TheRCRacer Active Floating towers

Looking at several new touring cars, there seems to be a movement towards alloy horns. These are not new like everything in RC. I first came across them with the Corally HMX. However, with these designs currently in vouge it got me thinking about my version of the 'Horn' concept that some readers will remember that I explored a few years ago. The key difference is my horns would move up and down. Essentially an active floating tower.So I dug out my retired TRF419 wet car that had the latest version of a floating towers you can have a look. What are they all about?Well the the theory behind these towers was that the rebound stroke of the shocks is constrained in some part by the rate in which the piston can move through the oil, and to an even smaller amount by the amount that the spring returns to neutral after being compressed. The basic animation above shows the theory in practice. This exaggerates the concept, but you can see when the bump falls away the piston (Red), still has to make its way back through the oil at a similar rate to when it goes up.As you would expect, if you run a stiff car on a high grip smooth track this really is not much of an issue, however on medium to low grip, bumpy tracks there could be potentially some benefit. Following a thread of discussion on a Formula One engineering forum and, coincidently spotting some interesting images of Tamiya TRF works drivers running cut towers. I felt inspired to create a solution that could eliminate almost all of the rebound stroke constraints to ensure that the tyre would stay in contact with the track after any sudden bumps, or when the car would be unsettled on a rapid switchback or kerb. As suspension compresses the suspension arms raise towards the shock tower. After the bump the suspension arm is pushed back down via the spring. The internal shock piston will provide resistance on the way down, slowing down the speed that the arm can ultimately fall. So I had to make the arm fall without being constrained by the shock oil.To achieve this in principle was quite simple. The towers would need to be independent, they would stay in place when they are being pushed up against, but they are not fixed from falling downward. So each corner of the car will fall along with the lower wishbone, allowing the tyre to hit the ground quickly. Then as the spring and piston returns to neutral the tower will will return to their starting position. This is show in the animation above. It was important that the downward movement is as fast and smooth as possible so designed the parts to operate on a bearing. As you can see they mount on the car in the place of the shock towers. This is fine although you do need a solution for the rear body posts. Again this was also an easy fix as I just mounted the rear shock tower on the rear bulkhead and used 3mm spacers. This gives you rear facing body posts, although you could just stick upward posts on easily enough. However for TRF cars with Low profile shocks (TRF420, TRF419X & TRF419XR), you need to run a special brace to ensure that the rear tower can clear the dampers.I tested these on a variety of race tracks in differing conditions with my TRF419 in 2018 and I found that the car did have quite a lot of grip. Although it was always hard to really get an accurate result on the progress as the damp / dusty / bumpy tracks would always have changeable evolving levels of grip.I kept tweaking the design and by the end of 2018 they have pretty much stayed as they are. They main change was moving to a 8x3x4mm flanged bearing. This gave great durability and also allowed the towers to be stronger as they were 3.5mm thick. Since 2018 /2019 I haven't used these as I have not managed a lot of outdoor running on anything other than a smooth prepped race track. It was only recently when running with friends at a local outdoor temporary race track where I suffered from grip that I actually got seriously thinking about these towers again. I only run a TRF417 on the unprepared track so I tweaked the original drawings for the TRF417 suspension geometry. I was looking forward to seeing if they made much of an impact, but it was rained off, so instead I thought why not try them on low grip carpet. Whilst not outdoors, it is still tight so rapid switchbacks and the occasional bump in the carpet will test the towers.At the TrackFrom the first round the effect on the handling was noticeable. The car did roll a little more than normal in the tighter parts of the track, however the car still had a lot of grip and steering. I managed the fastest time for that round by a comfortable margin, primarily as the car seemed to make up for the lack of grip that the tyres usually provide when on a green track.I made a few more set-up adjustments for the second round. Bringing the rear shocks inward and reducing droop a little. The car was very quick from the start,  nothing could touch it and the adjustments helped the car to feel even more hooked

TheRCRacer Active Floating towers
Looking at several new touring cars, there seems to be a movement towards alloy horns. These are not new like everything in RC. I first came across them with the Corally HMX. However, with these designs currently in vouge it got me thinking about my version of the 'Horn' concept that some readers will remember that I explored a few years ago. The key difference is my horns would move up and down. Essentially an active floating tower.

So I dug out my retired TRF419 wet car that had the latest version of a floating towers you can have a look. 

What are they all about?

Well the the theory behind these towers was that the rebound stroke of the shocks is constrained in some part by the rate in which the piston can move through the oil, and to an even smaller amount by the amount that the spring returns to neutral after being compressed. 

The basic animation above shows the theory in practice. This exaggerates the concept, but you can see when the bump falls away the piston (Red), still has to make its way back through the oil at a similar rate to when it goes up.

As you would expect, if you run a stiff car on a high grip smooth track this really is not much of an issue, however on medium to low grip, bumpy tracks there could be potentially some benefit. 

Following a thread of discussion on a Formula One engineering forum and, coincidently spotting some interesting images of Tamiya TRF works drivers running cut towers. I felt inspired to create a solution that could eliminate almost all of the rebound stroke constraints to ensure that the tyre would stay in contact with the track after any sudden bumps, or when the car would be unsettled on a rapid switchback or kerb. 

As suspension compresses the suspension arms raise towards the shock tower. After the bump the suspension arm is pushed back down via the spring. The internal shock piston will provide resistance on the way down, slowing down the speed that the arm can ultimately fall. So I had to make the arm fall without being constrained by the shock oil.


