CURT16 Building Process

[Ahmad Rezq]

This year i would like to post the building process of our second car in Cairo Uni FSAE team. i want to go forward to the core of the topic without typing too much as an intro, but what i would like to say that: i'am sure that in this topic our team will gain many things.

This year we modify 2015 car with the main goals of:
- Building a car complies with the rules(seems stupid, every team should do so) but unfortunately we didn't join the dynamic events last competition :( .
- Finishing the car 4 month prior to the competition date (This year we are planing to join UK competition)
- We don't have high goals regarding the dynamic events. joining the dynamic event with the main goal to finish the endurance is perfect for the team. But we do have some goals on the static events.

Moving to every single system (Our goals regarding this system, and what we have finished so far).

The power train:
- Engine: in 2015 we have used KTM 450 EXC engine we do not have any plan to change it this year.
- The intake system: this year some modification regarding to the material of the intake system and its integration on the car.
- The exhaust system: Some modifications related to it's packing in the car.
- The radiator: we will design another radiator with the main goal to finish the endurance.
- The fuel system: we are still using the motorbike pump and we will modify the fuel tank.
- For the differential and for financial reasons we will use Torsen differential, with some modification on its fixation.

The suspension
- Last year we have spent a lot of time on the suspension kinematics. but we ended with a complex suspension with some errors in the manufacturing and many deviations from the designed points. although we are working to increase the team understanding level of the suspension. but with the main target to finish the car very early we will do it simple, no time to spend to optimize the dynamics, no anti features , direct acting . . . if i want to set the suspension goals this year:
1 - A simple suspension (Less time in designing and manufacturing)
2 - well mechanical designed wheel assembly.

- Although Mr Pat has advised us to use 13" wheels, but we do have 2 sets of tires + rims that are ready to be used. so this year we will go for 10" wheels.

The brakes
- We went very fine in braking system last year (we have some braking testing) this year we are planing to go for angled M/C pedal box (Decision matrix).
- last yea we faced some problems in the brakes lines as we used local lines but this year we are planing to buy them from an international supplier.

The chassis.
- Unfortunately the main reason for not joining the dynamic events in FSG15 was the chassis , so we will focus more on the chassis rules.
- Simple and minimum required tubes chassis is considered enough (Removing extra tubes, planar tubes, easy to be jigged during the welding process)
- In Egypt we don't have the minimum required tubes stated in FSAE rules we have thicker and larger tubes. this year we want to deal with an international supplier to supply for our chassis tube (It's not a final decision) but this will reduce the chassis weight 20 kGs :D (As if you designed based on the minimum available tubes size in Egypt you will be lucky to end with a 50Kgs chassis).

- The electric team
we have switched from using the stock KTM ECU to megasquirt, so the team is now working with the engine team to run the engine .
we want to do the minimum requirements from the competition regarding the electric system although we have received some negative feedbacks from the design judges in FSG15 as we have to use more sensors. but i think this year a running car 4 month before the competition is our main priority.

In the next comments i will add what we have finished in the car CAD model.

[Ahmad Rezq]

Some Photos from the Chassis Design.

733734735736737

[Ahmad Rezq]

We are planing to machine the suspension brackets and bolt them to square tubes in the chassis. But we are still analyzing the decision.
Also as shown in the picture we will machine our rod end spacers.

[Adam Farabaugh]

Here's a suggestion if you want to decrease complexity and eliminate a major mechanical design fault: no rod ends in A-arms. Unless you have 5 independent link suspension there's no way to use them to make adjustments without introducing bending stress into the parts. Plus, it's lighter!

Other list of suggestions:
- why use bolted suspension brackets? waste of time, just waterjet some steel tabs and weld them on
- why is the driver so far away from the engine? subtract that ~6" of chassis and save even more money and weight
- your engine mount points are complete untriangulated
- why is the front of the chassis so damn large? I see this a lot in developing teams, never can understand why the front bulkhead is so high. Just make the frontmost bulkhead the same size as the standard IA, no larger.
- are you really using .5" od tubing for suspension arms? What wall thickness? rear a-arms look buckling prone to me, what is target car weight?
- rear toe base is hilariously small, can you say "terminal toe compliance"
- In addition the rear toe link is putting serious bending loads into the a-arm tube that it's mounted too. This could work in the sense that it won't break, but again looks like you're using very small OD tubing...
- I seriously doubt you need that much space behind the chassis for the differential, just move the entire sprung assembly backwards relative to the wheels
- rear bulkhead is untriangulated, use some of your .5" OD tubing to stiffen it up maybe. Or get rid of the 3-part upper member with 45-degree welded joints? seems to serve no purpose
- side-view triangulation is pretty complete, top view not so much (thank you SES for only caring about side view)

[Ahmad Rezq]

Hello Adm, Thank you for your notes. I got your all points.

