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Lawsy

So I've begun rebuilding a Fighter Buggy RX from my childhood...

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Once you go lipo.....lol

I have a DT-01 Rookie Rabbit, I have always thought that the gearbox was noisy, I added bearings, changed gears and pinion and it's the same, maybe normal for model?

And yeah, LiPo is just... The word ridiculous comes to mind.

It was like adding a 200 wet shot of NOS to a standard family sedan. Or putting a turbo on a Hayabusa - you'll probably die, but with a giant smile. That's the level of stupid improvement my buggy saw today...

But then I managed to have a big front ender and broke the same suspension upright - so another layer of quicksteel is setting it back in place overnight.

And the gearbox seems much quieter with LiPo for some reason.

Oh that's right, I couldn't hear it over the laughter... I'll listen again tomorrow and see if its any more pronounced now that its dealing 50% more torque...

I just remembered I have an old phone that I might be able to charge up and put the GPS app on... Hmmm.

I also thought you were all being a bunch of soft office types, suggesting a motor limit in the 3000 - 3500kv range for the DT01, but now I'm starting understand...

In other news

The seller got back to me...

"Thanks for your message and sorry again for the wrong size of the battery.

I have contacted our related colleague for you just now.

Sorry to say this is the upgrade model of the battery,

which means the outward appearance of the battery will be like this from now on.

I can promise that the function and capacity of the battery you received is the same with the one shows in listing.

The only difference is the outward appearance.

If the battery can be used,please kindly keep it.

What is your opinion?"

Please kindly keep the wrong item that doesn't fit, even though I've paid for it already. O really?

It does not fit!!!

These people just don't even bother reading what is sent to them... It's a joke.

Possible solution

What is everyone's thinking around putting soft LiPo packs inside some sort of rigid container of the right shape? Too risky?

What if I wrapped a soft pack in a thin plastic, making it semi ridgid - wouldn't this be exactly the same as the pathetic case that is surrounding this "upgrade model"? I could even add a soft liner of some sort, and then my homemade rigid LiPo would actually be more impact resistant...

Thoughts?

EDIT: Found my old S3, Installed Speedview. If it breaks, oh well... :)

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I wouldn't even consider using a soft pack in the DT-01 because the shape and location of the battery compartment just begs for sharp debris to wedge the pack in the slot and puncture the casing. Even a normal hard case NIMH battery can get wedged in with just a few bits of gravel or small stones or rubbish in just the right place and it can be very hard to get the battery pack out again. Usually with some damage. That same situation will certainly ruin a soft pack and probably create a fire danger that could ruin your buggy. Even sand can make battery removal a real pain on this model. I'm a big fan of the DT-01 chassis with all its flaws - they are just cheap and cheerful runners and tough as old boots. The bump steer is just part of the charm, but nothing will make you curse the chassis more than half an hour spent trying to extricate a battery pack only to find you've badly damaged it after all the effort. Grrrrrrr.

Just my two cents worth, but I've got five of them and run them quite a lot. I've gotten to the point that I prefer older NiCad or NIMH batteries because they fit better. Old 2000 MAH batteries seem easier to get in and out with less problems - that very slight diameter difference seems to be the difference. And they won't burn my buggy to the ground if the casing is ruptured. BTW - I've had to replace the shrink tubing on the old packs several times for this exact reason - the debris tears the old casing to ribbons. Easy and cheap to do on non-Lipo packs though.

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I wouldn't even consider using a soft pack in the DT-01 because the shape and location of the battery compartment just begs for sharp debris to wedge the pack in the slot and puncture the casing. Even a normal hard case NIMH battery can get wedged in with just a few bits of gravel or small stones or rubbish in just the right place and it can be very hard to get the battery pack out again. Usually with some damage. That same situation will certainly ruin a soft pack and probably create a fire danger that could ruin your buggy. Even sand can make battery removal a real pain on this model. I'm a big fan of the DT-01 chassis with all its flaws - they are just cheap and cheerful runners and tough as old boots. The bump steer is just part of the charm, but nothing will make you curse the chassis more than half an hour spent trying to extricate a battery pack only to find you've badly damaged it after all the effort. Grrrrrrr.

