Aim of Side Impact Structure

[blister]

Hello,

What is in your opinion the intent of the side impact structure? Is it a crush zone which absorbs energy or is it a rigid structure that will not allow any deflection?

The FSE rules state, that you have to have two side impact structures if you mount the accumulators on the side of the drivers. This makes it nearly impossible to have a nice package with side mounted accumulators and a monocoque structure.

I think the event organisation should more focus on hub motors mentioned with no words in the rules and electric motors used as a rear crash bulkheads. I have never seen a car crashing into the side of another. But i have seen a dozen of cars loosing a wheel including upright and at least three collisions, where a car drives in the back of another. I don`t want to be the driver who drives into a 1.5mm carbon shell and behind of that are 300V.

[blister]

Hello,

What is in your opinion the intent of the side impact structure? Is it a crush zone which absorbs energy or is it a rigid structure that will not allow any deflection?

The FSE rules state, that you have to have two side impact structures if you mount the accumulators on the side of the drivers. This makes it nearly impossible to have a nice package with side mounted accumulators and a monocoque structure.

I think the event organisation should more focus on hub motors mentioned with no words in the rules and electric motors used as a rear crash bulkheads. I have never seen a car crashing into the side of another. But i have seen a dozen of cars loosing a wheel including upright and at least three collisions, where a car drives in the back of another. I don`t want to be the driver who drives into a 1.5mm carbon shell and behind of that are 300V.

[Crispy]

I'm not an expert, but it seems that electric motors are less likely to explode and/or cause fires than batteries. Many accumulators are essentially small bombs. I can understand why they want them well protected.

youtube "lipo explosion montage", then imagine 50+ kilograms of that stuff. Could produce some spectacular fireworks.

[Bemo]

Of cours it makes sense to protect the accumulators from getting physically damaged. But it is correct, that the motors should be well protected too.
If a car gets hit from behind and the motors are the part that get hit there might be ripped of cables with several hundred volts. That's definitely dangerous too.

[Crispy]

Perhaps they are expecting the IMD to disable the high voltage system in the case of a damaged motor. I'm not sure if this is a reasonable expectation or not. In either case, is does seem that the batteries are more dangerous than the motors.

I won't argue that motors don't need any protection. I'm just not surprised that there is a higher standard for accumulators.

[Bemo]

Definitely true. But in the worst case the IMD detects a short curcuit after 20 seconds then it may take up to five seconds until voltage dropped below 60V. That means that it is possible, that there is high voltage on a ripped off cable for almost half a minute. I think a rule which says that the motors have to be within the frame structure would make sense.
But of course the accumulators are more dangerous. If their container gets damaged there is no possibility to should down high voltage anymore! So in my opinion it is absolutely necessary that they have to be within the side impact structure to make sure that this won't happen.

[blister]

I am not saying that the accumulators should be outside of the side impact structure. But i don`t understand why there has to be a second one on the inside of the accumulators (so on each side of the accumulators a side impact structure).

My Problem is: "Yeah in a crash situation, the outer side impact structure will break, but the INNER one will whitstand the forces for sure."

In my opinion on the inside of the accumulator packs ther should be only a firewall/isolation wall with a metallic surface and non-flammable material. A structural side impact structure is therefore in my opinion not incraesing the safety.

Basically this rule makes it nearly impossible to find a nice solution for a side mounted part of the accumulator box with a monocoque structure.

[Crispy]

Purely on opinion at this point, but I would want a pretty substantial firewall between me and the batteries, and preferably one with some structure to it. Perhaps they liked the simplicity of using the side impact specification for this task.

Either way, it seems like it would require a pretty crazy chassis to fit accumulators inside the monocoque next to the driver. Sidewinder maybe? That could be slick.

Although, if there was a motor right next to me I would want a substantial barrier as well.

[Thrainer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Crispy:
Purely on opinion at this point, but I would want a pretty substantial firewall between me and the batteries, and preferably one with some structure to it. ...

Either way, it seems like it would require a pretty crazy chassis to fit accumulators inside the monocoque next to the driver. ... </div></BLOCKQUOTE>

Hi Chris,

if we replace "batteries" with "fuel", does your opinion change? I haven't found any word in the rules outlawing a fuel tank between the side impact structure and the driver. Is 5 l of fuel less dangerous than 20 kg of batteries?

Keep in mind that the big template doesn't have to go down to the bottom of the chassis and most drivers are not as wide as the template... so there naturally is free space besides the driver's hip.

Regards,
Thomas

[Crispy]

I wouldn't be too thrilled about having a fuel tank right next to me unless I knew that the required firewall was well designed. Perhaps the rule writers want additional structural protection of accumulators because of they believe they are more dangerous or more sensitive to structural damage.

It's hard to know what exactly the rules committee's intent is on every point, and there are lots of grey areas where everyone might not agree. I think this is one of those areas. Or maybe they will change it...