Aeromotor, yes this is Grassroots

Uprights are always heavy. Even the Miata pieces I am using on my locost are super heavy.

Thank you for the welcome, and for the nice comments you all wrote above as well! I would like to assure you that we highly appreciate all opinions and especially criticism given, as we believe this is the best way to improve our work.

JoeyM, with regards to the suggestion you gave, I have to say that it's up to the Aeromaster sports car company if they will open a build thread somewhere, as I'm just an external subcontractor to them doing the body and chassis design job. The build of the chassis itself is made in-house by the company, though. But when the next chassis is done I will post some photos here, and I think you all will like the upgrades on the chassis and suspension design.

AeroM wrote: Hello guys, I'm the chassis designer of Aeromaster LMP

Welcome! Glad to see you chime in and join us here. Overall the car looks very nice.

Uncapped tubes indicating poor node design (Suprising given some of the nice welds and tube joint work)

Obviously, those photos shown of the bare chassis are taken during early stage of the build. You can see that most tubes are temporarily welded with spots only to barely keep them in place, before final check of dimensions and applying of full welds. The chassis is designed with all caps on place.

I understand in progress. It would be superior to notch the tubes such that all sides of a square get terminated into another tube. This way all of the stresses get cleanly transferred to the other tube and the length of weld applied is higher and therefore lower stress. Example is a 90degree joint cutting 2 parts at a 45 is superior as the weld joint is X*sqrt(2) longer than if it was just two tubes of width X. It also minimizes the weight of the joint by removing some overlapping material. I do realize that this is a much more labor intensive and therefore costly manufacturing method and often is not necessary for the low stress parts. The US Exomotive chassis has eliminated some of this cost by laser cutting the tube joints.

Upper rear a-arm mounts horribly unsupported

There must be two X-braces bolted - above the engine and above the transmission, respectivelly. If you watch the video with my 3d chassis design here (http://www.youtube.com/watch?v=w0s21_V28B8) you will notice that at each side there is one hole next to the back rod end of the rear upper control arm, plus uncapped tube next to the front rod end of the upper control arm, leaved there to allow welding of mounting plate to connect together the two X-braces I mentioned above. This is easily recognizable at 2:30 min. of the video. Both X-braces are not shown on the video as at the time I designed the chassis it was still unclear which engine and transmission combo will be used on the running prototype, and these are added later "designed by eye" as I didn't had a referecen of the exact dimensions of the engine. Now that there is already PRV engine installed, and AUDI engine installation is in the works, all next chassis supplied to customers will have two types of X-braces properly designed in CAD, depending on which engine is chosen.

I see the holes in the CAD model and a properly designed Xbrace should reinforce the suspect areas. If the Toe-Link (3rd link controlling direction of travel) is going to remain as is I would strongly consider having the Xbrace tie into this area as well.

Rear Toe Link chassis side mounts mid tube and not in ideal location for bumpsteer (Ridiculous to have these anywhere but in a good location in the REAR!)

English is not my native language, but I think that "rear toe link" is probably what you call the 3rd link of the rear suspension that keeps the rear wheel in straight direction. If that's correct, then let me say that the square tube used there (30 x 30 x 2 mm) has much higher resistance to bending in this direction than a round tube with same diameter or weight. Probably you heard of the issues some Ariel Atom owners had with bent tubes after sudden acceleration, result of the use of round tube to mount the rear upper control arm. This will not happen on the aeromaster LMP due to two reasons: - Use of square tube. - Stress on that link is much lower than the stress taken by the two control arms.

I am not concerned that it won't be strong enough my concern is that the rigidity won't be such that the Toe will not change under dynamic loading. This toe change would happen somewhat unpredictably and may result in undesireable on limit handling. The number 1 job of a Chassis is to Rigidly fix the suspension geometry. I feel that loading into the middle of that tube without further support fails at that task. I would either try to reinforce that joint looking for a very high stiffness or redesign the rear suspension some to put that link on plane with the upper or lower a-arm. The angle may be such that it intersect the Instant center of the A-arms but you will get some minute amount of bumpsteer particularly with the lower a-arm inducing some amount of caster change due it being of a semi-trailing link design. It would be better to just put it inline with the A-arms and eliminate bumpsteer entirely while relying on the rigid nodes you need to create for the chassis side mounts.

