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PostPosted: December 18, 2017, 1:54 pm 
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Joined: October 10, 2010, 10:26 am
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Location: Bakersfield, CA
I'm researching my next BEC project, and I'm wondering about transporting it to events, specifically flat towing it with a tow bar..

While not an ideal way to move the car, I'm just wondering if I could.. In this case it would be a wet clutch bike engine/tranny, with the countershaft (front) spocket converted to RWD driveshaft flange (the engine turned sideways in the car; car now has a driveshaft directly linking the engine to the rear differential)..

So the question is, could I leave the bike motor in neutral, and let the differential/driveshaft 'free spin' while the BEC is being flat towed? In short, will I hurt the bike motor/tranny doing this?

thanks-

--ccrunner

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PostPosted: December 18, 2017, 2:43 pm 
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Not sure how the trans would like that but I'm pretty sure the chain and sprockets would hate it.

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PostPosted: December 18, 2017, 2:55 pm 
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I do not believe he has any sprockets based on his description. I guess it depends on the engine. I would contact the manufacturer or check the owners manual to see if its OK to cradle tow the bike that the engine came from. The items of concern would be no oil pressure and no cooling. Might be OK in both cases...might not...which would result in sad faces.
I would trailer it in any case...

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Last edited by JPS Europa on December 18, 2017, 3:51 pm, edited 1 time in total.

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PostPosted: December 18, 2017, 3:40 pm 
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I don't have any experience with flat towing, because it has never made sense to me. The thing that I would be concerned about, is hitting some bumps, and the transmission accidently engaging. Don't know if that can happen, but it would make me nervous and worried, and ruin the trip. The skilled fabricator you are, you should be able to put together a small trailer in a heartbeat.
I have towed racecars (Honda Civic) on a dolly and found that to be a pain as well. Guess what corner got bent, 1,000 km from home? At least with a trailer and a bunch of track side help, you can heave it on and get home. Did I mention you should build a trailer? :rofl:

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PostPosted: December 18, 2017, 4:04 pm 
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Joined: September 19, 2009, 12:33 pm
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The internet is split on whether bikes can be flat-towed. As someone said, it probably depends on engine design, what's spinning when the trans output shaft is spinning, and if the internal components are splash-lubricated or pump-lubricated.

This site sells a motorcycle towing dolly that lets the rear wheel roll on the ground, and they say

Quote:
1. Do I need to remove my chain?

We have never had a problem with either chain or belt
drive. If you have a drive shaft while we have never
had anyone report a problem but please check with the
dealer

2. Will it hurt my engine?

If the transmission is in neutral nothing turns but the
tire and chain/belt. There is no torque on the trans so
there is no heat generated.


But I'm not entirely comfortable accepting technical advice written in Comic Sans.


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PostPosted: December 18, 2017, 4:11 pm 
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C'mon Martin, a trailer would be the easy way :lol:

If I build this (BEC) car, it will be so light and so small that I could even drag it around behind the Volvo... I know that isn't the first choice for a tow vehicle/setup, but man, it would be cool getting good mileage, driving my little air conditioned sweetie Volvo to a fun event, while dragging the little deathtrap along.. Even a small trailer would preclude me from using the Volvo, then it's into the 12mpg truck :(

Not sure any of this is realistic; just trying to learn my options going in..

--ccrunner

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My '72 Honda N600 build log (bike engine in a microcar)...
viewtopic.php?f=36&t=14452

My '63 Volvo 1800 with a turbo inline 4 build log (LNF Ecotec compliments a Svelte Swede)
http://locostusa.com/forums/viewtopic.php?f=36&t=16309


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PostPosted: December 18, 2017, 4:23 pm 
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You're pretty cool, but not that cool. :rofl:


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0922c6e34883d0a3846261e17ea91221--haul-rennsport.jpg [ 122.9 KiB | Viewed 507 times ]

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PostPosted: December 18, 2017, 4:36 pm 
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Laminar- thanks for the link.. interesting and very clever setup..

Martin- I will live all of the rest of my days and never even approach being that cool :mrgreen:

--ccrunner

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http://locostusa.com/forums/viewtopic.php?f=36&t=16309


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PostPosted: December 18, 2017, 5:55 pm 
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How hard would it be to disconnect the driveshaft from the differential?

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PostPosted: December 18, 2017, 8:14 pm 
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I'd drop the driveshaft. A lot of bikes aren't happy with cradle towing.

Either that or spend the bucks on a Quaife reversing box. They have a neutral position.

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PostPosted: December 18, 2017, 11:08 pm 
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+1 for the reverse box.. That's instantly what came to my mind too.


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PostPosted: December 19, 2017, 11:46 am 
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Take a look at the transmission drawing. If any of the teeth driven by the output shaft dip into oil, then you're good to go. Otherwise, it's questionable.