To achieve this in principle was quite simple. The towers would need to be independent, they would stay in place when they are being pushed up against, but they are not fixed from falling downward. So each corner of the car will fall along with the lower wishbone, allowing the tyre to hit the ground quickly. Then as the spring and piston returns to neutral the tower will will return to their starting position. This is show in the animation above. 

It was important that the downward movement is as fast and smooth as possible so designed the parts to operate on a bearing. 

As you can see they mount on the car in the place of the shock towers. This is fine although you do need a solution for the rear body posts. Again this was also an easy fix as I just mounted the rear shock tower on the rear bulkhead and used 3mm spacers. This gives you rear facing body posts, although you could just stick upward posts on easily enough. However for TRF cars with Low profile shocks (TRF420, TRF419X & TRF419XR), you need to run a special brace to ensure that the rear tower can clear the dampers.

I tested these on a variety of race tracks in differing conditions with my TRF419 in 2018 and I found that the car did have quite a lot of grip. Although it was always hard to really get an accurate result on the progress as the damp / dusty / bumpy tracks would always have changeable evolving levels of grip.

I kept tweaking the design and by the end of 2018 they have pretty much stayed as they are. They main change was moving to a 8x3x4mm flanged bearing. This gave great durability and also allowed the towers to be stronger as they were 3.5mm thick. Since 2018 /2019 I haven't used these as I have not managed a lot of outdoor running on anything other than a smooth prepped race track. 

It was only recently when running with friends at a local outdoor temporary race track where I suffered from grip that I actually got seriously thinking about these towers again. I only run a TRF417 on the unprepared track so I tweaked the original drawings for the TRF417 suspension geometry. 

I was looking forward to seeing if they made much of an impact, but it was rained off, so instead I thought why not try them on low grip carpet. Whilst not outdoors, it is still tight so rapid switchbacks and the occasional bump in the carpet will test the towers.

At the Track

From the first round the effect on the handling was noticeable. The car did roll a little more than normal in the tighter parts of the track, however the car still had a lot of grip and steering. I managed the fastest time for that round by a comfortable margin, primarily as the car seemed to make up for the lack of grip that the tyres usually provide when on a green track.

I made a few more set-up adjustments for the second round. Bringing the rear shocks inward and reducing droop a little. The car was very quick from the start,  nothing could touch it and the adjustments helped the car to feel even more hooked up. I improved my best time by over 10 seconds. Importantly the tyres really seemed to be working much better than previous weeks. 

In the third round the car again was flying.. I was improving on my previous time until I experienced a major thumb failure and hit the boards at top speed. The car felt ok so I continued, a couple of laps later a gentle nudge from a lapped car launched me into more track markers and the front of the car was leaning to the left so I had to retire. 

It was easy to spot the issue. One of the active tower lugs had snapped so the left front had no stopper so it would raise up. The stoppers were only small, but worked fine outdoors, however for the rough and tumble of indoor club racing I was going to need to modify them for more strength.

This allowed me to do something I hadn’t tried before. Running a hybrid of both the original towers (At the front), alongside the active towers at the rear. 

Round 4 started and the TRF raced off, the car felt good and the rear active tower still worked wonders in keeping the car feeling both responsive yet planted. The grip had come up as the night progressed, although a swift track layout change between heats had made matching comparable times redundant. The TRF left the other chassis behind as it stormed to the fastest time of the round.

The final round started even stronger, I was beating my personal best until I’m was hit hard from behind, initially not a problem, but after the third hit I suffered the same issues as before, the locator pin had snapped off so the rear balance was off. I retired but happy in the knowledge that these parts had found some extra speed over my normal set-up, and I came away from the night with the fastest time of the day by over 10 seconds.

Strengthening update : I made a few tweaks to the design after this test session. I can happily report that the the new locators are much more beefy following the second test indoor test session and the towers surviving some very hard hits. I suffered no damage to the towers at all.. even when I bent a front suspension block!


Next steps.

I have made a set for the TRF420, this is to try on high grip carpet, just to see if they make any noticeable impact on the lap times.

These are for the SSBB low profile shocks

The TRF420 and TRF419X&TRF419XR sets include a rear bulkhead mount that you attach the rear tower to, this allows the low profile tower to clear the shocks. You will need two 10mm screws to attach it to the bulkhead. 

Want to try these?

Like all these things I will make them available to you to try. There will be a range to download, just click on the links below when they are available (Later this week, when I have time). 
  • TRF415 series (Download Link). (Contents 4 towers) 
  • TRF417 series (Download Link) (contents 4 towers) 
  • TRF418/TRF419 (Download Link) (Contents 4 towers) 
  • TRF419X/TRF419XR (Download Link) (Contents 4 towers, rear bulkhead mount for tower)
  • TRF420 (Download link). (Contents, 4 towers, Rear bulkhead mount for tower).
  • Xray T4 (Download link)
  • ARC (Download link)

Overall I'm pretty happy with these towers, the downwards movement is faster than a standard shock tower. I have some non-3D printed versions in development that carry on the same design principle.


Help develop more parts

If you appreciate the non profit work I have done, please feel free to tip me to help me to afford to develop more parts. You can make a Tip by clicking this link https://www.buymeacoffee.com/TheRcRacer


Disclaimer and thanks

These have been made as a contribution to the Tamiya racing community. There is no profit for myself. These are just a tuning aid.

I have invested my own time and money in these parts for the Tamiya and wider racing community, at no profit for myself. These designs are always helped via feedback from other racers. So please let's share feedback and set-ups and I can try to refine or design other parts in the future :) 

I own the design, and copyright and manufacturing rights to these parts so please do not copy them and sell them for profit.



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