Front lower control arm rear link chassis mount not a node, no reinforcement (This link takes MOST of the cornering force and Braking force)

The chassis is designed to use welded 2 mm thick steel sheets on the floor (5 mm below the upper side of the floor, separate small sheets between the floor tubes), and 1 mm thick sheets all around the cockpit area (again, separate small sheets between tubes). This pretty much makes the area next to the front lower control arm invulnerable even to extreme to braking forces.

Again the concern is more rigidity than absolute strength. I don't doubt that as designed it will be safe and function. The desire to put loads into nodes is driven by the fact that beams loaded in direct compression/tension can be MUCH smaller and lighter than those that are being used in bending the resulting structure would be much stiffer which is the #1 job of a chassis.

Main roll hoop no diagonal and no fore/aft reinforcement

The X-brace I designed was not used there by request to leave as mush space as possible inside the cabin as the company owner is tall and was worried that it will be too tight to fit inside. But after the car was assembled, it didn't took long to figure out there is plenty of room inside even for taller people, and so the X-brace will be used on all next chassis. It was not included in the running prototype as its body was already attached. The same refers to the X-brace on the roof, that's also not used in the first car. Personally I'm obsessed with doing everything extra strong, and you can see plenty of X-braces in the buggy chassis of Aeromaster sports cars, which is the company's secont project currently in development.

It is sad they have made that choice however I am encouraged that they will be re-considering the xbrace. The fore-aft bracing is absolutely necessary. This car will be capable of very high performance and a rollcage that meets competition standards should be included.

No tie in of side impact to roll structure

I'm afraid that I can't understand what is the thing you described. Could you draw a simple picture, please? I may be able to explain if I have a better idea of what we are talking about.

Sorry I don't have a picture. What I am saying is that the tubes designed to prevent side impact do not tie into the tube that represents the main roll hoop directly. They rely on additional joints to dissipate those forces. In a side impact the loads have to pass through additional joints to get to the main roll hoop protecting the driver.

Front roll hoop does not terminate in a Node

It's only 40 mm away from a very strong node where the tubes create 3 triangles. There is also a metal plate behind (not show on the video but used on the running prototype).

Roll hoop welded directly to the chassis rails without load spreading plates, gussets, or any kind of reinforcement at all

As the tubes are squre and renforced with separate small steel sheets in between (not large sheets next to the tubes), this all provides plenty of load capacity.

If properly welded this should be ok. The goal of the plates is to provide sufficient weld area to transfer the load. The roll tube is thick and usually the chassis steel is thinner. You put a say 4" weld around the tube and then use the thick plate to spread the load from that 4" weld to 8+" of weld in thinner tubes. In a large impact if the thick tube is welded to thin steel it can sear the weld in the thin material. The Chassis-Plate-Roll tube arrangement prevents this.

The front suspension geometry seems very strange with the lower links being very not parallel to the centerline of the car when viewed from above. They may have designed this in for a reason but it's hard to say.

The front control arms were designed this way due to three main reasons: - Cars don't roll along their longitudinal axis during high-speed cornering. Instead, they will roll diagonally, and so, it's better to use diagonal axis and inequal lenght for both front control arms. - This also redirects a large portion of the stress taken by the back rod end of the front lower control arm towards the lenght of its tube. - This control arm design follows the vedge-shaped body of the original Bentley Speed 8.

Sounds like this was done intentional so it will be interesting to see how it proves to work.

PS: By the way, there is an updated version of the chassis I design right now, called "Pro chassis". I mentioned it at the "About" text below my YouTube video. It will be slightly stronger, will come with X-brace above the engine designed to accommodate AUDI unit, and totally revised suspension able to take much higher loads.