Just my two cents worth, but I've got five of them and run them quite a lot. I've gotten to the point that I prefer older NiCad or NIMH batteries because they fit better. Old 2000 MAH batteries seem easier to get in and out with less problems - that very slight diameter difference seems to be the difference. And they won't burn my buggy to the ground if the casing is ruptured. BTW - I've had to replace the shrink tubing on the old packs several times for this exact reason - the debris tears the old casing to ribbons. Easy and cheap to do on non-Lipo packs though.

Cheers for your input mate, like the several others who have owned multiple DT01's, I certainly trust your judgement and have re-thought this one through now.

Hopefully you come back and check this reply, as I wouldn't mind knowing if you have any other suggestions for improving these things, or possible thoughts on my multi-link front end idea? I've bitten the bullet and signed up for photo bucket, so if you go back a couple of pages you should see the images to try and get an idea of where everything might sit, as well as get a feel for the geometry and strength of what I'm proposing.

It would also be good to know how have you setup your DT01's. Are you thrashing them purely because they are just so ridiculous, and thus keeping them basically stock with silver cans? Or do you also run oil dampers, Sports Tuned or brushless systems as well?

But back to the LiPo, I've revised my idea from a dodgy wrap job, to a properly protected, capped end, multiple layered, puncture resistant sleeve, with formers between the cells to keep there shape and reduce their width in order to maintain at least 1.5-2mm of clearance. It does require that I drop down to 3300mAh however, otherwise the width and thickness become an issue. If I cannot get a decent price of a LiPo that fits, I'll post details of the idea. But I think you can imagine it anyway, multipl layers of HDPE, strategically bonded between the layers (prevents crushing), some sponge tape on the cells at strategic locations, hard rubber ends and shrunk down to increase water resistance and maintain shape. I worked for an engineering firm that dealt with engineered plastics, and the puncture resistance of this idea would be higher than the comparable grenade I'm holding right now...

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I'd suggest making sure that if you build your own hard case for the battery, that you please take swelling and venting into account. As you say you've got knowledge in plastics engineering, you should have no trouble. HDPE begins to deform at 80 degrees Celsius, but I can't imagine the Lipos getting THAT hot, in comparison to NiMH/NiCd. However, it makes it easy for heat welding two half shells together.

Otherwise, I'd suggest having a look for the batteries other members use in their DT-01 cars. I guess I might have already mentioned that Lipo chassis compatibility thread, didn't I? I'm on my phone currently, so I can't double check, sorry.

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I made a few passes this morning (I'm not keen or anything, honestly...), and my straightest pass was after the battery had already lost it's edge. I'll try again tonight, and try to keep it straight on the first pass. I best up the timing from 8 to 32 while I'm at it.

But even still, we hit 60km/h on the flat, and 61km/h with a bit of hill - target achieved!

I was beginning to doubt, especially when this 3500mAh Nimh battery started accepting upwards of 4300mAh per charge from 6.9V. :blink:

This gave the false impression that it wasn't such a crap battery after all, and maybe I had a dud motor... But alas, the motor has been vindicated, and Nimh shamed in defeat.

On a fresh charge, higher timing and a straighter run, there may be a 62 in there somewhere (and I'd be seriously chuffed with 63 or 64!), but 61km/h is a perfectly fine velocity for a 20 year old, constantly crashing Fighter Buggy.

This is how things are packaged at the moment... Note, that isn't 10 degrees of toe-out, it looks worse due to the perspective and barrel distortion from the phones camera.

20160226_111931_zpsakiywiqj.jpg

And here's how we're using the wrong LiPo, with some added Chinese superlightweight-you-can-use-kindly upgrades

20160226_112513_zpsb04cyxq0.jpg

20160226_112719_zpslqqrer94.jpg

And this is the dumbest battery idea I've ever seen - even in aircraft (I have a glider, it's broken, but still). Having these top mounted and detachable cables with hard protruding lugs simply does not make sense in any application or packaging environment. To the person who came up with this idea, give yourself an uppercut, moron. If I could mount it in the normal battery holder, where it wouldn't effect how it was packaged either way, there would be the risk one of the cables being pulled out and damaging the cell, or worse, the other pulling only halfway out and being at risk of shorting. Except it's apparently how all the top tier, fully blown racing batteries are to suit those cars.