- I'am about reduce the rear zone to save some weight (so completely agree with that point).
- For the front zone height: I'am sure you went trough this process ( The Percy rule + the templates + steering column + steering wheel) all together defines the front zone.
- 15 mm the outer diameter (yes in the shown pictures they are smaller but things they are updated now) of the suspension links (In Egypt market we have narrow options).
- I'am planing to increase the toe base in the rear suspension (Totally agree with you).
- (Edit) Target weight 180 kgs with +20 kgs acceptance (some lap simulations were done on optimum lap).
- some members are added to the floors.

[Jonny Rochester]

Some short comments:
I agree that rear-toe compliance would be bad. Increase the toe-base on the rear upright, and rethink the wishbone angles.

Your firewall will need to come further forward, inline with your seat back. As for normal packaging, your fuel tank and battery and exhaust pipe would all be forward of the engine, but behind the firewall.

Looking at your Percy template, it seams the driver sits very upright. That's fine if that's what you want, it creates good visibility, and possibly low yaw for turning. For our car I have chosen a much more reclined seat angle, of about 40 degrees to horizontal. This is for lower center-of-gravity, with a small trade-off in visibility.

[Z]

Ahmad,

Very good that you are doing this build-log. There are many, many benefits for your Team. I know you know this, because you have seen the results on Jonny's and Christian's (Aston Uni) similar threads.

Most important at this early stage is that you keep all your thinking very fluid.

DO NOT LOCK-IN ANY DETAILS OF THE DESIGN!

So, do not put too much "value" on your current frame designs. Best to print out your above design, then DELETE the file on computer. Then do another dozen+++ similar quick-and-dirty layouts. Print on paper, and delete on computer. Or, better yet, just hand-sketch on paper.

Then, after a week or two of all the different frame designs swirling around in your head, get the Team together to have a critical review session of all those different ideas, as they appear "roughly sketched on paper".

Perhaps someone will suggest that Design-1 (ie. the one above) "...seems to have an unnecessarily large ground clearance of about 120 mm, which, err..., raises the whole car's CG too high?!!!". And other such useful comments (such as Adam's and Jonny's above).

So you can tear-up that first sketch, and focus on the many other rough layouts you have...

Repeat: Keep everything flexible now, so you can gradually home-in on a reasonably good design.

Z

[Mitchell]

Ahmad,

What is the reason for selecting that longitudinal position for the rear bulkhead?
How much clearance do you think the driveshafts need to the chassis?
How much angle can you run on your tripod joints?

Please completely revise your rear toe control... even if it adds many kg. Rear toe compliance will destroy your chances of driving fast, a few extra kg will not.

[Jonny Rochester]

For the rear toe compliance issue, I think the most normal thing to do would be to move the lower upright mounting point forward. The rear upright mounting points don't need to be inline with the axle, so spread the 2 lower points out either side of the axle.

[Ahmad Rezq]

Jonny Rochester
Thank you for your notes. For the firewall a lot of modification after completing the car assembly with the engine parts.
For the toe control I moved the rear control arm mount on the upright 30 mm to the right and the tie rod 30 mm to the left. Now the normal distance between the tie rod and the line connects the 2 control arms mounting point is 51 mm now.

Z
I do agree with you Erik in doing dozen of designs and modification as long as the team will follow the time of the design phase. and in this post 2nd trial with some modifications is attached.

Mitchell


What is the reason for selecting that longitudinal position for the rear bulkhead?
How much clearance do you think the driveshafts need to the chassis?
How much angle can you run on your tripod joints?

- Actually the rear area was built with the main targets to ( 1- increase the engine area as we faced many troubles during the assembly of 2015 car , 2- No rear box design. 3 - supporting the control arms on the rear area corners) some Cms were added to the 2015 chassis design and i do agree it's very large)

- In the shafts clearance : IMO the clearance that neither the sprocket nor the shafts hit the chassis tubes during their operation.

