[snowdog]

Hello all,

I thought I would start a build thread. I have ordered a K1-attack kit car. I have started the assembly. My plan is to have a Tesla drive train. I am sourcing from EV-West. Hopefully that was a good company to partner with. I am waiting on batteries until the build is further along. I will definitely reach out to the forum for advice along the way. I am also documenting in YouTube. Feel free to follow along.

https://www.youtube.com/channel/UC-Uk13BnLTGAO5APsfuT9uw

 

[brian_]

If you are starting assembly, does that mean that you have worked out the placement and mounting of all of the EV components?

I've seen the advertising material on the kit manufacturer's website, but I didn't see any technical details. Do you have an illustration or clear description of the rear suspension? That's critical to fitting the Tesla drive unit in.

Update:
After some online research, I see that the kit uses the front suspension of the FWD donor at the rear, which is normal practice for mid-engine kits of this century. In this case, this means the double A-arm system of the donor Accord.

That's generally a good thing, but it is designed to fit around the conventional transverse placement of the engine, ahead of the axle line. In this case it seems to include the cross members from the Accord, to locate and mount the lower control arm and the steering rack (which is presumably replaced by fixed track rods). The rear cross member will probably go right through the bottom of the motor and inverter of a Tesla Model S or X drive unit (because they are behind the axle), although the Tesla front drive unit places the motor higher to clear the front of the battery case, which might help.

Your post in another forum says that you have motor mounting information from another builder; what's the plan to make the drive unit fit with the suspension and structure?

 

[brian_]

I normally don't watch anyone's YouTube videos, since they are black holes for time providing little if any value. I did watch the intro, hoping for an overview of the technical plan. Sadly, there is no plan provided... but a viewer's note: the music adds nothing and is louder than your voice. Turning the volume up enough to hear the words means getting blasted by the noise at the end. Does anyone listen to their own videos when they're done, or do they just toss them into the YouTube pile of junk?

Anyway... Nice garage.

 

[brian_]

I did look through (no audio, 2X speed, skipping ahead) the front suspension video. Combined with some forum reading, I see that the bits are a VW/Audi McPherson strut system converted to double A-arms. This type of conversion is relatively common for this sort of car, although it seems like a strange choice for a car using Honda components at the rear, since there are stock double A-arm Honda front suspensions... they are using the one from the Accord at the rear.

More importantly, despite using rocker arms to place the spring/shock units roughly horizontal across the top, it looks like they still managed to occupy the space behind the axle line which could be a nice battery pack space with frame tubing.

Do you expect to be able to put any of the battery up front?

 

[snowdog]

Brian, thanks for all the kind words . My first YouTube attempt ever. Obviously I have a lot to learn.

I obtained the frame dimensions from the kit manufacturer. I sourced the Tesla dimensions from GrabCad. It will fit. Obviously I will need to modify the frame to meet up with Tesla subrame and I may need to modify the suspension points. I may need to widen the rear fenders depending on what size tires/rims I end up going with. I am waiting on the battery purchase for now as it will take me some time to assemble the car. I am planning on ~30kW. Batteries can fit up front as well as between seats and behind the seats. Much of the other electrical, contactors, DC-DC converter, Tesla controller, etc. will be in the back.

 

[snowdog]

Also, maybe I wasn't clear. I will be sourcing the entire tesla subframe (control arms in all). I just need to mate it with the frame.

 

[MattsAwesomeStuff]

I did look through (no audio, 2X speed, skipping ahead)

Just FYI, I installed "Video Speed Controller" add-on. It lets you speed up videos as much as you want (unlike Youtube that maxes at 2x and requires you to click several times to do it), though the audio dies above 4x.

Also it has hotkeys so you can adjust speed on the fly. S for slower, D for faster. Bumps it up 33% each time.

I can't live without it on Youtube. After a year, almost everything gets watched at 2x minimum, and if they speak clearly, 3-4x. If there's no narration, just music or audio (like a lot of restoration videos have), I'm at 4x minimum. Surprisingly, a 1 hour unnarrated video crushed into 15 minutes is almost tolerable.

 

[snowdog]

Also, maybe I wasn't clear. I will be sourcing the entire tesla subframe (control arms in all). I just need to mate it with the frame.

 

[brian_]

Brian, thanks for all the kind words . My first YouTube attempt ever. Obviously I have a lot to learn.

Please don't take the YouTube comments personally - almost nothing in YouTube from anyone is worth the viewer's time, and I'm far from the only person who feels that way. Lots of people have posted dozens of videos, and have never produced anything worth the time it takes to watch. In most cases, a couple paragraphs of text and a few still images would be more informative. If it must be video, then just leaving out background music would help.

 

[brian_]

I obtained the frame dimensions from the kit manufacturer. I sourced the Tesla dimensions from GrabCad. It will fit.
...
I am waiting on the battery purchase for now as it will take me some time to assemble the car. I am planning on ~30kW. Batteries can fit up front as well as between seats and behind the seats. Much of the other electrical, contactors, DC-DC converter, Tesla controller, etc. will be in the back.

It sounds like you're well along in planning. I think I understand the general intent and approach, although it sounds like Tesla components were the only option considered; was that because a ready-to-run product is required, and EV West and others promise that with Tesla drive units?

I assume that you meant 30 kWh (not kW). That's not much capacity for a high-powered application, so range (assuming aggressive driving, given the nature of the vehicle) will be short. It is difficult fit in more in a car not designed to accommodate battery volume.

I'm impressed that the kit manufacturer provided frame dimensions. That's helpful. I see that their order options include "electric drive"; I assume that just means that (compared to their Honda and Toyota options) they just omit the fuel tank, cooling system, and shift linkage. Since the others are set up to bolt in suspension parts from the donor, and there is presumably no donor for the electric drive, does it just have plain frame tubes with no mounting points for any suspension?