Ok great, so let's make a battery suitable for only the faster cars around, and be the cheapest LiPo available - because that's a match made in heaven for sure...

Otherwise it's still a stupid idea, in my (maybe not so) humble opinion.

20160226_112729_zpsuewi1f8s.jpg

For the sake of completeness, I'll change the pinion over the weekend and find out what it's absolute Vmax is with the 19T. Once that's done done, assuming I don't have a catastrophic crash, it will be back to the 17t pinion. I'll also drop the timing to 0 (maximum efficiency) and this should improve tyre wear a little from the slightly reduced torque.

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I'd suggest making sure that if you build your own hard case for the battery, that you please take swelling and venting into account. As you say you've got knowledge in plastics engineering, you should have no trouble. HDPE begins to deform at 80 degrees Celsius, but I can't imagine the Lipos getting THAT hot, in comparison to NiMH/NiCd. However, it makes it easy for heat welding two half shells together.

Otherwise, I'd suggest having a look for the batteries other members use in their DT-01 cars. I guess I might have already mentioned that Lipo chassis compatibility thread, didn't I? I'm on my phone currently, so I can't double check, sorry.

Hey Greg,

Yeah you posted that link, and I had already read that post several times previously as well - all of those batteries are over twice the price due to shipping downunder...

One of the other sellers has gotten back to me, and apparently they have the correctly shaped battery in stock. If the performance is the same, then I'll be a happy camper!

We used to do a lot of HDPE welding, but also using a high grade HDPE doped with an additive, it held it's shape until 85°C.

The plastic currently used for hard cases probably melts entirely by 90, softens at 65-70.

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Haha, good to hear from you :). I'm sorry about the poor availability of those stickpack shaped batteries in your area. That's too bad! Not long ago, they were even hard to come by in Europe, at least when you needed the packs not to exceed certain dimensions to fit in our beloved Tamiyas.

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Haha, good to hear from you :). I'm sorry about the poor availability of those stickpack shaped batteries in your area. That's too bad! Not long ago, they were even hard to come by in Europe, at least when you needed the packs not to exceed certain dimensions to fit in our beloved Tamiyas.

I had bit of a laugh earlier.

You mention casually (in your Madbull thread) that there is a noticeable difference between Nimh and LiPo.

As understatements go, that's a big one!

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A fresh charge and 32° timing resulted in the little-buggy-that-that-could hitting 63km/h!

Quite pleased!

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Congrats on sorting out the picture hosting.

That sounds like a great top speed. I am currently playing with a Mad Monster Hornet, basically a Hornet with Mad Bull gearbox, monster wheels and 4300kv brushless. This thread has inspired me to download a speed app to my iphone with max speed so I can test it, although mine will be on grass only I've always been interested to know how fast these Brushless models get up to. No idea how reliable it will be, although I've tested a couple of apps in car, it does seem to take a couple of seconds lag to catch up.

I see you already have the solid steering link sorted.

Keep up the good work :)

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Congrats on sorting out the picture hosting.

That sounds like a great top speed. I am currently playing with a Mad Monster Hornet, basically a Hornet with Mad Bull gearbox, monster wheels and 4300kv brushless. This thread has inspired me to download a speed app to my iphone with max speed so I can test it, although mine will be on grass only I've always been interested to know how fast these Brushless models get up to. No idea how reliable it will be, although I've tested a couple of apps in car, it does seem to take a couple of seconds lag to catch up.

I see you already have the solid steering link sorted.

Keep up the good work :)

Cheers.

That sounds like a fun mash up!

4300kv + 17t + Lipo + big wheels will net you a speed well above what I could reach, even with the 19t pinion. Though I suspect acceleration will be about the same. It's a handful on grass, though I suspect that's the tyres fault.