- We are using Tripods and shafts from RCV, if i do remember very well i think about 12 degrees
------------------------------------------------------------------------------------------------------------------
In the 2nd trial
- the rear zone was minimized ( some inches were added to the cockpit )
- The side impact area were redesigned to reduce the driver height from the ground to lower the CG and the nearest member to the ground is around 4 cm
- Regarding the toe control as I've mentioned earlier I moved the rear control arm mount on the upright 30 mm to the right and the tie rod 30 mm to the left. Now the normal distance between the tie rod and the line connects the 2 control arms mounting point is 51 mm.
((SOME TUBES WILL BE ADDED TO THE FLOOR))

I'am working on reducing the height of the bulkhead and also reducing the engine CG height.

[Z]

Ahmad,

Better, but still many iterations to go...

I would be doing these first "rough draft" sketches by hand on square-graph-paper at a scale of 10:1. So, with paper that has 1 cm squares, the wheelbase is about 16 squares long (= 16 cm on sketch, 1.6 metres full size), Percy's legs are ~9 squares long, etc. Draw three views, namely side-view (as second image above), plan-view, and end-view, with all three on a single A4 sheet of paper (plan- and end-views only need to show half-car on one side of centreline).

This scale gives more than enough accuracy for this stage of the design process.

Some quick comments for the next iteration.

1. Lower the engine so it is ~4cm off ground (same as driver's seat).

2. The above allows the engine to move forward ~10 cm (leave just enough room for exhaust pipe, but NOT TOO MUCH unnecessary space).

3. The above allows all wheels to move forward ~10 cm relative to the rest of car, for better overall weight distribution.

4. Top of Front-Bulkhead only needs to be about as high as top of wheels. FB should be MINIMUM LEGAL WIDTH (ie. make same width as standard IA or bit less). A FB ~35 cm wide outside (30 cm inside) is more than enough (= enough space for feet).

5. !!! IMPORTANT !!! Rear toe-base MUST BE INCREASED !!! I would aim for ~15 cm (ie. 150 mm, not 51 mm). This is quite feasible to do (hint: move bottom BJs on upright UP a few cms, then wider apart until their brackets are ~1 cm away from the wheel-shell).

A dozen or more of these rough sketches now will save you a mountain of work (and grief!) later on.

Z

[Jay Lawrence]

To add to the above: the picture of your rear unsprung shows your lower inboard 5th link putting a REIB. For me, the best way to fix this is to have a Z-arm rather than a 5th link. If not, then make it so your 5th link goes to its own node.

[Ahmad Rezq]

Didn't Check Z and Jay Comments yet ( After attaching the photo i will read them and comment in the same post)

- I have reduced the Front Bulk area (trapezoidal shape 435mm, 320mm the two bases, 370 height) why not make it square, actually i was trying to make the front zone side tubes in same plane (except the lower tubes).

- The engine is now lower for around 40mm compared to the previous position.
- The red arrow (1) is the rules template (Re-checking the template with the rack).
- The 4 black dots in the rear are the suspension pickup points on the chassis ( All are fine except that one of them is not mounted on a node).
----------------------------------------------------------------
Z
-I will buy some square graph sheets today and try to sketch on them, Although it seems a little bit exhausting process to modify the trials on SolidWorks, Adding the Tubes and so on, but I think i will be quicker on SolidWorks than paper sketches.
- Before reading your comment i was finishing the modification to the last trial, I will work on lowering the engine more.
- Some works will be done trying to increase more the toe base.

Jay
You mean like this ?
https://www.facebook.com/BlueStreamline/photos/pb.106171376071650.-2207520000.1442236246./932659870089459/?type=3&theater

Edit (Another attachment was uploaded)
743

[Mitchell]

From that last iteration just move all wheels forward at least 75mm (or chassis back 75mm...) There is no reason your rear bulkhead plane can't be ~20-30mm forward of your rear axle CL plane.

This will also improve your rear toe control as you will have less forward angle on your links

[Z]

Ahmad,

One of the main goals of these initial concept sketches is to see all the big-picture parts, and, most importantly, all their inter-relationships. So, here you want to show driver+pedals, engine, 4 x wheels, major frame parts (roll-hoops, bulkheads, SIS), and perhaps vague outline of suspension and bodywork, all together on the same page.

