Road to 2014 Build Off

[firemanjim]

Ok, been thinking about this years build off, and my planned entry. I figured I would start a thread to put my thoughts/ideas to paper and get some feed back. Although this might not be a good idea to post all my plans and ideas for the world to see but its not like what Im doing is new and innovating,its been done before. Its all in the execution.....
With that being said, Im planning a double A arm front, IRS rear mini buggy. Im gonna start with a kart that Ive previously posted. Im going to re-do the floor frame, remove the swing arm set up, and change to an IRS set up with a solid mount engine. Gonna use a Honda 200cc atv engine for power. Looking fir speeds near 60+ in high gear set and be able to pull a car in the low gear set.
The rear set up all pivots on a 3/4" axle 44" long. I think my pics/drawings are self explanatory. Please comment,good or bad, on my idea/design. Looking for input. Im concerned with the A arms twisting with a high impact. Im using 1&1/4" stub axles about 12" long, riding on roller bearings on both sides of the housing. I will be using 22"-24" off road atv tires. Is there a way to increase the strength of the A arm to keep it from twisting? As of now, its designed with 1"x.100-.120" tube. Thinking MAYBE the straight leg should be 1x1/4"......


EDIT.... the drawn pics on white paper is to scale ,1/2"=12".... I may just use some 16-18" tires?.... not sure yet. I got a set of $$nice tires$$ for it already. We will see.....

 

[firemanjim]

Due to the bad weather coming through, it seems as though I cannot post pics. I will keep trying ,frequently,at the disgust of my wife. I get SO AGG when the internet connection is no good..... I start saying words unfit for print/hearing.......

EDIT..... OOOH OOOH, They loaded...... The pic with the tire is a 16" tire. The long scale represents the pivot axle. In the other pic, the 12"scale represents the stub axle and the 6" is the sprocket. Ok, so, what do you guys think?

 

[itsid]

Gonna use a Honda 200cc atv engine for power. Looking fir speeds near 60+ in high gear set and be able to pull a car in the low gear set.
The rear set up all pivots on a 3/4" axle 44" long.

Wait pulling a car with a 3/4" axle?
that sounds a bit flimsy for the task..
Axles on std race karts are ~2" (okay hollow of course)
but I think you need to beef the axle up at least a bit.

Due to the bad weather coming through, it seems as though I cannot post pics.

Anyways..
the arm looks a little bit short for a wheel that size,
I think it won't provide much travel and will be rather stiff (short lever)
I'd take the wheel diameter as a template for the trailing arms length (the rod; excluding the mounts)
so plus 4 to 6 inch depending on the tires you choose in the end.

Also you should take care that you keep the wheels' sprockets as close as possible to the bearings and still provide enough room.
(it seems that a 10T sprocket could catch already)
So I'd increase the length of the bearing retainer another inch or so.

'sid

 

[firemanjim]

Sid, as far as the axle goes, that is what everything will pivot on. Cant find heim.ends fir 1" axle so i went to 3/4" . With 5 pillow block bearings spread out in key points should compensate some for the small diameter. No, i wont be pulling a car, just saying.... lol
There is enough clearance for a 6" diameter sprocket on tbe inside of the housing and the secondary drive sprockets will have plenty of room. We havent gotten to that side of this yet. I will be able to run secondary drive sprockets as big as 5&1/2" if need be. This is preliminary thinking.
My main concern is the twisting . I dont want to "jump" a ditch and the stub axles/trailing arms twist . Thinking bigger tube.....
The length of the trailing arms is still in the air too,kinda. The 16" tire dont look bad, and it gets a total of 10"-12" of swing,with 7" of shock compression, perfect for my 8" travel off road coil overs.... But i might go a few more "'s in length, its just my thiught that it will make it weaker by being longer, but still only 12" wide. Right now, with the heim ends on, it would be about 19"-20" center hole to center hole (heim - housing)
The stub axles (driven axles) will be 1&1/4" x 12"

 

[fowler]

3/4 in pivot is loads

As long as it's the pivot not the drive axle

My 4x4 pickup uses 18mm (11/16) pins to connect the springs to the hangers
And that pulls 5 tonne up a sand hill

 

[itsid]

My main concern is the twisting . I dont want to "jump" a ditch and the stub axles/trailing arms twist . Thinking bigger tube.....
The length of the trailing arms is still in the air too,kinda.

Well, make a crossbar for the coilover so the load spreads onto both tubes, or attach it to the bearing retainer itself. not just the inner tube.
Then it'll be close to impossible to twist the trailing arm.
(A serious side impact could still bend them, but the frame itself will be a pretzel then, so who cares )

3/4 in pivot is loads
As long as it's the pivot not the drive axle

IIUC it's both, the pivot AND the primary driven axle (like say a jackshaft)

No, i wont be pulling a car, just saying.... lol

In that case.. I see no problem!

Oh and no heavy off roading I hope

'sid

 

[OzFab]

Just so I understand, there will be drive chains from the pivot shaft to both wheels/hubs?

 

[firemanjim]

Just so I understand, there will be drive chains from the pivot shaft to both wheels/hubs?

Yeah Tony, just like a jackshaft. It will have 3 13-14 tooth sprockets. The driven sprockets will be on the inside of the trailing arm,please refer to the pic with the 12" and 6" scales. One represents the stub axle ,the other is the sprocket.......

 

[firemanjim]

I think i solved my fear of the trailing arm twisting on the in-board side. I remembered that adding a "truss"would increase the lateral strength. So, the main tubes will be 1&1/4" x .120 and the truss and the lateral tubes will be 7/8" x .100"......
What do you think now? O, the length will be 20"-22" and with the heim ends attached,about 24" OAL

 

[machinist@large]

In your first set of photo's, I'm taking a WAG that you're thinking of using Timken bearings for the hub stub axles? If so, keep in mind that the free play adjustment will have to be inside the bearing tube with the shaft seals outboard, or you'll need to use a smooth wall sleeve in the seal zone...

To the best of my knowledge, no one lists a stock, off the shelf sealed tapered roller bearing, and I've only seen a limited range of angular contact bearing sets that have seals; and those have a breath taking price tag attached....

Pat

 

[firemanjim]

Good eye ,Pat. Yep, them bearings wont work. Non lubricated (insert joke here) bearings wont work cause im not gonna machine a sealed housing for a kart. What would you suggest for the bearings?

 

[Half-breeder]

... just asking(cause I dont know)... but will these work?...

 

[machinist@large]

... just asking(cause I dont know)... but will these work?...

Nope. That was the type of bearings we were just talking about; when used in a sealed, blind housing they work well. In a thru shaft application like Jim's noodling/ doodling over? Way more work and trouble than they're worth.

 

[machinist@large]

Good eye ,Pat. Yep, them bearings wont work. Non lubricated (insert joke here) bearings wont work cause im not gonna machine a sealed housing for a kart. What would you suggest for the bearings?

Any idea what kind of weight range you think you might be looking at? In this case, per axle (IRS= two). That also begs the question of the actual stub shaft dia. that you will end up using. I'm guessing that you'll probably wind up with a max RPM at the wheels (for a case argument) of between 850 to 1200 RPM if you actually gun for 60 MPH; that falls into the stock (meaning reasonably affordable) electric motor bearing size range. What do you consider affordable? Also, what did you have in mind for an actual shaft assembly design?

I know this is doable, but I don't have enough info to even begin to search for answers.... Sorry Jim, not enough information....

Pat