Building the beast

[Slamwoef]

Good day builders n riders.

I must admit I have started this build a month or 2 ago.

I have gone trough extensive calculations to get the chassis the rite length. Using formula h(m)8=Length. AKA Hmmmmmmmm ill make it this long.

I have attached some photos plz let me know if they don't show up.

The chassis is made from 25 x 25 x 1.6 mm tube its a double stack chassis with the lower section being smaller so that it could be braced in some sort of fasion. I spaced the front end very close together so that I can have a compact steering system ( also building this) and enough controll arm movement without sacraficing wheel width ( about 1.1meters)

The wheels are 10" steel rims for now but they will become Quad rims and tires by the end.

Power is passed to the rear wheels from a 100cc Yamaha 2stroke making about 10 Hp trough a 4 speed box. This is just a temp motor as I am also busy with a 450cc Suzuki Twin that will go in should be good for about 40+ Hp, but that still needs a lot of work.

Braking is only on the back as a go kart should drums for now. Disk will be on when the 450 comes.

Front end is double wishbone with pitman steering system, I still need to fit the shocks and springs but that should be easy. Its a bit complex but it works 100% will post photo of that by the weekend.

Sweet guys and gals.

Please let me know what you think. All comments welcome.

 

[fowler]

Looking good

That's about the usual calc for chassis length

Just read up on steering geometry to build it to your chassis length
Its rather important

 

[Slamwoef]

Thanx Fowler.

The only thing I was warried about on the steering is the accermans angle.
I needed to get that rite so I don't end up over stressing the links and chassis when turning. Got that sorted with a nylon rope and a tape measure. Seems to work well wil only realy be able to test it when all 4 wheels hit the dirt.

Its my firts suspention kart so I made my piece with the fact that some things will brake and some things will be cut off and redone. Its all part of the fun.

Thanx for your input. Always apreciated.

 

[landuse]

You have made a good start. THIS is a great read regarding camber, caster and ackerman.

What welder are you using? I was also wondering if you are going to make the engine area large enough to accomodate the larger engine in the future. What you should actually do is build this kart with the larger engine in mind. Also keep in mind that all the mounts are going to be different between the 2 engines.

 

[Slamwoef]

Thanx Landuse

Thanx for the link.

The chassis is built for the big motor but the sub frame that houses the motor is not. That will be a total rebuild as I need to house the brake caliper and change the drive terain. 480 to 520 pitch.

When I get the 450 started ill build a new subframe for it. Not to much of a hastle

On the photos I tack welded using a DC stick welder but have upgraded to a Mig using 0.8 mm wire. She welds like a dream. It will even weld mild steel to cast iron.

Like I said the front end is 90% done just need to fit the struts.

Will post pics ASAP

 

[Slamwoef]

So now I need to pick some brains now.

On the front suspention how much should the struts be pitched inwards?

The bottom of the strut is bolted to the lower controll arm close to the stub. I need to build the top for the strut but not sure how much to pitch them.

Any help will be appriciated

 

[landuse]

So now I need to pick some brains now.

On the front suspention how much should the struts be pitched inwards?

The bottom of the strut is bolted to the lower controll arm close to the stub. I need to build the top for the strut but not sure how much to pitch them.

Any help will be appriciated

Have a look at these threads. You will probably get some good info there. I personally am not too sure of suspension, as I have never had or worked on any

http://www.diygokarts.com/vb/showthread.php?t=17888
http://www.diygokarts.com/vb/showthread.php?t=19276

You will find that most of the forum members are American, so you will generally only get answers to your questions during the evening. Some of the Ausies and New Zealanders are on during our day though

 

[Nodroz]

On the photos I tack welded using a DC stick welder but have upgraded to a Mig using 0.8 mm wire. She welds like a dream. It will even weld mild steel to cast iron.

Off topic; how did the DC stick welding perform? Were you satisfied about it? Would you rather take the MIG over that DC Stick welder?

What brand is your MIG welder from and what's its max amps?


The frame is looking great. Enough bracing and a nice design so far! Keep up the good work!

 

[OzFab]

On the front suspention how much should the struts be pitched inwards?

