I only got about 20 minutes in this morning because I had some snow removal to take care of first. That said, I was able to grab this idler sprocket, and add a very large washer so it sort of fits in the output shaft hole.
With the clutch cover removed, I could now take a good look at the angles involved...
It's really just going to be like a solid frame go kart, and for the challenge, autocross, and drags all being on pavement, I think that's ok. Obviously suspension has it's benefits, but that's quite a rabbit hole.
AWSX1686 said:It's really just going to be like a solid frame go kart, and for the challenge, autocross, and drags all being on pavement, I think that's ok. Obviously suspension has it's benefits, but that's quite a rabbit hole.
for now, that's exactly the plan. also, my underfloor aero MIGHT be more consistent if the distance between the car and the ground is consistent.
Here's a quick look at my angles. I was hoping that I'd be able to take the chain under the shift rod (yellow hole), but with that red clutch cover bolt hole and the fact that this pictured sprocket is 15T and I plan to use the stock 17T sprocket which would be a bit bigger, I'm not sure that the chain can fit through there at all.
The other option is to lower the engine approximately 6 inches. Which actually might be ok, except I will have to find a solution for the exhaust. The green lines show the approximate lower chain angle needed for the chain to go above the shift rod.
I like lowering the engine for a lot of reasons. Namely it makes my side plates a LOT smaller (saves material cost, makes them stronger, etc), but it also takes something that is a significant portion of the weight of the car and lowers it by 6 inches, so that will have a real effect on final center of mass. I really don't like figuring out a new exhaust solution. The stock header is titanium and I can't weld that. I don't want to spend time re-doing a brand new header (I also don't want to downgrade from titanium!). But I may be able to cut the frame a bit for the needed clearance, and then reinforce.
You might know someone who can weld Ti, but I promise even the filler rod alone is not Challenge budget friendly.
Something to look into would be moving the output sprocket away from the case. I planned on an extension shaft to move the chain line away from the engine and gain clearance on several potential interferences.
Check out how the driveshaft is setup on Dwarf cars. There are several output shaft adapters available that use a Spicer u-joint yoke also for building your own extensions.
I don't know anything about bike engined cars (or bike engined bikes, for that matter) but could you add an idler to change your chainline?
I think an idler may be a good idea, and if made adjustable can help get tension just right.
Personally, I don't think I would try to space out the sprocket from the engine as that would put a load more load on the output shaft for an engine that is still going to be moving a lot more weight than originally intended.
Lowering the engine seems like a great idea, would it be possible to flip the exhaust upside down and have it exit obnoxiously out the top? I haven't gone back to look at any pictures of the exhaust yet.
AWSX1686 said:flip the exhaust upside down and have it exit obnoxiously out the top
Came here to suggest the same.
Why not lower the engine, leave the header the hell alone, and rebuild the crossmember to clear? Seems like the simple solution here....
Decided to take my lunch in the shop today to catch up on the time I missed this morning (actually I did it because I know you lot don't like to wait).
I took this shot to show thst spacing the sprocket away from the engine probably creates more problems than it solves. But definitely a good thought. Also had no idea ti filler rod was expensive...
Next idea is the idler sprocket. I can definitely do that, and will if I need to. The f440 came to me with and idler setup, so it wouldn't be too hard to adapt, and is an already-in-budget solution.
As for pointing the exhaust up, it's another great idea but actually due to angles involved would mean I'm pushing the driver forward another 10-12 inches.
Lowering the engine and modifying the cross member to fit is definitely the best solution, I think. So I busted out the levels, tape measure, angle gauge, pencil, and sawzall.
From lots of space:
To much less space:
So far I think this is a big improvement. I've lowered the engine about as much as possible before the exhaust hangs down below the bottom of the frame rails (which are already quite close to the ground at about 2.5 inches of elevation).
Plus some more MS paint engineering:
Still not 100% in the clear yet, but much closer. I moved the engine down about 5.5 inches in the back (and a little more in the front to get the oil pan level).
It's a Challenge car with zero suspension travel. 2.5" is more than enough ground clearance, and I think you could go lower. Just cut any frame that gets in your way and reinforce later.
Plus think of the spark show a titanium exhaust would make!
maschinenbau said:Plus think of the spark show a titanium exhaust would make!
I think lowering engine was a good idea, you can always add the idler if it does not give you all the clearance you need.
If you add the idler pulley would that mean you would not need a sliding engine mount?.
Re: idler, I'd probably just do the simple solution and have a fixed idler, meaning I'd still need to slide the engine.
84 hours. I played around a bit more this morning with header placement. I think I mis-remembered or mis-measured yesterday. With motor in this position, headers are only 1 inch above ground (1.5 inches below frame rails).
I don't like that because I don't want the headers to hit something significant at speed...
Also I tried this again just for fun:
It may be time to start heating and banging on these headers.
If the header is Ti, can you srap it for $$$ and just build your own exhaust?
Mental masturbation ahead:
Flip the engine around, and move the axle sprocket to the outside of the swing arm on the right side. Chain runs from the output to an idler, forward of the engine, driving a jackshaft on the "backside" of the chain to reverse the rotation of the drive chain that goes to the axle.
Exhaust runs straight out the back or up thru the decklid, problem solved 
Damn. This thing is pretty sweet!
In reply to Robbie :
So before you go banging on headers, realize how much total incremental height you will gain by banging on them. The answer is about none. Say you flatten them 0.5". Now you have 1.5" of clearance compared to 1.0"? Thats not significant enough IMO. Look at it with your fingers/tape measure. lol. So just let the ground do its cheese grater thing and roll with it?
Even if the headers scrape, so what? They're screwed if you bang them flat, and screwed if the ground does it for you?
I'd leave this detail until the very end? If it clears now, move onto other more significant issues you will no doubt be facing.
Exhaust and intake changes are expected once the car is done, and may even change due to other design constraints.
Edit: Also, nice work, can't wait to see it next weekend!
maschinenbau said:If the header is Ti, can you srap it for $$$ and just build your own exhaust?
I'm not sure what it scraps for, but they go all day on eBay for $50 or less shipped lol. I'm assuming they scrap for less than that, otherwise I'm going to start a business!
In reply to gumby :
I MIGHT want to see where you get your mental porn...
Lof8 - Andy said:Damn. This thing is pretty sweet!
Thanks! Hopefully it drives someday!
In reply to RACEC4R :
It doesn't clear currently. It did when I had the engine way up high. So I'm just trying to find the best balance of where the large items go, and the best balance of consider that before you make it permanent and leave that till the end.
I do have an idea to tilt the motor back slightly though, and while I'm not worried about headers scraping the ground, I am worried about them slamming into a pothole or something.
In reply to Robbie :
Ah, I skipped the whole "it doesn't clear anymore"...
13" wheels. Solved.
Or 15s with a 205-50
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