Wreckers front-towing RWD cars drop the driveshaft if they're going to tow far; a friend's rule of thumb was 20 miles, since some car transmissions have no lubrication to the output shaft yoke unless they're in gear. I unbolted my share of driveshafts and zip-tied them up when helping out.

If you provided for access to the differential yoke, you could do the same thing; unbolt the shaft and zip tie it out of the way while towing. It might take less than five minutes. Given that it's essentially free and guarantees no harm to the driveline, I'd recommend going that route.

Do note that backing up a flat-towed vehicle more than a few feet usually doesn't work, and if the towed vehicle doesn't have much caster, the front wheels might skid rather than make tight right turns. Neither is a deal-breaker - I've pulled a lot of cars with a tow bar - but they were "learning experiences" I could have avoided if I'd thought things through before trying them...


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PostPosted: December 19, 2017, 12:46 pm 
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A few weeks ago I emailed Quaife to insure that their inline reverse box is in fact a Forward/Neutral/Reverse (FNR) as I'd always assumed it was.. Glad I reached out, because it has only Forward or Reverse- seems there is no Neutral in the Quaife unit as I had hoped, which would have solved this flat tow issue for me- so I'm onto looking to get 'neutral' in a different way..

In my quest to find a light rear diff at about a 3.0 ratio- link- viewtopic.php?f=5&t=19162 -Locoster cs3tcr suggested a Toyota Rav4 unit.. the ratio is right, and they are small and comparatively light.. So what does this have to do with flat towing?

I learned that the early Rav4 diffs (1994-2005) are very conventional, and despite being an iron housing (heavy), would surely work for my needs (although no benefit as far as flat towing goes).... But I accidentally discovered that the later Rav4 diffs (2006-2012) have an "electronic coupler" on the snout (red box in pics).. basically these Rav4s are front wheel drive vehicles, until the Toyota computer senses the need for 4 wheel drive- then a current of varying intensity is sent to this magic coupler on the rear diff, engaging the rear end to whatever level of traction is needed: It seems this coupler is really just a tiny wet clutch which is electronically activated..

So here's the question for those who know of these things.. Could I use this (2006-2012) diff and take advantage of this built in coupler to act as an electonic driveshaft disconnect? In the BEC, when flat towing, no current to the coupler means it's unlocked (like it is in the Rav4 most of the time), then when I want to drive the BEC, just jump in, flip a switch (maybe simply "ignition on" B+ fed to the coupler), and have the rear end 100% engaged (whatever level of current/volts/watts/ohms/whatever that would be?- electrical theory is not my strength :) )..

I'd love to use this later Rav4 diff to get the disconnect benefit.. it would be a neat little trick that would have real world use for both me and an eventual buyer, as this little car will just be a toy... it would be so cool to just quickly and easily drag it to events without the hassle of a trailer..

My backup plan is to see if the bike motor can tolerate a flat tow, but really my 1st choice is to employ this late Rav4 diff.. certainly not for it's intended use, but it would seem to suit my BEC needs, wouldn't it?

As always, I appreciate your thoughts :cheers:

--ccrunner


Attachments:
rav diff 1.png
rav diff 1.png [ 221.46 KiB | Viewed 418 times ]
toyota rav 2.jpg
toyota rav 2.jpg [ 76.99 KiB | Viewed 418 times ]

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My '72 Honda N600 build log (bike engine in a microcar)...
viewtopic.php?f=36&t=14452

My '63 Volvo 1800 with a turbo inline 4 build log (LNF Ecotec compliments a Svelte Swede)
http://locostusa.com/forums/viewtopic.php?f=36&t=16309
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PostPosted: December 19, 2017, 2:37 pm 
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Those rear couplers would work as long as they don't incorporate a viscous torque-splitter.

I'm working with one right now (Mitsubishi Outlander) that shows 2.2 ohms, so about 6 amps of current draw.

My uncle used to tow his bracket car (Camaro) to the track with free-wheeling hubs and skinny tires in the back.

Most of the newer front axles on 4x4's use a disconnect on one axle. Going down the road the disconnected axle spins backward, the driveshaft is static. Only works on open diffs though.

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PostPosted: December 21, 2017, 11:50 am 
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... another thought I had to allow flat towing would be to fab up a small rod/arm that I could put in place to manually depress the clutch pedal while the BEC is in tow.. Sort of like jamming a broomstick up under the dash and down to the clutch pedal to keep the clutch pushed in... Between the bike motor being in neutral, and the clutch pedal (securely!) pinned to the floor while in transit, I'd think that would successfully isolate/disconnect the motor from the spinning driveshaft :?:

--ccrunner

_________________
My '72 Honda N600 build log (bike engine in a microcar)...
viewtopic.php?f=36&t=14452

My '63 Volvo 1800 with a turbo inline 4 build log (LNF Ecotec compliments a Svelte Swede)
http://locostusa.com/forums/viewtopic.php?f=36&t=16309


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