IMO, I don't think it makes a lot of difference whether they stand straight up or lay over @30*. Obviously, there would be more travel the more they lean over & (I think) they would be harder

 

[Slamwoef]

Hi Nodroz.

Both welders are made here in SA named Mig-Mag (I think they might be cheap china made)

The DC stick is very good but it still has a standard problem that the work piece tends to pull which makes building squere a touch harder.

The mig is a lot quicker as you never need to stop for rod changing and it fills gaps a lot easyer. I'm not sure about the current rating will check for you.
The only problem that I found is the mig builds a higher bead.

Penetration on both welders is very good.

Fabroman

I was thinking 30 deg to 45 deg. At worst ill build it with a adjustable pin so I can move it from 30 to 45 deg if I'm not happy with it. Was woundering if someone has done the RnD to say which setup works the best.

Thanx for taking the time to post and the intrest in my project.

 

[exenos]

The flater the struts/shocks are placed the softer your suspension will be, it will also result in more travel. For a stiffer suspension place the shocks vertical, or closer to vertical.

 

[jamyers]

The flater the struts/shocks are placed the softer your suspension will be, it will also result in more travel. For a stiffer suspension place the shocks vertical, or closer to vertical.

Exactly. Keep in mind, though, that changing the angle of the stuts will also change the ride height.

I'd make several mounting spots for both top and bottom of the struts, that way you've got lots of adjustability.

 

[Slamwoef]

Thanx for the feedback.

I need a fair amount of travel.
I can dril the top mounting holes in such a way that it wil not influance the ride hight and the struts have an adjustable preload so tention shouldnd be a issue. Ill make do 45 and 30 deg and see which works best.

Is it wourth tilting the struts back slightly ? Maybe 10 deg? I have heard that someone said it helps slightl with front bump impact but not to sure if I believe it? Any ideas?

 

[exenos]

If you tilt the shocks back you will need to tilt the a arms back the same amount. How much does you shock compress?

 

[OzFab]

The flater the struts/shocks are placed the softer your suspension will be, it will also result in more travel. For a stiffer suspension place the shocks vertical, or closer to vertical.

Exactly. Keep in mind, though, that changing the angle of the stuts will also change the ride height.

Ok, I had that bit backwards Thanks guys

 

[Slamwoef]

Here we go, some nice photos for you guys.

just took random photos of the front end as it sits in the garage.

if there is anything in particular that you would like more detail on let me know.

the struts are of the back end of a gs450 not sure how much travel they will have but i'm sure they will be more than up to the job.

upper control arm are of a Mazda i think? the lower control arms are made from a tie rod end some 20mm tube and a M12 nut and bolt ( for slight adjustment of the camber), stabilizer link ( now the drag link)

the steering is operated from a chopped steering rack (with adjustment bolt to set steering straight) and some flat bar, you will see there is a bolt welded (at the bends) to the center link, this will allow me to adjust toe angle.

i have included 2 photos of maximum suspension travel allowed on the pivots although the struts will not do anything near that sort of movement its still nice to know the suspension will not bottom out while the strut still has movement left.

any comments as always very welcome

 

[Slamwoef]

sorry forgot these

 

[exenos]

Your shocks will be able to produce the full range of travel that is offered. I would suggest removing the coils from the shocks and play around with the mounting holes until you reach the desired travel. Then put the coils back on and adjust the tension until you have the amount of sag you want.

Having the shocks at the angle you show in that picture will give you roughly double the compression of the shock in wheel travel.

 

[Amped]

Have you accounted for bump steer? This article is a good read for bump steer.
http://www.longacreracing.com/articles/art.asp?ARTID=13
I like your frame design.Are you going to close the open ends of the tubing?

 

[jamyers]

One thing you might consider is mounting the strut bottoms to the upper control arms - Ball-joints are much stronger than tie-rod joints, the top arms are much stronger than the lower arms, PLUS then the load on the front end will be pushing that top ball joint "together", instead of trying to pull the lower tie-rod joint "apart".

It might make more height in the front end, but you'd be much less likely to have a joint failure. Then again, you might find that mounting them all the way out at the end of the upper arm (less leverage) might offset laying them over some more (more leverage).