Regarding the GPS apps, I've played with them for years.

Firstly, one major key is to ensure the car had a straight run from start to finish, even through the braking phase (there are complex algorithms at work, and by remaining as straight as possible, you reduce the power of several variables involved in error correction and prediction).

Secondly, hold top speed for several seconds longer than you otherwise would have. Again, you're trying to reduce how many predictive calculations are being made to find your peak velocity.

Have you started a thread? I'll search it later when I'm not on my phone (unless you link me first :) )

...

Today I flipped it over and snapped the body shell, just in front of the driver cabin... Argh..

As such, LiPo is back on the shelf because the front post was the thing keeping the shell down, and the shell was protecting the battery.

No protection; no Lipo - it's not worth the risk of puncture.

Although I miss the power, it must be said that having a lower centre of gravity again brought back the relaxing side of RC bashing. You can throw it around, induce big tank slappers and generally drive like a dick and get away with it.

I've also removed the meccano, and with the current wheels and tyres being larger in diameter, the stock suspension angle handles better (purely a centre of gravity thing, it sits 10mm lower without the meccano). This wasn't an issue with the smaller diameter on-road wheels, since the increased spring rate was more beneficial than the reduced centre of gravity.

I've also cut some aluminium sheet into a few funny shapes to mount the dampers lower on the gearbox. I'll put some pictures up later, but so far I can already see how this could really improve roll resistance while leaving the effective spring rate fairly constant, which has always been the goal.

It will, however, require a heavier damper fluid, and likely the CVA supplied springs. This is because the wheels will have additional leverage over the suspension, and so a higher spring rate and increased damping effect will be required to keep things balanced. We'll see whether or not I get the chance to finish this and run a useable setup tomorrow. Should be fun!

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Well I managed a mere 22mph out of the Hornet on grass and 25mph on the same setup WT01. I don't think I'm able to hold the speed long enough for the app to record properly, it takes about 5 seconds to get up to speed from testing in cars so I'm not convinced thats accurate. Not sure if the app is that great not helped maybe by my lack of 3g?

Ps. No thread yet.

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Hmmm, try and find an app called speedview (it's on android anyway, might also be on Apple's app store). I've found it most accurate, repeatable, and verifiable in other testing (0-100km/h and 0-400m testing from various people, which are more difficult, and also point to point testing).

On grass I would expect you to lose a lot of speed without tyres specifically designed for it.

But even so, I would have expected you to go quicker than that with standard monster truck tyres (with such a large diameter), and with a set of massive spiked off road tyres, running on smooth grass and a nice long run, I'm not sure. Maybe within 5%-15 of your tarmac Vmax? But not miss it by 30-40%...

Feel free to hijack here and post pictures :)

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Thanks, the app I bought was called speedometer. I'll take a look for the one you mentioned. The problem I've got is although I can hit full speed in my garden, I can't hold it for long enough for the app to pick up. Had a run with the Hornet after posting and with different tyres and it flies now, just hard to secure the phone to it!

I've put some pics in the what have you done today thread.

Cheers

Nito

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Thanks, the app I bought was called speedometer. I'll take a look for the one you mentioned. The problem I've got is although I can hit full speed in my garden, I can't hold it for long enough for the app to pick up. Had a run with the Hornet after posting and with different tyres and it flies now, just hard to secure the phone to it!

I've put some pics in the what have you done today thread.

Cheers

Nito

I remember your garden from the the 4x4x4 build thread. There should be enough space if you use speedview if you turn off GPS filtering.

I would try and find someone with an Android phone, preferably Samsung or HTC since they tend to use better GPS receivers (so I've heard). Download speedview for free, put it inside a snap-lock sandwhich bag and cable tie it under the shell - if the shell sits up, cable tie that instead of using the R clips - it's only for a few runs over a few days, so if you burn through a pack of cable ties over the coarse of a week, who cares, right?

Back to GPS filtering - basically, GPS filtering turns the app into a sort of raw mode. It allows transient spikes to be recorded instead of filtering them out, since changes in the current set of satellites, signal quality variation due to obstacles, or a host of other causes can cause transient spikes in the speed. Almost every GPS app worth using has some sort of filter like this because you want this filter most of the time.

