Suggestions Sought for New Chassis Design

Tips and tricks about building a car. painting it a making it run smooth.
Ned
Posts: 314
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: Suggestions Sought for New Chassis Design

Post by Ned » Tue 23. Feb 2016 19:01

I plan to design another chassis with an adjustable wheelbase from 3.125" to 3.750", which is 100" to 120" at full scale. I hope to make it thin enough to accommodate the low front and rear ends of the 2003 Audi R8 pictured below. This chassis will probably be designed in 3 sections, one for the front end, one for the battery and one for the rear end. This will allow the battery to be positioned between the front and rear so as to minimize interference with the car's interior & low body sections.

Image

Image

Assuming stock front wheels which are about .290" wide, what front track would you like? Of course the track can be reduced some by running narrower wheels.
Do you want to run stock wheels? If not, what diameter front stub axles would you prefer? What diameter rear axle would you prefer?

User avatar
Lasp
Posts: 313
Joined: Wed 16. Jan 2013 16:35
Location: Helsingborg, Sweden

Re: Suggestions Sought for New Chassis Design

Post by Lasp » Tue 23. Feb 2016 21:20

Its needed with space for the frontwheel, Thats a big different from the ordinary bodys in 1:32.
I have Ask Avant slot if its possible too bye bodys. Both in 1:24 and in 1:31 typical LMP

Ned
Posts: 314
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: Suggestions Sought for New Chassis Design

Post by Ned » Tue 15. Mar 2016 04:30

I finally completed the design of a small chassis that will fit my 1965 Chaparral 2C and many similar small cars.
As you can see in the photos below, the chassis is narrow enough to fit within the Chaparral body. When I shorten the screw that holds the magnet guide arm to the suspension plates, the bottom of the chassis will be flush with the bottom edge of the side panels. Several parts have extra holes to reduce weight and printing costs. Speaking of weight, this chassis weighs 3 grams less that the standard chassis.

Image

Image

The barebones chassis is shown below. The wheelbase is adjustable from 2.75” to 3.375”. The center section is only 1.93” wide compared to the stock chassis which is 2.135”. The center section is .405” thick compared to the stock chassis which is .550” thick. The front end is the same thickness as a stock chassis. There is a pocket .050” deep to hold the coil so it can be mounted .050” lower. This helps to maximize the clearance between the top of the coil and the body directly above it. A protected battery will fit in the battery box but it is a tight fit and requires a thin magnet for the + terminal.

Image

Image

Image

Image

The front end assembly is depicted below.Very similar to the stock parts with a few minor differences. The front stub axle carriers are a little heavier and they are symmetrical so they can be used on either side of the car. If preferred, the holes for the stub axles can be made bigger for larger diameter stub axles.

Image

As can be seen below, the magnet guide arm is slightly wider at the point where it is a attached by the screw and it has reinforcing ribs on the edges to make it stiffer.

Image

The upper suspension plate has 4 holes for regular #2 steel self tapping screws to attach the body to the chassis with the use of magnets glued to the body. #2 self tapping screws are also used to attach the suspension plates to the base frame. This eliminates the need for nuts on top of the upper suspension plate, which take up room. There is also no need for the tips of the screws to protrude through the top of the upper suspension plate as depicted in the photo below. This frontend design provides almost 2 degrees of toe in on both sides.

Image

The 6 pieces of the front end assembly are shown below. The pins on the stub axle carriers are slightly thicker than in the case of the standard axle carriers to obtain the strength required when produced by a 3D printer. The same is truce of the pins at each end of the tie rod (steering plate).

Image

Now it’s time to get everything put together and the car on the track to see how it performs.

kiklo
Posts: 175
Joined: Mon 9. Nov 2015 11:49
Location: Norway

Re: Suggestions Sought for New Chassis Design

Post by kiklo » Tue 15. Mar 2016 09:04

Hi Ned.

That is certainly impressive work you have done.
Looking forward to hear more from your project.
Racing Regards

Kim K.

kiklo
Posts: 175
Joined: Mon 9. Nov 2015 11:49
Location: Norway

Re: Suggestions Sought for New Chassis Design

Post by kiklo » Tue 15. Mar 2016 09:07

Are you printing with ABS or PLA ?
Racing Regards

Kim K.

