. I then bought an adapter that would allow them to be wired in-parallel, which means the voltage stays at 11.1v, but the capacity is shared (making 4400mah). Having them so far out from the centre-line isn't ideal, but they are pretty light (especially, relative to the whole thing!) and they are, at-least, on the chassis, not the Winnebago. This means they will help with stability, ever so slightly.

 

 

 

To hold them in, I chopped the end of the GS02 receiver box and used the top & bottom. The top was wider (it slides over the bottom), so it was the perfect width for one of these lipos. Then, a single velcro strap could hold it in (aided by the little post on the side plate, which I made taller, by using a spacer and a screw.

 

 

 

The other side used the bottom half of the receiver box, which was narrower. The battery couldn't quite fit in. Therefore, I had to cut the side off, making that an L-shape. Still useful for positioning the lipo and having it butt-up to something. For this one, two velcro straps were needed, as this one wasn't supported on the outside edge.

 

Both batteries are utterly snug and solid.

 

 

 

Because the battery wasn't in the original battery tray, to help oppose the weight of the motor and servo, I had to add weights, to compensate. First, I weighed my original 3s hard case, which turned out to be 297.5g. OK, so for ease, I needed to add 300g to the chassis, in the original battery tray.

 

Luckily, I had strips of lead weights. Each strip weighed 60g. And, would you know it, I had 5 of them! Exactly 300g! You'd think I'd planned this (I didn't)!

Mounted the ESC and receiver amongst the lead weights (Tetris-style).

 

 

 

 

The extra 300g up-front squished the front springs, so I had to add a bit more preload. It's sitting pretty even.

 

 

 

That's a lot of weight! Look at that tyre wall!

 

 

 

Anyway, here's a video of it, as it sits! Still comically wobbly and rolly, but seems to be able to return to centre. I was deliberately throwing it about. I think she's in a pretty good place. 

 

 

 

Getting there! 

[Stormbringer]

awesome mate and agree your getting there 

[PraetoR]

I rebuilt the body and reattached the roof (no interior), to give it a proper shakedown test.

 

We've come to the conclusion that she definitely still needs thicker shock oil and stiffer front springs. We played around with preload, but it's no substitute for having the correct rate, in the first place!

 

Still, it looked great, out in the sunshine! 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Stormbringer]

does look good in the sun mate and long may it continue 

[PraetoR]

Quick update.

 

I've filled the shocks with 3000cst oil!

That isn't even meant for shocks. This is the oil I used to use in the geared diff of my Schumacher Atom 2... and I found it too thick for that! 

Anyway, it's safe to say, there is now damping, so that's good.

 

I bought the hardest springs that Element RC do for their IFS trail truck (or, did, as these are for the old model). These are 63mm long, compared to the 61mm original Gmade springs and the 60mm Injora springs. This means there will be slight preload, even when the shock collars are fully wound-out. Not an issue, I think they'll need some extra pre-load, regardless.

They are noticeably stiffer than the stiffest Injora springs.

 

 

 

I do have some old, miniature springs, which are specifically for creating dual-rate setups. They are almost the correct diameter and would work. However, the amount of preload I'd have to add to the 60+ mm springs would be obscene! It's an option, however. I could find some shorter "main" springs, if I have to. Perhaps even the same Axial set as is on the rear. Anyway, for the moment, we won't use them.

 

 

 

I'll ty this spring/oil setup and see what's what. I doubt it'll be miles away.

 

As the truck was leaning left (stationary, not centrifugal effect), I thought I'd put it on the corner weight system, to see how the weight is balanced-out and add weight, if necessary. Obviously, I expected the LHS to be heavier.

 

 

 

First measurement shows:

- Total weight of 3230g.

- 63/37% front-to-back balance. Nicely front-weighted, but, honestly, less so than I expected.

- Heavier front right, by 27g. Completely the opposite of what I expected! Why didn't it lean right, then??

- Heavier rear left, by 109g!! This DOESN'T make sense! Yes, that would perhaps explain the leaning, but, unlike the front, the rear left and right are identical!

- The RHS accounts for 52% of the weight, the LHS 48%. Again, doesn't correlate with the truck's behaviour.

 

 

 

Now, you need to know, my house is wonky! It's a badly-made ex-council house. Nothing is straight and level, things roll-off surfaces. This could account for some of the discrepancies. I repositioned the truck on the scales and tried again.

 

Second measurement shows:

- Total weight of 3229g. Only a 1g difference from before. Within tolerance.

- 63/37% front-to-back balance. Same as before.

- Heavier front left, by 30g. It was front right, by 27g, just a few seconds prior!

- Heavier rear left, by 49g. Still doesn't make sense, but it reads 60g closer than the first test!

- The RHS and LHS show 50/50 weight split. Not far off the previous 52/48 split.

 

 

 

Seeing as my house is so off-kilter, I flipped the truck and scales around, to see if it made any difference. After-all, one end of my PC desk is almost-certainly higher than the other!

 

 

 

Test number 3 shows:

- Total weight of 3228g. She's shed another gram!

- 63/37% front-to-back balance. Consistent.

- Heavier front left, again, but only by 8g, this time.

- Heavier rear left, yet again, but only by 21g. Down from 49g difference, last time.

- The RHS and LHS show 50/50 weight split, again.

 

 

 

Repositioned truck and scales, one last time.

 

Fourth and final time:

- Total weight of 3228g. Same as last time

- 63/37% front-to-back balance. We've established this to be fact.

- Heavier front right. Same as first test, but different to 2 & 3. Only 3g in it.

- Heavier rear left, yet again. This seems to be fact, but how so, I have no idea! Just under 19g different. The least, so far.

- The RHS and LHS show 50/50 weight split. This also seems to be fact (within a very small tolerance).

 

 

 

So what can we take from this?

Well...

- It weighs around 3.23kg.

- It is definitely 63% forward bias.

- It has near-perfect side-to-side weight balance. Close enough that it doesn't matter.

- The rear left is SOMEHOW heavier than the rear right, despite the fact that they are symmetrical!

- The front left and right don't weigh the same, but the difference is so minimal that the result flips, from one, to the other.

 

Honestly, I think the left/right weight differences won't matter one hoot, when this is all together. The whole rig will likely be towards the thick end of 10kg! What's a few grams, here and there?? 

 

Anyway. That's all, for now. Cheers!

 

Edited April 16 by PraetoR