Do you have an pictures of this chassis. It's reassuring to hear that you've been making some changes and progressing the design. It sounds like the design is a customer project for you so I can understand not having complete freedom to design how you want and playing by their rules. Good to see you engaging in some discussion and I hope that the car proves to be a success. As I said a lot of what is going on with the chassis/fabrication is very high quality work. It's just so often these kind of chassis are thrown together targeting lowest cost manufacturing with a good enough approach to design.

Good luck in the future with this and other projects.

 Well, the Aeromaster LMP Pro chassis is finally here. It was initially planned for a release a few years ago, but it took a lot of time to find proper CNC-laser pipe cutting machine, to make custom tooling for bending of the tubes at the required radii, to laser scan the transmission etc. The Pro chassis features a total redesign of the main structure and uses 45 mm diameter laser cut round tubes to comply with the FIA requirements. The CNC-milled aluminum uprights are available since 2017 and are fully compatible with the old chassis. However, the new Pro chassis has slightly modified A-arms with improved geometry, along with adjustable push-rod layout on all corners.

 The chassis built is done by preliminary assembly of the main sections on custom laser cut jigs to maintain accuracy and repeatability.

 Cheers,

 Bobi

I like the laser cut jig with the tongue and groove assembly.   I have access to a large laser table at work and am always looking for more ways to use it.

Joe Gearin said:

Joey M hit it on the head.

While we do welcome bargain fixes and love the $200x Challenge---- being cheap is not at the core of GRM.

If a guy has been reading GRM for 20 years and done well for himself and now he's tracking his Viper instead of his Civic--- is he less Grassroots? Hell NO!

We welcome all folks that share an interest in ingenuity and making the most out of what you have available. It just so happens that some folks have more available than others.

We (me) get a little touchy as we've had to reinforce this to potential advertisers who get the mistaken idea that our readers are cheap.

This just isn't true. Our readers buy a TON of stuff, and our advertisers do very well because of this. Sometimes perception is hard to break though.........so we try to nip it in the bud.

Thank you.

Seems like once the cost of a real transaxle (stands up to an LS engine without worry), LS, support stuff, dash, seats, wheels, tires, the kit, paint, it's getting into the realm of similar cars such as Superlitecars. I mean, it kinda has to, since so many of the parts are the same. The cost difference comes down to who built the chassis and where.

In reply to akylekoz :

Yeah, by using those jigs it's basically impossible to assemble the chassis sections in a wrong way, because every tube and plate is fixed to its proper position prior welding.

In reply to kb58 :

 The kit is much more complete than before and is a result of extensive upgrades in any department. The latest additions are optional custom made brake calipers and wheels. The wheels feature a cap that resembles a single central nut, though the mounting underneath is done by 5 regular nuts attached to a Corvette C5/C6 hub-bearing. The brake disc on the picture is an old donor part used for reverse-engineering and to test the assembly, so no wonder that it's a bit dirty. :) The CNC-milled aluminum uprights could be anodized in gold, black, silver and other colours. Mounting points for the pedals and cylinders are integrated into the chassis and the same strong plates also double as mounting points for the coil-overs of the front push-rod suspension. The cockpit of the chassis was widened and now can accommodate two persons. There are fibreglass interior panels that cover the chassis around the feet area.

In reply to AeroM :

Thanks for the updates! 7 years is quite a while!

I hereby dub thee the best zombie thread to date!

