Axle angle...

[carnut169]

At what angle can an axle be run until efficiency is lost?

Background:

We are attempting to use the existing VD rear suspension on our conversion. Where the axle normally runs the sprocket will hit the lower wishbone. We can solve this problem by moving the axle assembly closer to the engine but the axles will not be exactly straight... more like a / \.

We may also adjust chain tension by having the engine on sliders instead of the rear end. This will complicate some things (cooling, exhaust, dry-sump stuff) but we are thinking that we can engineer some movement into these items. We are only talking about less than 2" of adjustment. Still on the drawing board.

They have started cutting....

[Purple Frog]

I bet Richard Pare would know. 317-273-0089

I have seen axles in the configuration you mentioned probably over 25-30 degrees.

Something rubs me wrong about moving the engine back and forth... but what the heck, they do it on karts.

[JHaydon]

I snagged a GKN booklet at PRI. They say the tripod joints (i.e., Van Diemen) can be used at "angles up to 25 degrees only for applications up to 2000rpm."

If you have converted to the 6-ball style joint, GKN rates them to up to 22 degrees at 8000rpm when using the accordion boot or 10 degrees at 2000rpm when using the aero boot.

They say a lot more about "low friction" and other blah blah rah rah, but no more numbers or charts or graphs of friction vs angle of operation.

[John Robinson II]

Have you talked to any of the DSR guys or Craig Taylor? Why try to reinvent the wheel when others have already plundered??

John

[R. Pare]

I don't have the old GKN efficiency charts here in front of me, so I'm going off of memory......

As I recall, the tripos and ball type were pretty even efficiency-wise up to about 10 degrees, where after that the tripos joints were clearly superior. Personally, I would really try to limit the angularity to 10 degrees maximum for the sake of longevity. Remember, every revolution causes each bearing to roll a certain amount, wasting power and causing wear. A little bit of travel is desirable, but getting it up around 20 degrees will definetely shorten their life.

[David Ferguson]

Have you considered flipping some of the arms over? I mean running the left arm on the right side, but located behind the upright instead of in front. Just use the left upright on the right, etc. I don't know if that will help you, but you should consider all manner of re-using parts when your doing your engineering (er, Van Diemen bodging?) on the fly.

I think it's a bad idea to move the engine -- you would probably be better off with a chain tensioning mechanism. Remember gearing on these things happens by changing the rear sprocket, so you have to accomodate a large range of sizes. On our Stohr DSR, we have two chains (one has 2 less links than the other), and an adjustment range of about 1.25 inches. We run sprockets with 42 to 49 teeth.

[carnut169]

Thanks guys!

Still working on it....

[kladendo]

As an active Dsr driver/builder I would advise against moving the engine as a means to tension the chain, there are a number of clever ways to design a sproket carrier that contains the sproket, a short axel, two bearings and attachments for the drive axels. The method to tension the chain is to rotate the carrier about a lower pivot and upper slot , The upper slot has a slight radius to allow the carrier motion front to rear. For a lot of chain drive cars the lower pivot is positioned at the point where the carrier is vertical and the axels are straight in plan view ( looking down from the top) The upper slot is 3.00" in length. When the carrier is vertical (the upper pivot bolt is aligned with the lower pivot bolt) 3/4" of the slot for forward adjustment, 2 1/4" of adjustment to the rear. Upper and lower 3/8 -24 bolts to clamp the carrier in place. A 7/16 or 1/2 bolt is positioned in the rear bulkhead that can bear against the carrier. You will need to get a long bolt and thread it for the 3+ inches of length for full adjustment Generally two plain nuts are used on the adjustment bolt. Tighten the chain to have about 1/2 of slack at the tightest point. (the sprocket will have a high point this is where the chain tension is checked from). This component of your car needs to be reliable and strong, A broken chain can trash a motor, frame, axels and any tanks that are close by. Chains do break usually because of misalignment which results in overheating. Check chain tension each and every weekend of use. Replace it immediately if you see signs of overheating, broken orings or it feels funny as you check or adjust. Use only the best oring chain and if possible the rivet style master link. The pivot /slot dimensions above will allow you to remove most sprockets by moving the carrier forward and winding the chain off the rear sprocket or pulling the engine sprocket off the output shaft ( at least that works on my ZX-10). GOOD LUCK with your conversion hope this helps with some of the decisions.