The 3-view drawings (all on same page) work best for this when some degree of dimensioning is required. At this stage the dimensions (ie. lengths of parts, etc) only have to be accurate to a few centimetres, so "rough hand sketches" are good enough. Incidentally, perspective or isometric drawings are good when dealing with very general concepts, such as the "topology" of a mechanism, but not so good when you want to keep track of the relative dimensions of the parts.
~o0o~

Back to your design. It seems that you have decided that your Double-Wishbone suspension should have parallel and horizontal arms in end-view. This arbitrary decision is now ADVERSELY affecting your frame design. This is a MISTAKE.

As you may already know, I do not see any significant benefits in DW suspensions. However, I do accept that many FS students find it is easier to go that way. But you should know that there are a great many ways of getting DWs wrong, and a much smaller number of ways of getting them (passably) right. The big problem is that a bad DW design can then lead to an even worse frame design.

With above in mind, here are two good big-picture goals for overall design.

1. Flat floor, from front-to-rearmost points. This makes jigging much easier (just clamp bottom frame tubes to a flat table) and it puts a lot of mass at the lowest possible position.

2. Hang front-suspension off Front-Bulkhead. On most FS-cars the structurally very strong and heavy FB, with its mandatory welded-in 1.6 mm plate for IA, is too far forward, which gives too high Yaw-Inertia and too much F%. More relevantly here, the very strong FB is completely wasted as a "structure".
~o0o~

So, I suggest you think about a frame with a flat floor, ~4 cm above ground, for full length of frame.

Attach the lower-wishbones (F&R) to the frame close to this flat floor, say about 5 to 10 cm above ground. This means the wishbones slope down-to-centre, which is OK! But upper-wishbones must slope down-to-centre even more, so in end-view the upper and lower-wishbone n-lines intersect near ground level (= ~horizontal wheelprint n-lines = OK). Steering-rack also moves down with floor. So the top-tubes of the footbox area also drop down. Win, win, win!

Next, think about moving all wheels forward another 10 cm. Rear driveshafts may have to sweep forward (from-diff-to-wheels). This allows you to have the front-wishbones attach to the Front-Bulkhead. The whole footbox structure becomes much simpler...

I have already done several such sketches on post-it notes. There are many ways to fit it all together quite neatly! :)

Z

[Jay Lawrence]

Ahmad,

The pictures in that link are pretty much what I meant, but the toe base is way too small and also I would use an encapsulated spherical bearing because it's stronger and neater and you don't need adjustment (i.e. rod ends) on both ends of the arm.

[Ahmad Rezq]

Mitchell,
I have moved the two wheels forward, now the longitudinal distance between the rear wheel center to the Rear BH is zero.

Z,
- in the attached sketch: Flat floor 5cm off the ground.
- The lower Arm pickup points are 10 cm off the ground.
- The upper Arm pickup points are 23 cm off the ground.
- the wheels are moved forward as mentioned earlier.
- The front hoop is now 5 cm lower than the previous trial.
- The cockpit is increased about 5 cm.
- The upper side Impact member is now higher and a member was added to connect the Main hoop bracing supports to the upper side impact
- Didn't reach the distance yet to support the Front Arms Pickup points to the FBH (Didn't play with the control arms points except the modification suggested by Z).
- The Control arms are shown in the sketch, The (X) marks are for the dampers pickup points on the chassis
- The big challenge IMO is the dampers Mountings to the chassis. (As I have mentioned before we will go for direct acting suspension, we already have our dampers which are 250mm distance from both spherical joints center).

------------------------------------------------
I'am also attaching the front wheel assembly of the 2015 car for receiving criticizing
- Live spindle Design.
- two DGBB 6008-2RS1 (For 40 mm Diameter 6008-2RS1 is the only available bearing in Egypt Market).
- A shoulder in the upright to support the outer race, Shoulder on the spindle and a nut to support the inner race.
- Fixed rotor design (We faced some problems after manufacturing in the rotor clearance with the calipers but some washers solved the problem)
- IMO the angled brackets for Control Arms inner mountings wasn't a good decision (Although we had a sponsor who has the facilities to manufacture them) but it costed us a lot of time. I think wide non angled brackets with some spherical joints spacers are fine.
-----------------------------------------------
Jay,
I will give the Z-arm design a try and post it here.