In reply to NOT A TA :

 Yeah, time files too quickly. :) During those years I wanted to reply in this topic and describe what the Pro chassis would offer eventually, but my simple belief is that it's always better to work hard and be able to show the actual product, instead of talking with bold promises for the future and show nothing. The Pro chassis was planned for a release several years ago (I mentioned it in the description under some of my YouTube videos from 2012-2013) as the 3d CAD model was in the works long time ago, however, making custom tooling for manufacturing required time and big investment. Meantime, a brand new warehouse was built for the future production. As I wrote in my previous post, the Aeromaster LMP kit now includes optional custom made wheels and brake calipers designed exclusively for the company. It's this kind of things that inevitably add to the development cost and time. Also, it took years to find a company with appropriate CNC-laser cutting machine to be able to produce the tubes at the target cost. That delay actually helped to source better components, some of which were reverse-engineered with laser scanning, so the final version of the chassis got even better and comes with accurate mounting points for many of the major components (transaxle, rack & pinion, pedals, liquid cylinders, wheels, brake calipers etc).

 CNC-bending machine is used to bend the pipes at the correct angle. Then, paper templates are used to cut either end of the tubes, and laser cut templates are used to verify the shape and size of the cut tubes before welding them to the chassis. The measured deviation around the bent areas is less than 0,5 mm.

Joe Gearin said:

GameboyRMH wrote: My grassroots-sense is tingling! It tells me that gearbox is far from grassroots-priced.

Sir, your "Grassroots-sense" is misguided. Grassroots does not = inexpensive

I know that is the party line now that the magazine has achieved a fair measure of financial success, but understand that a large portion of your readership doesn't really agree with that assessment.

Of course the magazine is the magazine and that is not ours to decide, but repeating it a lot doesn't necessarily make it true.

Robbie (Forum Supporter) said:

I hereby dub thee the best zombie thread to date!

Yes, totally. Glad to see this still happening. 

In reply to AeroM :

Wow, that is beautiful. 

In reply to Duke :

 Thanks! The building of the first Pro chassis is near completion, and I will show more pictures once it gets painted. Meantime, a real-size dummy toy model was created for a customer, so that it will be used as a way to teach kids how to change wheels. It sits in a custom simplified lightweight frame specially designed for this purpose. The majority of panel gaps were fully filled by customer request, with the engine cover remaining the only removable part. It also uses dummy wheels made out of fibreglass.

 The new custom made brake calipers and rims just got assembled together and await to be tested with the first built Aeromaster Pro chassis. The rims use Corvette C5/C6 hub-bearings with standard bolt pattern of 5x120,54 mm (5x4,75"), however they come with a cover that mimics a center lock nut to enhance the overall look of the car.

Wheels look great! I like the center lock look.

Who actually makes the brake calipers? Any details on the rest of the brake system?

In reply to NOT A TA :

 Hi, I'm glad to hear that you like the newly designed rims. They fit the car very well. Can't wait to get the engine installed in the new chassis to test it on a track in the summer.

 With regards to your question, the brake calipers are custom made for Aeromaster to our specification by a company in China that specializes in aftermarket upgrades, but I'm afraid that I'm not allowed to share full information. They are massive and bigger than the Willwood brake calipers and stock C5 calipers that we used in earlier cars. This is why we also had to design new custom rims to accommodate the new big brake calipers.
 
 Stock Corvette C5 rims may not fit the new Aeromaster brake calipers due to size constraints. However, Corvette C5 brake calipers and aftermarket Willwood brake calipers for C5 will still fit the the mounting points of the uprights, so there are 3 options for the brakes now, and 2 options for rims:

Aeromaster rims + Aeromaster brake calipers

Aeromaster rims + Corvette C5 brake calipers

Aeromaster rims + Willwood brake calipers for C5

Corvette C5 rims + Corvette C5 brake calipers

Corvette C5 wheels + Willwood brake calipers for C5

Test fitting of the main suspension components on the bare chassis. Can’t wait to see it painted in charcoal dark grey.

In reply to AeroM :

That's some nice TIG porn there.

Stampie said:

In reply to AeroM :

That's some nice TIG porn there.

I believe that it's a pulsed MIG welding, because the goal was to simultaneously reduce spatter, heat and stress, while also increase the weld penetration. :) The photos above show the bare chassis right after the welding. They are then processed with tools to remove any excess spatter and clean up the tubes.