However, this is not most of the time. You want to run a tonne of passes over a short distance, with acceleration rates well beyond the transient filter threshold. By running multiple passes you can then get a feel for what was reality and what was possibly a position error, by averaging the results (you become your own filter). This works because you will see the peak speeds that would normally have been discarded as impossible in anything but a hypercar - and it suggests turning filtering off if you drive a Veyron. Personally, I'm more partial to the One:1, but I digress. I believe this will give you a very good result (at worst, +/-2km/h).

...

Today, I finished cutting almost-doodle-like-shapes out of 0.5mm aluminium and drilled various holes to mount the damper, and although I had a bit of a mathematical fail with my first two attempts, I'm fairly close with my 3rd. Not entirely happy with it still, but the car sits up without fully compressing the springs, and that's a start.

th_20160228_214639_zpskblm19j3.jpg

The key to what I'm doing is increasing the vertical component of the arcs formed by the lower suspension mount during movement, and that's really all it is. The standard mounting position is significantly above the point of rotation, so much so that there is almost as much horizontal movement as there is vertical during gearbox rotation. Combined with how flat laying the dampers are, the vertical component of the damper movement translates into almost zero damper compression, which in turn means there is basically no anti-roll in the rear suspension at all. Think of how much vertical change there is in the arc formed between 11 and 12 O'clock - there's not much.

However, if the damper is mounted lower on the gearbox (almost inline with the point of rotation on the horizontal plane), then the vertical component of the arc formed by gearbox rotation is significantly greater than the horizontal component. This also increases the angle the dampers from horizontal, and this all results in at least some rotational resistance. Think of this as the vertical component of the arc between 9 and 10 O'clock - almost the entire movement is vertical.

Another key point to all of this is the width. If I can reasonable increase the distance between the damper mounting points, I can further increase the leverage the dampers can apply in resisting rotation. This is a little more difficult as it requires spacing the top mounting points a well, and this fouls on the body. I'm already at that point as is, so I'm not sure how much wider I can get - however I'll try and get as much as is physically possible.

th_20160228_214807_zps5nn5veh3.jpg

There is one thing working against things here, and that is the exact same principle as the above, except now looking at the side of the gearbox, and not the rear.

By moving the damper mount lower and in front of the axles, the initial movement of the dampers resists almost zero compression as there is little movement along the dampers axis. The gearbox also has a lot more leverage over the dampers. The fix here is to move the top mount rearward slightly, however I don't really want to do that as it adds weight in precisely the place I don't want any, but we'll see.

The side benefit of the gearbox having more leverage over the dampers is that it does allow me to run the hardest spring rates, which helps anti-roll even further. I have all three pre-load collars installed, and yet the effective rate at the wheels is softer than stock. When I figure out the best position I'll post pictures.

Until then, feel sorry for my Fighter Buggy shell - punished for 4 of its 21 years in existence, it has finally succumbed to its injuries :(

th_20160228_223641_zps7d6qexr3.jpg

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Thanks for that GPS info, I checked out that app, looks good but I need to upgrade the software on my phone before I can run it, this might actually oush me to get around to upgrading it finally. My Fighter Buggy RX shell is the opposite if yours, it has a front end but not the back end!!

If it's any consolation, I also wrecked my lovely new Hornet shell at the weekend. Looks like a 25 year old basher shell. It's only had about 4 battery packs through it but with the brushless setup it's running it has done some spectacular stunts that I didn't even know where possible, like 10x simultaneous cart wheels as well as multiple forward flips end to end and all sorts!

medium.image.jpg.cda6f213763e16624d4b0f3

Ignore the front wheels, thought I'd give them a try but it's better with bigger wheels up front!

1 run earlier...

medium.image.jpg.df64883ba02cb4b10950234

Cheers

Nito

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Crash acrobatics usually have you cringing and in awe, at the same time.

That looks like it could be quite a ridiculous amount of fun though! Have you clocked it at a higher speed to get a ballpark figure?