[Freddie]

Just to build on Z's emphasize on sketches: I recommend building either small scale or even full scale models of the car, even a full scale model of an FSAE car isn't going to take up that much space. Our team did this for the first time for the 2015 car, with PVC tubing (some mistakes in planning even had us make do with 30mm instead of 1" tubing but it served well at that point) and stuff such as the engine and electrical boxes built out of floor insulation foam (the university gets the stuff for free from the factory that makes the foam blocks). Panels or plates can easily be made out of cardboard or thin plastic sheets. It took maybe one and a half day to make it, but that time was well worth it and it also served as an activity where people with vastly different responsibilities started talking to each other. I still believe that this, along with some other things that were done on the non-technical side of the project, was instrumental in the car running under its own power in April instead of July (usually the weekend before FSUK, at best).

[Ahmad Rezq]

Freddie,
In 2015 Car we had built a model for our frame using 1" PVC tubes, it was helpful to check the chassis rules, I think it will be a good idea to do the same this year with adding some foams.

[Jay Lawrence]

Looking good Ahmad.

Just a note on the bearings: it is generally good practice to use a spacer through the centre, so that you have something to press the bearings up against when installing them. Also, I'm not sure of your packaging constraints but to me that centre spacing on the bearings is quite small (magnifying any tolerance issues you might have, plus those of the bearings).

[Z]

Ahmad,

Some quick notes

1. As suggested by Freddie, it is very useful in FS to build a full-scale mock-up of the car. This gives you a much better idea than you will ever get from CAD of the relative importance of different parts. Christian's similar "Aston-Uni-build-blog" from a ~year ago progressed much faster when they started sticking tape-lines on the floor and building a cardboard mock-up of their car. (Sadly, their Supervisor's scuppering of all their good work a few months later meant they were a complete failure at FSUK-15. :()

2. Your suspension arms DO NOT have to attach directly to frame-nodes. When you design the car full-scale as above, you soon realise that "missing" a node by a few centimetres is no big problem. The key issue here is how well you design the many little brackets and gussets that carry the loads. A node near the middle of a large FLAT side of a footbox has no more strength or stiffness in the LATERAL direction than does the middle of a straight length of tubing. Good frame design is about distributing the forces efficiently. Just "joining up the dots", FS-style, does not guarantee this.

3. Further to Jay's comments ... your wheel-bearing design is VERY BAD! (Sadly, very typical of FS/FSAE.) The 6008 DGBBs themselves are adequate, but you should move them further apart. Try a ~40 mm gap, rather than your current ~10 mm. And, very importantly (!), there should be a spacer between the inner-races of the two bearings that is clamped very tightly by the big nut on the end of the axle. And better to use a 40 mm diameter locknut, available from most bearing suppliers, to do that clamping. And the inner-races should be a reasonably tight push/press-fit on that axle, to stop them "walking" around it. These are the most basic "bearing design rules" that your teachers should be teaching you.

Otherwise, keep iterating...

Z

[Tim.Wright]

One thing on the bearings. Based on what I saw in tech inspection at fsae Italy last weekend, it seems most teams are not correctly preloading the bearings properly and this results in a lot of free play at the wheel and durability problems. Some cars were so sloppy I was able to move the wheel +\-1deg with my hand. This was at the extreme end but I'd estimate at least half the cars I checked had free play in their spindle bearings.

This is shit for 2 reasons;
1. This free play manifests itself as a binary toe and camber change. As soon as the tyre load changes sign, so will the free play and hence your toe and camber angles. Its not a linear, progressive change like you get from compliance, but an abrubt step change which has the potential to make the car very difficult to drive. Its also undamped so there's the possibility that it can also result in grip killing vibrations.

2. Preloading the bearing means that any external loads are shared by all of the balls or rollers in the bearing. On the other hand, if there is free play, it means that some of the balls are not in contact with the race and therefore cannot transmit any load. The result is that only a fraction of the total number of balls are transmitting the load so their average contact forces are higher. This will obviously result in early failure.

So I guess the moral is, if you are going to spend a lot of time optimising your kinematic curves, make sure you install your bearings properly otherwise the wheel will end up just pointing where it wants

[Ahmad Rezq]

First I'am Attaching the photos in 2 posts and in the 3rd one i will go through Jay,Erik and Tim comments + Points on the attached photos

755756757758759

[Ahmad Rezq]

Rest of photos,

[Ahmad Rezq]

- I received the points on bearing from you Jay,Erik and Tim. I will upload the wheel assembly design after few days.
Erik,
This week we will build a PVC chassis model + Tires some foams and so on. I will post some photos next week for the model.
------------------------------------
Points on my uploaded photos to receive criticizing:
1- I went in depth for the last trial i modified the front suspension and attach the control arms points on the FBH, In the footbox zone i added the tubes mentioned in the rules + 3X1mm steel plates (Floor+2 sides), The damper front pickup point I have 3 scenario (a- To feed it some mm above the upper Arm pickup point on the front hoop. b- to feed it in the diagonal FBH support tube. c- to feed it directly to the 1mm steel blate maybe welding or bolt brackets.

