FJ2400 - Bonneville Land Speed Racer

[freakhousecustoms]

...  I was at 45º rake with The GloWorm and this time around, I think I will be keeping the rake at 35-38º.  I think stock is 35º?

I just went out and measured... I believe stock is 28º, there's 35º on my dragbike, so I'm pretty sure I'm going to limit this build to a maximum of 35º rake.
40º would be too much and even 38º, I think, is more than I need.

[fj1289]

Spot on - the FSM says 27.5 degrees. 

I wonder when some of us jack up the rear ride height how much it is decreased?!

I'll have to go out to my trailer and dig out the plate - but yes, similar to that.   If nothing else it can be an easy template. 

[fj1289]

Here is the plate and the sprocket:






Don't know how much of a template this can serve as in reality — looks to be more chassis specific than engine specific. 

This was buried in some boxes that came with a couple billet transmissions i purchased recently.   They were in a last bunch of parts that were part of Rod Mumford's estate.  Also found a very interesting clutch setup while digging through the boxes.   Looks like an FJ back plate, but it is a VERY bizarre clutch setup.   I'll post more of it on my dragbike project. 

[fj1289]

Holy cow!  The pictures worked on the first try!  2021 is looking better already!!!

[freakhousecustoms]

 
WHOA!  Yes, that looks massive (and awesome)!
Says the guy who's outboard bearing support is going to be 2-feet long!

Looking at that sprocket reminds me to ask the question:

Are you still using the stock chain size & sprockets?  I bought before I thought and I will be using the stock sprockets to build my "driveshafts".

[fj1289]

Those "parallel" sprockets are one of the methods I was thinking of.   Haven't thought a lot about coupling two engines - fun problem set!

I've got countershaft sprockets from 15 to 20 teeth.  16, 17, and maybe 18 offset sprockets (only 3/8" offset!).  I  can confirm 19 teeth clear the cases and clutch push rod - haven't tried the 20 tooth yet.  I use a 530 chain - non o-ring drag race style chains.  I'd think an o-ring chain would be smarter on the salt.  

[freakhousecustoms]

I've got countershaft sprockets from 15 to 20 teeth.  16, 17, and maybe 18 offset sprockets (only 3/8" offset!).  I  can confirm 19 teeth clear the cases and clutch push rod

Excellent to know.  My 18T sprockets showed up last week, I ordered 6 of them, so I have 2 chances to make the driveshafts correctly. 
I just have to get some "lathe time" set up with my buddy so I can get that step crossed off the list.  Since everything is welded, I'm kinda "stuck" picking one size up front and going with that.  When I ran the GloWorm in 2019, I had a few different rear sprockets on hand, but after running, I don't think any of them were actually small enough.

How small did you go on the rear sprocket for the CO Mile?  I'm thinking I'd need to get down to a 30-32T back there... with 2 engines, I won't be lacking any torque. :-D

[fj1289]

I had a 27 tooth on the back - with an 18 or 19 on the countershaft.   I think the smallest you will get on the stock rear is 38.  I run an old school PM Chicane rim with a solid rear hub - so you can run a ridiculously small sprocket. 

Maybe you can fab a spacer for the cush drive to allow you to run a smaller sprocket?  Especially since you are going to be modifying the drive line already.

[freakhousecustoms]

A 27!  Perfect - that reinforces my thinking that I need a S M A L L sprocket. 
I'll cross that bridge when I come to it, but if push comes to shove, it shouldn't be too (relatively) difficult to fabricate/machine/cobble together some small stuff.

Thank you!

[freakhousecustoms]

The VERY FIRST episode of The Juggernaut Build has finally arrived:
The actual name is the "F'n Juggernaut" (see what I did there... F... J...  )


Click the pic to view it!  




Please Like & Subscribe on YouTube!

[fj1289]

I've got some good gearing spreadsheets from the purple sage trading post site (purplesagetradingpost.com - good land speed site if you haven't wandered across it yet).  

I'd gear for your calculated top speed and add maybe 20% for tire slippage.  

I'm guessing with two stock engines in a naked style frame, you should end up right around 200 mph.  An 18/31 or 22/38 combo would gear you for 205+/- assume zero slip.  

If you can build a flange into your outrigger output, you could change the "front" sprocket (using a bolt-on rear wheel style sprocket) and achieve pretty much any gearing you desire - even if you leave the stock sprocket carrier stock and be limited to a 38 tooth rear sprocket.  

edit - just realized those calcs were based on a 17" tire - the stock 16" size is actually a bit taller so would give more speed...

[freakhousecustoms]

Purple Sage is an invaluable resource, not only to land speed racers, but anyone who's curious about "how gearing works".
Tire slippage seems to be that X-Factor that increases exponentially as I add engines! LOL!

[freakhousecustoms]

This is where I start having fun!  She's a quick/short episode so I hope you enjoy it as much as I had fun making it.

Click Pic for Video:

[fj1289]

Anyone seen "The Greasy Hands Preachers" on Amazon Prime?

An Indie film I'm sure not for everyone - bit touches for me some of the "why's" for loving this hobby and doing some of the things we do.

Looking forward to "doubling up" the frames!

[fj1289]

Does 15-20% slippage jive with what you've experienced?  If I remember correctly that was kind of the range I was expecting to see. 

Scott Guthrie has a series of articles where he talks about twin engined bikes and cars.   The simplified logic was for salt beds more weight = more traction and more power = more speed, so adding an engine gives you both!