Urba Centurion Update - (Kubota diesel, 100+ MPG in mixed driving - Fall 2012 on)

[changzuki]

Thanks for the positive comments!

Not included in previous posts are these couple items:

The original Centurion with its 750 cc Kubota has an add-on belt driven water pump which leaves little room for anything else not to mention lots of rubber hose.... (Not sure about the Lane Museum setup..) This also pretty much limits the possibility of ever using any alternator other than the tiny Kubota generator unit since that pump occupies precious room where a normal alternator could go. Something to think about if anyone is going to build one of these and is planning on running much of any electrical load and trying to keep a battery charged..

The Centurion in this thread using the 850cc has a normal style water pump and a 100amp 80's style Delco alternator. These alts are very inexpensive to buy, maintain, and remove if necessary. The Kubota exhaust manifold is wrapped to keep the heat away from the alternator.


Original Centurion (left photo)..............................CrazyJerrys Centurion (right photo)

I also use a 3.27 differential. It's a new unit from Quantum Mechanics that's advertised to be more stout than the factory 3.27. The original 1966 differential contained a 4.11 ring and pinion which would be great for pulling stumps on the farm, but with a straight 4spd is a poor match for the 3000 rpm of the Kubota. I could only get about 45 mph with a 4spd and that 4.11 however, at idle I could dump the clutch and it would not even come close to stalling.





This car has no power brakes and no power steering. Due to the light weight neither is necessary. It can stop really quick with a mild press on the pedal, and it steers easy and go cart-like. It will corner like a slot-car, to the point where I hope the body mounts are strong enough. Parallel parking is easy if you can see your corners..

Both the Original Centurion and Lane's have the rear view mirror on the windshield like a normal car... With the rake on mine, that mounting location is completely useless. I had to mount it on the dash..

The Original Centurion had no exterior door mirrors and Lane's had a gigantor set of Mickey-Mouse ears (maybe that's why they only got 45 mpg!)



I decided against cctv for rear view and went with 2 Wally World bicycle mirrors. Since everything else is about 3/4 scale they fit right in!

If anyone builds one of these, don't overlook the muffler. I had a single setup like the Original Centurion but after several configurations I baffled a single-in dual-out muffler. The engine behaved differently over the rpm range with each one.

For the flip-up headlights, the Original Centurion uses an electric motor out of a 70 Charger (like the General Lee!) to open and close them. (Price one of those out on eBay - incredible!!!) Well, I'd like to see how great that actually worked on the Original Centurion. My experience was the flip-ups are too heavy and the motor isn't nearly strong enough. In fact my fabricated square stock linkage (per the instructions) has actually twisted a bit. I ultimately changed a couple of pivot points and put a manual cable pull on it (with a thumb lock). I also got some lightweight plastic 6054 headlights to replace the heavy glass units. The flip ups work real quick now.





Not sure of a build thread for the Tri-Magnum, but an update thread is not out of the question! Possibly starting this fall. I have 2 possible donor bikes and one is a 1980 Honda GoldWing 1100 Interstate, the other is a 1985 Honda GoldWing 1200 Interstate. After doing a single VW carb conversion on it, I've been driving the 1980 for a month now to see if it's "The One"... It seems pretty bomb-proof and lots of power. The 1200 is simply too nice to bust up but who knows... Will reveal more in the Fall on a new thread...
~CrazyJerry

[GreenHornet]

Hey Crazy Jerry,

Good choice on the Quantum Mechanics differential. In my opinion the 3.27 is the way to go for the fuel economy. The later GT6 3.27 differentials were more robust than the MK1,MKII and spitfire units. Most likely this is the case they sale. As far as internals they are most likely a hybrid as the GT6 gears were actually not the strongest!

The major problem with a GT6 and Spitfire differential is failure of the crown wheel carrier due to fatigue. All Mk I and II diffs suffer like this and non overdrive Mk IIIs. (3.89 Mk III diffs are much better and less likely to fail). A car that is driven hard will tend to suffer earlier but there is also an element of luck involved. When the diff is out of the car the rear case can be removed and the carrier checkd for cracks very carefully just under the crownwheel teeth. The longer the cracks the shorter the life particularly if even more torque is put through it.

There is a hulk version of the 3.27 diff carrier (part number RKC2802) that is virtually indestructable, but it was only fitted from around 1977 and never to a GT6 go figure. You could find it on the Ital 2 litre auto, Swiss Spitfires, Dolomite 1850 Auto, and TR7 auto with four speed axle.

Most people today would look down on a vehicle that does not have power steering or power brakes. I find it to be more efficient and a huge reason to use the Spitfire/GT6 chassis as a kitcar design or super efficient one off dream car build. It is hard to beat simplicity and the original Spitfire exemplifies it.

I really like your side mirror selection now can those flip inwards also by chance?

Good talking with you Crazy Jerry and thanks for sharing more details of your Centurion. I am really enjoying our discussion here and this thread

GH

[93hatchDX]

What's the ballpark price tag of a build like this ?