 

[brian_]

Obviously I will need to modify the frame to meet up with Tesla subrame and I may need to modify the suspension points. I may need to widen the rear fenders depending on what size tires/rims I end up going with.

Also, maybe I wasn't clear. I will be sourcing the entire tesla subframe (control arms in all). I just need to mate it with the frame.

I wondered when you mentioned the Tesla subframe earlier if you were planning on using it, complete with the whole Tesla suspension (like Chris Hazell's drift car project - see Tesla Powered Nissan r32 skyline). That can make sense and avoids several compatibility issues, but it will involve substantial frame modification and will result in a very wide car. Chris discussed the details of the width issue; fortunately, the K1 Attack body is designed to fit over an Accord front end which is a little wider than the Skyline, so the additional fender width won't be as extreme.

Keep in mind that to "just mate it with the frame" is not trivial, since the frame needs to support and locate the subframe at four specific points (relatively low in the vehicle), plus the rear suspension spring and shock struts (relatively high in the vehicle). The subframe will pull down on the frame at the four mounts (with the weight of the subframe and drive unit), while the struts will push up on the frame with the entire weight of the rear of the vehicle.

This is a reminder that the Tesla "skateboard" idea is nonsense: the car is a conventional unibody (the tube frame will take the place of that in this case) with front and rear subframes that support nothing but themselves, and a battery in between which supports nothing but itself.

I suggest taking suspension modification seriously. Pickup points can't just be moved without consequences, and most people in this forum don't seem to realize that. On the other hand, if you use the complete subframe with suspension, I don't know why you would need to modify the Tesla suspension (other than changing to softer springs and shocks for the lighter vehicle); the Honda (or Toyota) suspension likely would require modification.

 

[snowdog]

Brian, you make many good observations. Several electric powered options were considered. I was not keen on options that would require clutch and shifting. I also liked the available power for the small size and weight. I know there were other options, however this is the one that I landed on. I am not planning to change the tesla suspension the only modification that may be required is where the shocks are mounted to the frame. The K1 is quite wide, as most cars use wheel spacers when used with the honda drive trains.

 

[remy_martian]

IMO, the Tesla strut suspension sucks. As Brian points out, the load point is way high. It'll be interesting to see if and how they ditch this with Roadster II, and even the pickup truck (if it actually is a truck vs an electrified Honda Ridgeline).

Why have the Tesla subframe at all -- seems to me like it's a lot easier to just mount the drive unit itself (IIRC Damian, a <gasp> Youtuber, did that with his BMW), and run your axles to something with a more sane and/or conventional geometry?

 

[Duncan]

IMO, the Tesla strut suspension sucks.

Any reason for that comment? - Strut suspension works incredibly well which is why 99% of cars use it

 

[remy_martian]

I'm old school Jaguar vs BMW/Audi knockoff.

Seems there's one German suspension designer that keeps getting himself fired, and is making the rounds -- latest stop, Tesla.

Take a look at the "lightning rods" in the Tesla skateboard pics. Ridiculous, IMO. Makes a low slung sportscar derivative next to impossible because you have to look through the strut towers.

Done right, the top of the springs is no taller than the outboard brake rotors would be...

Tuck a Tesla drive unit into an XKE rear suspension assembly and you have the makings of a sportscar.

I'm not tickled by the bazillion rubber bushings and no parallel link on the Tesla rear knuckle to keep it where it needs to stay in free space. Rube Goldberg and it's no wonder it clunks.

EDIT: finally at the computer and looked up a K-1. A cutie worth adding to my never-get-done project queue. It's gunna look funny with Tesla struts poking up through the rear quarters, lol.

 

[remy_martian]

I obtained the frame dimensions from the kit manufacturer. I sourced the Tesla dimensions from GrabCad. It will fit.

I'd want a CAD model of the frame vs measurements. This one's a case of cut once, order a new frame from Eastern Europe if you F it up.

It also sounds like they have the means to mod the frame as needed -- why not have them do the Tesla drive unit mounts and fitting vs bodging a bodge? I'd even have them mod the chassis to accommodate a floor pack between rocker tubes. It's not like they couldn't sell a bunch of these for their initial investment of effort...

 

[Duncan]

The height of the strut tops is a pain on the front of my device - on the back? - simply not an issue and that is only because of the "Lotus 7" type look - on any normal car the strut tops are simply not a problem

Have you ever done anything with an XKE rear suspension setup? - I mean it's cutting edge technology 70 years ago! - I like my driveshafts to drive the rear wheels and NOT have to resist suspension and brake loads as well

 

[x.l.r.8]

To be fair from hot rods to drag racers it does do it well, increases the unsprung weight and is highly adjustable, easily modifiable and pretty damn strong, is way better than a fixed axle and had LSD’s in most of the cars with wide final drive ratios. For a track car I’ll take a jag IRS over a 9 inch.

 

[remy_martian]

^^ "Brake loads"?

Regen, son.

Regen.

The inboard brake, 70 years later.

lol

 

[brian_]

Strut suspension works incredibly well which is why 99% of cars use it

The spring/shock "struts" are not part of the Tesla suspension geometry at all. The spring is just packaged on the shock. When people refer to "strut suspension" as a type, they normally mean McPherson strut designs, in which the strut controls the caster and camber. However,

• while McPherson struts are the most common front suspension design, particularly in front-wheel-drive cars, they are not in 90% of all front suspensions
• McPherson struts are now (in this century) rarely used in rear suspensions (although the MR2-based version of this kit uses them because it gets them from the donor)
• neither front nor rear of any Tesla model uses McPherson strut suspension