Sorry about the shell however...

After trying to buy this Lipo 3 times from various vendors, I've been refunded twice before anything was shipped, for "reasons". Argh...

Still haven't had a chance to run the modified rear suspension position. It feels a bit soft for my liking though so I may drill one more hole slightly higher first. This will reduce roll resistance however, so I'm keen to run thicker damper fluid in this position first to see if I can critically dampen the rear a bit and get away with it, without too many side effects. Hopefully I get a chance this weekend to test it!

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Well,it was a bit of a nightmare involving me staying up until 1am mucking about with updates and restores but I'm pleased to say I'm all updated now and have the app installed, it seems quite impressive so I look forward to trying it at the weekend. It's the third app I've bought and the best by far so thanks for the tip!

As soon as I have a result I'll post it up. I can't turn filtering off on my one (iphone) but it is now set to 2 decimal places and turned on to max accuracy. We'll see, there is a bit of lag in the car but it is definately quicker than the last app speedo and although it lags, it also seems to pick up the peaks albeit a couple of seconds later even if it was a momentary peak and immediately hit the brakes which I tried on my way home tonight!

Cheers

Nito

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Hey that sounds good. You may even want to try loosening up the minimum accuracy after trying the current setup, I personally have mine set to reject over 20m position errors per satellite.

I have the free version and that's the only accuracy setting available. But typically, only satellites with a position error of about 3m or less are used, and when on the move and all of the fancy software voodoo kicks in, it drops to about 1m. Therefore, this error rejection rarely kicks in.

Without a ground level base station, and a horizontal (self leveling if on a moving target), high gain GPS antenna, that's about the best one can expect (physics says so).

Now, even though the more advanced error correction algorithms allow short distance measurement with an acceptable degree of accuracy, nothing beats having an excessive amount of raw data for computing the best averages (dead straight runs at Vmax for as long as possible). Your best bet is to find a nice park and give both your car, and the GPS system, a chance to hold Vmax for a few seconds.

It's also possible to export the data, which should make it easier to tell the quality of your data, though I've never bothered...

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I had an idea, buy yourself a small free standing net from a sports store - The softest, most-likely-to-not-damage-an-RC-car-at-top-speed type of net you can find.

I think you know what to do next :)

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I already did that with a 5 bar gate!

Haha, not exactly what I had in mind!

Any further results?

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Ouch, that's a pity, pushing the limits I guess. At least a new tub is readily available and not too dear.

My Hornet looks a wreck now, the app is good but only managed 25mph.

1012B3E7-160F-4E80-888C-C9614F8DBD60_zps

The garden is not long enough to reach full speed on, as the trace shows, the speed isn't levelling out. It's hard work reaching even those speeds in the bumpy terrain and the slightest bit of full throttle and it flips over at pretty much any speed as a consequence of the front bouncing on bumps giving it some air which then takes little throttle to flip.

I'm rapidly coming to the conclusion that the Hornet really isn't built for this, it is so light especially with a lipo and it's just too much power for the chassis. The good news is apart from too much power, the handling is actually pretty good, I'm going to put the stock gearbox motor back on it with a brushed motor. The big wheels are a great improvement though so it'll be nice to have a big wheeled runner instead of just for display in my cabinet. I have a spare unbuilt Hornet metallic edition so I will need a new black shell to complete my cabinet line up though!

The brushless motor will be reasigned to the Aero Avante for now I think.

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Take it on the road and determine your tarmac speed first!

And new tub you say?

A log of QuikSteel might have something to say about that...

The break was a combination of a few things.

Firstly, I rebuilt all the dampers, and this increased their effect significantly, providing slightly higher corner speeds and more turn in.

Secondly, brushless plus lipo equals speed, and full compression bumps at speed involve a lot of force.

And finally, I spaced the mounting point too far from the upright, significantly increasing the moment around the joint.

Add in another big cartwheel on tarmac, to get the ball rolling, and some very high speeds (high frequency bumps) thereafter, and you've got yourself a split upright, some swearing, and sad faces all around...

I'll try and bodge up a fix this week sometime and see how it goes.

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