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@djmcnz thanks for the advice - this is the kind of arcane knowledge I need.  I've hunted around for books and online information about suspension tuning but I can only ever find the very basics - it seems this info exists in people's heads and they're happy to share when asked but it's not easy to find a single resource to check from.  I'd happily write a book about the subject if only I knew anything about it :D

I'm planning on doing the Friday test day at Revival so I'll definitely try adding preload.  I do plan to rebuild the shocks before I go as I have no idea what oil is in them.  Do you have a good starting point?

Here we stumble on one of my other bugbears of RC racing - finding good shocks.  Ebay is stuffed full of budget alloy shocks provided with no specs and which no known spring will fit.  There are TRF if you want to spend the money.  I'm told Schumacher shocks are great and have plenty of spring options but I don't know if they're sold as sets or if I have to track down part numbers from a car manual.

The shocks on this car came with it, but they're identical to those on my WR-01 and TXT-1, which originally came as a set of 8 way back when.  I think they were for an E-maxx or something else with 8 shocks.  Again, they have no specs and none of my other springs fit.  I'm wondering if I should switch to CVAs because they at least have a common spring fitment.  I'd fit TRF if I could afford it ;) 

Anyway - thanks again for the info.  If I can find myself an experienced racer at the Revival then I will tag myself onto them for setup advice :)

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NP & thank you.

Tuning is very subjective, that's why you'll typically get vague answers, or none at all. There are some common tips that are worth sharing when the subject comes up.

Not knowing what oil is in them is a challenge. You need to get a baseline, drain and rinse oil, put your preferred (known-quantity) in and adjust as you see fit. The key is a baseline that you know the parameters of.

Edit: you may not need to change the springs, start with the oil and preload, that's cheap.

Edit #2: I recommend you pick any (reputable) brand of oil and run it for a few years to get used to the changes in viscosity. Once you can "feel" this, then you can cross brands quite easily. To be honest the low consumption rates make even Tamiya oil affordable for shocks.

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Thanks again @djmcnz.  I've been using Tamiya brand oil for years in all new shocks I build, if I'm doing buggies I tend to start with soft.  I don't think I ever refilled the shocks on the TF since I got it, but if I did it will be Tamiya oil and therefore it will be coloured.

I think I might be running low on Tamiya oil, so I'll have to see if I can get any more.  I get the bit about sticking to a brand - I've heard that different brands can have very different viscosities despite having the exact same number on the bottle.

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Sunday 18th July, 2 weeks to Revival and my batteries keep falling out.  This car came to me with this chassis and these battery straps, and they were working fine but suddenly they aren't.  Even a quick jaunt around the lawn and the battery flops off and unbalances the car.  That's no good for a race car!

sm_P7180011.jpg

Unfortunately, I didn't have anything else that would fit, and couldn't work out a modified battery clip that wasn't going to take the entire day to make and add several grams in weight.  So an order was placed for some generic 10mm Velcro strip, and everything went back in the box for another week.

Most disappointing thread update ever?

 

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4 minutes ago, Mad Ax said:

Unfortunately, I didn't have anything else that would fit, and couldn't work out a modified battery clip that wasn't going to take the entire day to make and add several grams in weight.  So an order was placed for some generic 10mm Velcro strip, and everything went back in the box for another week.

I remember back in the day (early 90's) that I busted a plastic clip in a car on car tangle and jury-rigged a replacement with some thin "coat hanger" wire for the finals. Worked okay.

If you have the stock spars you should be able to use any TA02 ends, the strap method sucks with this chassis and rounded batteries.  

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So apparently, if you hit "show reply" while typing a reply, you lose your reply...

2 minutes ago, djmcnz said:

If you have the stock spars you should be able to use any TA02 ends, the strap method sucks with this chassis and rounded batteries.  

This chassis is (I think) a HPI hop-up, it's not an original Top Force plan, so there's nowhere to attach the normal TA02 battery clips.  I have the Top Force tree with the stock end caps but the bottom of the chassis is narrow, so there's nowhere to put them.  I briefly considered trying to get a shorty in, but it would take more time than I have to make it work.

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8 minutes ago, Mad Ax said:

So apparently, if you hit "show reply" while typing a reply, you lose your reply...

This chassis is (I think) a HPI hop-up, it's not an original Top Force plan, so there's nowhere to attach the normal TA02 battery clips.  I have the Top Force tree with the stock end caps but the bottom of the chassis is narrow, so there's nowhere to put them.  I briefly considered trying to get a shorty in, but it would take more time than I have to make it work.

Right, if I'd taken some time to look back in the thread I probably would have seen that.

So, if you're forced into using straps, I'd recommend putting a piece of adhesive Velcro (loop side) on the battery and the corresponding (hook) side on the inside of the strap - at both ends, top and bottom. This way you're not primarily relying on the strap tension to keep the battery in place, rather the grip of the Velcro.

If that makes no sense at all but you're still interested 😂 feel free to hit me up for more info.

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That makes perfect sense @djmcnz, I'll be taking some super-strong Velcro tape with me so I can do this if I have problems.  I haven't got around to entering the latest update (I was typing it out but I lost it and don't have time to re-type it now) but I did get some new 10mm tape which I've cut with longer tails, so it's easier to get a tighter fit on it.