Ned
Posts: 314
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: Suggestions Sought for New Chassis Design

Post by Ned » Tue 15. Mar 2016 14:13

kiklo wrote:Are you printing with ABS or PLA ?
It is printed by Shapeways in what they call "Strong and Flexible Plastic". Per their website, they start with a bed of Nylon powder and sinter the powder with a laser layer by layer, solidifying the powder as they go.

WesR
Posts: 320
Joined: Fri 21. Dec 2012 17:37

Re: Suggestions Sought for New Chassis Design

Post by WesR » Wed 16. Mar 2016 19:56

Chassis looks excellent Ned. 3D printing was not around when I started this project or I would certainly have used it.
I would be interested to know how close the hole sizes are to the specified sizes and did you allow for opening up by drilling.
Just thinking that it would be possible for individuals or teams, using 3d, to develop their own car, within racing specifications, just like full size. I guess that could be done now with slot racing. But slot racing design is not much of a challenge is it!

Ned
Posts: 314
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: Suggestions Sought for New Chassis Design

Post by Ned » Wed 16. Mar 2016 22:55

From experience I know that the location of holes is always excellent. The diameter of holes however is always .004" - .006" under the spec of the 3D model. I plan accordingly. For the few holes where the diameter is critical, namely those for which an axle or pin rotates inside the hole, like the rear axle, or kingpins, I deliberately make the holes undersized and drill them out to the exact size needed. I have about 50 carbide drill bits with 1/8" shanks for cutting holes .050" to .125", so I can usually get within .002" (.05mm) of what I think is optimal. A strand of my white hair measures .002". ;) I never enlarge the holes for the press fit magnets. Occasionally I enlarge some other hole.

Interestingly, the diameter of pins/posts (what Shapeways calls wires) is also always .004" - .006" under spec. For example the diameter of the pins on the stub axle carriers is specified at .070" but when printed they average .065". The same is true of the pins at the end of the steering plate. Looks to me like circles, whether filled or hollow, are always under spec.

Most horizontal pieces, such as the base of the frame or the floor of the motor pod are usually printed .004" - .006" thicker than specified by the model. Again, I plan accordingly. In order to get the motor pod to slide in and out easily, the bottom of the pod must be sanded a little, with very fine sandpaper and the grooves in the frame must be cleaned of residual powder with the point of a small nail. On balance, Shapeways is able to print parts accurately enough for magracing cars after just a little bit of "fine tuning".

I wish there were enough guys into magracing around here to have teams. I'd love to develop my own cars specifically for racing. My focus so far has been to make several chassis which are easily fitted to existing slot car bodies which folks might have on hand now or be able to buy inexpensively on ebay. You're right about slot racing chassis design being easy compared to magracing design. A steerable frontend really complicates things but also allows for creative design solutions to optimize handling depending on the track.

SlotCarRental_com
Posts: 41
Joined: Sat 10. Aug 2013 08:39

Re: Suggestions Sought for New Chassis Design

Post by SlotCarRental_com » Thu 17. Mar 2016 08:49

Just about all of the RP machine materials shrink after cooling and curing.

Still waiting for my own RP machine to get here, more delays...

Ned
Posts: 314
Joined: Sun 13. Apr 2014 01:02
Location: Sedona, AZ USA

Re: Suggestions Sought for New Chassis Design

Post by Ned » Sat 16. Apr 2016 01:20

kiklo wrote: That is certainly impressive work you have done.
Looking forward to hear more from your project.
The Chaparral 2C is finished. To see photos and details go to viewtopic.php?f=4&t=579
I have a few more modifications to make the chassis narrower, thinner, and easier to assemble. When finished I’ll make the chassis available to everyone on Shapeways.com . I hope the last iteration will fit my narrower Porsche 910 body.
In any case I've met my goal of developing a chassis that will fit all 5 bodies pictured at the beginning of this topic.

Post Reply