2- The suspension pickup points brackets to the chassis, in this trial a 2mm steel bracket (Laser cutting), well be welded to the chassis. In FSG 2015 Our suspension brackets failed in the technical inspection for the reason of (Not complete circumference welding, But it was impossible for us to weld through the gap between the brackets as there was no room for the TIG torch.

3- For the steering column + fixation as shown in the photo, I didn't use any gears or U joints just a direct column from the steering wheel to the rack. Last year we used a double U joints for a 128 fiat car it was welded to each other with no way to support the steering column properly. for the fixation as shown, + A bearing will be pressed.

4- control arm brackets on the upright. Horizontal bracket for the lower arm + some spacers and 20 degrees inclined bracket for the upper arm. for the control arm design, 2 tubes 3rd tube which contains the bearing.

5- Damper bracket on the control arm 3mm laser cut brackets.
------------------------------------------------------------------------------
Important discussion i want to share:
After one year of experience dealing with the Egyptian sponsors and the manufacturing process. It's terrible, Last year although we had a deal with the sponsor in January we received the money 3 month later. We received many parts from the manufacturer 3 month later, Yes it happens in every place in FSAE projects. anyway we set a preliminary plan to start the manufacturing process of some parts after 1 month, (Chassis, Wheel assembly). it may affect our design process, as far as we iterate the designs, better results will be obtained, but it's not ensured in Egypt as we do expect many time shift (3 month based on last year work).

[Z]

Ahmad,

You are getting closer, but still some way to go...

Also, while all these suggestions might sound like never-ending NEGATIVITY, they will actually make things easier for you in the long run. :)

Better to get rid of the mistakes while they are just sketches on post-it notes (or digital equivalent), than to discover just before comp that it doesn't work. Aaarghh!

So...

1. WHEEL-BEARINGS - I agree with everything Tim said. Especially that this crucial area is so often badly done in FS. To repeat earlier suggestion, the 2 x 6008 DGBBs, with separation ~40 mm, is OK (in fact, better than many other FS designs). But the build tolerances (eg. "preload") are important to get right.

What material are you making the axles from? Steel (yes!) or aluminium (aaak!)?

If good quality steel (~4140+), then you can drill a 20 - 30 mm diameter hole through the axle for "added lightness" (leave thicker wall where higher loads). If aluminium, then drill a smaller hole, and use a M16 x 1.5 bolt (8.8+), full-length of axle, to clamp the bearings together. Relative difference in width of inner-race-spacer and outer-race-shoulder sets the "preload" (inner should be narrower).
~o0o~

2. ERGONOMICS - I am not sure what the average H. Sapiens body-shape is in Egypt (it varies a lot around the planet), but your "Update 1" side-view pics above tell me you will need an Orangutan to drive that car (ie. very long arms!).

It is these sorts of issues that are most easily found and fixed by building a full-scale "Ergo-rig". Start with a thick plywood base, then add more plywood, cardboard, PVC pipes, whatever, to build up the footbox, sides, seat, etc. Most importantly, it should be something you can actually sit it, and pretend you are driving the car (eg. check elbow-room while turning steering-wheel!).

I think a gap between the two roll-hoops of about 0.8 metre is about right. So move FRH ~0.1 m rearward. Then move the steering-wheel about 0.2 m rearward, but check this when sitting in the ergo-rig. The "no-UJ" steering shaft is good. The more vertical plane of the more rearward steering-wheel should be more comfortable.
~o0o~

3. FRAME-STRUCTURE - Based on the still rough, conceptual, design so far (in side-view), one thing I might aim for is an upper-SIS-tube that runs horizontally for the full length of the car. So its top-surface is at the mandated 350 mm above ground, all the way from front-to-rear. I would make this THE MAJOR structural member of the frame. As such, it could be increased significantly in diameter over the mandated 25 mm, perhaps to 40 mm.

But doing this gives no increase in overall mass, because I would get rid of the unnecessary tube you have added above this upper-SIS-tube, namely the tube that runs from top of FRH back to MRH. So the car has lower sides, for easier 5-second-egress test, and lower overall CG.