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Here's the new Velcro tape that arrived last week.  It seems to do the trick, but adding some adhesive Velcro onto the battery wouldn't hurt either.  I'll also be taking some of that really tough battery tape that I use in various touring cars in case this fails.

sm_P7250050.jpg

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In other news, I ordered a Jazrider alloy steering set to replace the alloy set currently on there.  It's very old and loose and floppy and has loads of play.  The Jazrider set arrived earlier than anticipated (from Germany, apparently, the ebay listing said it was in the UK but I fully expected it to come from China).

The Jazrider set is quite different to the stock / stock-a-like alloy product I have.  It curves the pivots inboard, presumably to reduce bump steer.  It also doesn't have a turnbuckle centre link, it has a solid alloy one.  I guess that isn't a problem (I have literally never adjusted the centre link) but it does look a bit flimsy, I wonder if it could break in a big impact?

Anyway: here's my old setup:

sm_P7250045.jpg

And here's the Jazrider setup, installed:

sm_P7250046.jpg

umm, yeh, OK, will need to find some longer rod-ends...

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But there's another problem.  My Top Force has an alloy spacer under the front transmission case.  I'm not exactly sure what this is for, but could be anti-squat.  There's an angled anti-squat bracket under the rear transmission case too.  These will help to angle the car forwards.

The Jazrider pivots hit the spacer on full lock, reducing steering throw.

sm_P7250047.jpg

I thought about flipping the unit upside down and reversing the servo, but the crank hits the gearbox support.

sm_P7250048.jpg

meh

sm_P7250049.jpg

In the end I solved the problem in the most sensible way possible: I took the 850 bearings from the new Jazrider set and put them in the old alloy set.  That killed all the slop and gave the old set a new lease of life.  I also replaced the old turnbuckle with a shiny new titanium one.

So - that's the Top Force all nicely sorted ready for racing on Sunday.  In between writing the Manta Force update and this one, the weather forecast has changed and it's now looking like a dry weekend after all.  Fingers crossed I can the old Evo on track :) 

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Wow - no updates for over 2 years!  Casting my mind back to Revival 2021, I think I only ran the Manta Ray - it was wet when I arrived on the Friday for practice, so I got the Manta Ray dialled in on track, and after it dried in time for race day I realised I didn't want to have to learn a new car all over again, so the Top Force stayed in the box.

It did get raced at Revival 2022, on Broxtowe's vicious astro-with-concrete-pillars track.  The organisers even threw in a little grass loop, just to keep us all on our toes, and naturally we had a bit of rain too.  The Top Force went sort of OK, but still suffers from that sort of general wooliness that it's had for a few years, and is probably down to virtually every moving component being badly worn.

Anyway, it got me as far as the final, and half way through the race, it started emitting a loud screeching sound.  I thought it was something in the transmission, and at that point, I figured I'd just keep the throttle in and to heck with it all.  It was the last race of the day anyway - if I retired before it died, I'd be going home with a broken car, if I ran it until it died, I'd still be going home with a broken car.  Well, the screeching got worse and worse, and it started to feel like I was driving with a loose slipper clutch, but it never actually stopped working.  The TFE doesn't have a slipper, but surely a skipping spur would have given up completely after a lap or two?  But no, it just kept on going, screaming like a banshee, until the buzzer sounded and we all breathed a sigh of relief.

And, after that, I completely forgot about it.

A couple of weeks ago I got it down off the shelf to give it a once-over before the Tamiya Junkies meet, and when I span it up on the bench, I heard the screeching noise.  Everything seemed to be moving smoothly enough, but on full throttle, it would scream.  I mean, really, really loud screaming, like as bad as when you take a toddler to the park to see the ducks and there aren't any ducks.

I've had some trouble with failed bearings in motors recently, so I pulled out the motor and span it up, and it was totally fine.  Smooth, quiet, no nasty noises.  So it had to be in the transmission.

So then I pulled out the idler, and ran it with just the spur in place.  Still screeching.

Count it be the pinion mesh?  Well, it's in the right position, according to the diagram, and it doesn't feel excessively tight.

Spur bearing?  Replaced with spares, still just as bad.

Hmm...

Then I noticed, when it's screeching, the wheels take a while to get up to speed.  Just like the slipper is slipping...

OK, let's pull the motor apart...

Here it is - it's pretty old now, over 10 years, from an Etronix Photon combo that I bought when I first started buggy racing (with a then current RC10 B4.11 Worlds Factory Team car - that's a mouthful!) which has been installed in various cars since then.

sm_PA010447.jpeg

And here's the innards!  That big long fat silver thing between the two end caps is the magnet, and it's supposed to be bonded to the shaft.

sm_PA010448.jpeg

Except it isn't.  Whatever they bonded it with has obviously denatured in the heat and come away.  I tried to drift the end caps off so I could get some new epoxy right into the shaft itself, but they wouldn't budge, so in the end I managed to drag the epoxy into the gaps between the caps by lifting up streamers with a mixing stick and turning the shaft through it.

sm_PA010449.jpeg

I left it to cure for a few days, then trimmed off the excess and stuck it back together.  It runs now, with no screeching or other unpleasant effects, but time will tell how well it survives.  The epoxy is very, very old, and has been open for a long time (although not mixed, obviously) and remains slightly sticky even after several days, so it may not be curing properly.  Perhaps the heat of the motor will help it cure, or it might just melt it off.  Time will tell - I'll give it some tracktime on Saturday and see how it goes...

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