[samwichse]

You should drive it in reverse for the best gas mileage



:-P

[exccel]

I am new to this site. Although I have undertaken numerous, engine changes, transmission, rebuilds etc this Urba centurion is just getting started. Thanks for your comments. I have just got the engine a Kubota 905 and the Triumph engine out of their respective vehicles/equipment. I meet with a machine shop tomorrow to modify the Triumph flywheel to fit the Kubota engine. The K905 runs like a top--a real steal at auction and I got a light tower, a trailer and 5KW generator with it--all in working order!! woo-hoo
My plans are to bench test the drive train and "no-load" MPG over a couple of gallons of diesel fuel. Then I will know whether I will continue and rebody etc or call it quites and put the gen, Kubota and lights back together and sell it.

[I] bought the original plans for the Urba in 1985

Mark

[Aero]

The car looks and [I'm assuming] performs spectacularly!

[elhigh]

HOW HAVE I MISSED THIS ALL THIS TIME.

I loved these little homebrew kits back in the day, but of course never got around to building one.

Hey! Are you the same Changzuki that bolted a Chinese diesel into a Suzuki frame? I found that via web-wandering, reading up about Listeroid diesels and Detroit Diesels, not sure how I found you exactly. But that was an interesting build. Do you still drive that thing?

And do you still have those teeth?

[changzuki]

--- 93hatchDX "What's the ballpark price tag of a build like this ?"
>>> Well, skies the limit if you go all out and pay to have everything done..
I've done alot of scavenging for used stuff and that has been offset by some brand new purchases too. This project is pushing the upper end of 6k now, but almost a third of that was for the wheels that are off the original Centurion.. Took me 2 weeks to wetsand, polish and paint them but all worth it in the end....
~CrazyJerry

--- samwichse "You should drive it in reverse for the best gas mileage"
>>> Likely some merit to your statement, but the goal was to replicate the original Centurion since the only other example was Lane Motor Museum's with a reported (paltry) 40mpg in normal driving, and the question for me was - could it come close, or even break the 100 mpg barrier like the plans/write-up said? The Tri-Magnum I'm into at the moment is closer to the aero-shape you referenced than the Centurion is. Should be interesting!
~CrazyJerry

--- exccel "this Urba centurion is just getting started. ...Then I will know whether I will continue and rebody etc or call it quites and put the gen, Kubota and lights back together and sell it. Mark"
>>> Mark, I applaud you and your undertaking is a huge commitment. If you are realistic in your expectations and see it through it is very, very, rewarding IMHO. If you have any questions about the build as go, I'd gladly give you my 2 cents. The RQ Riley plans are solid and are well thought out especially for the era, but there's a few things that can be improved upon too... Good luck and please keep your progress posted when you can - ~CrazyJerry

>>> Aero "The car looks and [I'm assuming] performs spectacularly!"
--- Yes - but then again I'm easy to please! The goal was to out-mpg the Changzuki (115mpg diesel motorcycle) I did back in 2004. The Centurion does that and more, so your description is exactly my experience - thanks!!!
~CrazyJerry

>>> elhigh "HOW HAVE I MISSED THIS ALL THIS TIME..... Are you the same Changzuki that bolted a Chinese diesel into a Suzuki frame? I found that via web-wandering, reading up about Listeroid diesels and Detroit Diesels, not sure how I found you exactly. But that was an interesting build. Do you still drive that thing? And do you still have those teeth?"
--- elhigh! As with most of the projects, I try to keep a low profile, blend if you will.
And yes I am the same CrazyJerry with the Changzuki (Changfa/Suzuki) sporting those beloved teefs! That bike has been flawless for about 15,000 miles now. Even the chrome sinkdrain exhaust pipe has held up! If you mill around the net and are into off-grid / Listeroids / or items that steer in that direction then you probably ran across a mention of me. Thanks for the post - I wasn't expecting it and actually gave me good laugh! Happy Labor Day to you!
~CrazyJerry

[exccel]

Just a quick note Jerry-I just got the Triumph Flywheel back from machine shop, put the Kubota ring gear on it and bolted up to the bota 3 cylinder. I hope to do a run-out on the flywheel to make sure it is true with crank etc. A little different than what was recommended but what the heck--so far I didnt have to fight/find a Bota flywheel to fit. The Triumph flywheel, pressure plate and clutch will fit just fine!! It is a journey!! LOL

[changzuki]

exccel,
You're moving right along and I'm diggin' it!
Not sure of your motor mount arrangement on the K905,but the original Spitfire's mounts are being used on this one. They're flipped over and that allowed a nice 90deg bracket (engine-to-Spitfire mounts) to be used. I do wish the Spitfire mounts were a tad more squishy. At idle you aren't going to stack up champagne glasses anywhere on the body or engine. Anything over 1200 rpm is a non-issue though.

Keep up the good work and I hope your flywheel runs true.
~CrazyJerry