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Old 05-27-2020, 07:16 AM   #1 (permalink)
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It's all about compromise - a study on front bumper design?

Many of you may have seen my new Off-Road Prius build that's in the works (if not there's a link in my signature).

One major component I would like to upgrade is the front bumper. Obviously the factory bumper is fairly good for aero and can be improved with a simple grille block and (more) flat floorpan, however it does not give the best approach angle for off road abuse nor is it strong enough for highway animal strikes.

This is where my study begins, how much compromise do I need to have to get my perfect bumper? Where are big advantages available in one area that detracts least from the other area?

The end product will most likely end up somewhere in the vast range between this:


And this:


And here's the car in its current guise:


Grill block and flat floor can both be combined with a metal bash plate which will likely extend all the way from the factory numberplate position all the way to the tail end of the diffuser, but other than that I'm open to front shape suggestions.

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Old 05-27-2020, 06:08 PM   #2 (permalink)
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Just to summarise what we've already communicated:

1. Height-adjustable air suspension will give you off-road clearance but also allow a good ride height for low drag on made roads.

2. Gaining a good approach angle would normally mean lifting the leading underside edge of the bumper. This is not good for drag or lift. As I think you said, best to have a removable section to change approach angle as required.

3. A full-length bash plate should be good for both low drag and off-road protection. But keep it wide and smooth.
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Old 05-28-2020, 12:36 AM   #3 (permalink)
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So maybe what you're willing to do is shape the reinforced bumper closer to the shape of the bow of a boat.
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Old 05-28-2020, 05:43 AM   #4 (permalink)
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Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
So maybe what you're willing to do is shape the reinforced bumper closer to the shape of the bow of a boat.
This is pretty much my current method of thinking, the flat section of floor will start as far back as possible for maximum clearance (the radiator support) and in front of that it will curve swiftly upwards to meet approximately where the numberplate currently is (about 250mm forward of the radiator, and 200mm above the flat floor)

This panel will act as a grill block (probably with movable louvres for Australian summer) and the front section of the bash plate, protecting the radiator. And could have a quick release front lip/air dam on the bottom of it.

The tricky part then comes on each side where the body curves around to meet the wheels, how much clearance will I need in front of each wheel vs how much air dam can I fit in front of each wheel?

If I remove the factory air intake box there is basically nothing outside of the chassis rails so I can bring the nose in quite narrow from the wheels to the radiator bash plate. There's also the possibility of cutting off the outer wings on the factory bumper and using them with some quick release clips to have removable air dams in front of each wheel?
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Old 05-28-2020, 05:47 AM   #5 (permalink)
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No one will be able to say what the results will be without testing of various iterations.

All else is just speculation - 'pissing in the wind', as we'd say here in Australia.
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Old 05-28-2020, 05:56 AM   #6 (permalink)
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Unfortunately I'm still waiting on an OBD2 reader to come from China and assist with "before" measurements, I'm quite interested to see what difference just taking the whole bumper completely off makes.
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Old 05-31-2020, 01:06 AM   #7 (permalink)
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Quote:
Originally Posted by bobo333 View Post
If I remove the factory air intake box there is basically nothing outside of the chassis rails so I can bring the nose in quite narrow from the wheels to the radiator bash plate.
Even though it may charge its toll on the aerodynamics, sounds like a good excuse to get a raised air intake which will increase fording ability.
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Old 05-31-2020, 03:39 AM   #8 (permalink)
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Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
Even though it may charge its toll on the aerodynamics, sounds like a good excuse to get a raised air intake which will increase fording ability.
I wonder how HV cables and fording go together?
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Old 05-31-2020, 08:58 AM   #9 (permalink)
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Quote:
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I wonder how HV cables and fording go together?
It's all well-sealed and insulated. As long as the HV battery stays dry, it'll be fine. But I can think of other reasons I'd avoid driving a Prius through a river!
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Old 05-31-2020, 11:32 PM   #10 (permalink)
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I can think of other reasons I'd avoid driving a Prius through a river!
I would also take it with a grain of salt, even though recently I got lurking about the fitment of a Prius-ish powerplant into some serious off-roader.

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