Also the top of Front-Bulkhead only has to be as high as this upper-SIS-tube, which lowers CG again, and gives a neater frame overall. Note that in scrutineering the footbox template only moves to within 100 mm of pedals, and here the topmost-footbox-tubes are much higher. In plan-view these topmost-footbox-tubes should converge in a "triangulating-V" to the top-centre of FRH, with the upper section of FRH being a semi-circle (in end-view), same as the top of MRH.

Lastly on structures, LONG-NARROW-TRIANGLES = BAD! So your current triangulation of the SIS, with the diagonal-SIS-tube being close to horizontal, adds much compliance to the frame. Making this diagonal-tube as a "V" in side-view can make the frame much stronger/stiffer (as per your earlier draft sketches). But if you add structural skins to the sides of the frame, then you can keep the single, almost-horizontal, diagonal-SIS-tube, because the skins will carry all the shear stresses. Once again, these side-skins only have to be 0.5 - 1.0 mm thick (1.0 mm is truck-tough!).
~o0o~

Lastly, all this rough, conceptual, "iterating" is the MOST FUN part of the whole design process. Get this early stuff close to right, and everything that follows becomes much easier. :)

Z

(PS. The green tabs attaching suspension-BJs to frame should be much wider where they weld to chassis (~40+ mm). The "three-tube" wishbones (with sphericals inserted in "short third-tube") are good. The green upright-top-clevis should be wider and attach to upright with two bolts ~30 mm apart, similar to bottom clevis. Both these clevises can be made quite easily from 3 mm thk sheet-steel, bent to suit.)

[Ahmad Rezq]

Z,


Also, while all these suggestions might sound like never-ending NEGATIVITY, they will actually make things easier for you in the long run.

Better to get rid of the mistakes while they are just sketches on post-it notes (or digital equivalent), than to discover just before comp that it doesn't work. Aaarghh!

So...

- I do agree; That's why I'am trying to go farther in every trial and share the photos and receive the suggestions, It's not only about the competition but It's for an educational purpose also.


What material are you making the axles from?

- Last year Front and Rear shafts were steel, This year we are planning to manufacture the front shafts out of Aluminium (As the manufacturer last year complain dealing with the steel, Long time in machining ((Free manufacturing sponsor)) ).

- For the Ergonomics point: I was thinking the same after finishing the side view. I made a quick model using some white tabs and i pretended to drive the car, it was fine (I'am 1.8 m Height) waiting for the Model to modify it or keep it.

- On point 3
Compromising between (Percy+steering column position and its fixations+footbox template) leaded me to this configuration the distance between the Upper BH support and the upper SI member is 260 so i had to add the tube mentioned by you (the tube that runs from top of FRH back to MRH.) It can be done better if i rethink of it again, I shall give another trial + I can as you have suggested make a V tubes in SIS with a vertical member and attach the mentioned tube to it (i.e half distance in the upper SI tube).

[Ahmad Rezq]

Z,
The footbox template is almost above the rack.

[P^squared]

Do check whether you are able to achieve a sufficiently tight turning radius while keeping your wishbone hardpoints this far apart longitudinally.

Also, the control arm bracket on the upright you designed for the loaded( connected to the damper ) wishbone might not be strong enough.

Better try the skin for the SIS. Also square section tubing is lighter, than 1.6 mm round tube and easier to manufacture.

All the Best !

[Kareem]

- two DGBB 6008-2RS1 (For 40 mm Diameter 6008-2RS1 is the only available bearing in Egypt Market).

you can check the market again Rezq. I found ACBB and ACBB, super precision.

Even if you don't need it, take a look at prices and select suitable type for design and fund.

[Ahmad Rezq]

A trial to bend the Main hoop ((It was done at a local workshop in Egypt))

- We designed and manufactured a wood guide to help the worker to control the dimensions. (Cost 77.5 EGP ~ $9.5)
852
853

- The hoop was filled with sand, heated and bent.
- The dimensions were measured on the wood guide and the hoop was modified according to the WG (The wood guide is survived from the extra heat :( )
- The bent was smooth and the final dimensions were more than acceptable.
-Cost of Bending process 100 EGP ~ $12
- Total Cost of The process $21.5

854855856

[Ahmad Rezq]

Roll Hoop Bending

857

[mech5496]

Fun thing, we are doing the same.. :P

[Ahmad Rezq]

:cool: :cool: :cool: