Thanks for bumping this thread; I can't believe I missed it before. This is one jaw-dropping build.
Thanks for bumping this thread; I can't believe I missed it before. This is one jaw-dropping build.
Maybe the hive has a solution to my current problem...
The Raby 2300 has a 7000 redline. Unfortunately anytime I rev over about 5000 the monster throws off the fanbelt.
I've tried a few different belts with no success. I'm thinking the original '70s design never intended to spin the alternator that fast.
It sort of limits me to driving shorter distances (20-30 miles) during daylight hours. Just running on the battery only.
Any solutions out there?
Purple Frog (Forum Supporter) said:Maybe the hive has a solution to my current problem...
The Raby 2300 has a 7000 redline. Unfortunately anytime I rev over about 5000 the monster throws off the fanbelt.
I've tried a few different belts with no success. I'm thinking the original '70s design never intended to spin the alternator that fast.
It sort of limits me to driving shorter distances (20-30 miles) during daylight hours. Just running on the battery only.
Any solutions out there?
What about a fanbelt tensioner? There are a couple of ideas on the CB Performance page, but mostly for multi V-belts and type 1 cooling tins, but using a VW Mk1 8v cambelt tensioner might just do the trick.
Looking at this picture... I'm wondering now if a bigger pulley for the alternator might be available...
Purple Frog (Forum Supporter) said:Maybe the hive has a solution to my current problem...
The Raby 2300 has a 7000 redline. Unfortunately anytime I rev over about 5000 the monster throws off the fanbelt.
I've tried a few different belts with no success. I'm thinking the original '70s design never intended to spin the alternator that fast.
It sort of limits me to driving shorter distances (20-30 miles) during daylight hours. Just running on the battery only.
Any solutions out there?
If I understand the setup correctly from one of the earlier pictures in this thread the fan is driven directly off the end of the crank and the large diameter pulley mounted on the fan drives the alternator. Compared to other automotive applications that's a huge drive pulley so the belt speed must be pretty darn high. Ideally you'd reduce the drive pulley diameter to slow the belt speed down but that's going to be a challenge to fabricate and would close off the cooling fan intake (or is that the exhaust?). I'd look at a larger diameter deep groove pulley for the alternator. That would slow down the alternator, the belt wouldn't have to stay wrapped around the tight turn of the small alternator pulley and the deeper groove improves belt retention. Plus, depending on what that uses for an alternator you may be able to buy something off the shelf.
Purple Frog (Forum Supporter) said:Looking at this picture... I'm wondering now if a bigger pulley for the alternator might be available...
Something like a power steering pump pulley maybe?
If you're throwing belts, you've got a misalignment and or tension issue. Changing the alternator sheave (pulley) diameter to one larger will help prevent overrunning the alternator, but you can solve it without a size change.
Make sure the v-grooves are aligned. Watch this video...the challenge you have is that you don't have the adjustments you might need built into the mounting assembly. You may need to shim the alternator mounting in order to address the misalignment.
Reached out to 914 World forum, got some good ideas to follow through on.
I'll pass on here just for the record:
1. Some 914 racers soak the belt in oil so that it will slip on alternator during inertia changes instead of getting into a wild harmonic.
2. Belt should be 9.5 mm wide instead of 10mm wide so it will fall deeper into the "v'" of the pulleys.
3. Alternator alignment can be a big deal on older 411 engines since the brackets are sort of flimsy. OK at 4000 in 1971, not really up to the vibrations of 7000 rpm today.
The "oil the belt" idea might actually work in my application. Easiest to test in a hurry.
In reply to Purple Frog (Forum Supporter) :
Take a good look at number 3
not so much alignment as the bracket flex. On mine I one day discovered that my custom relocation brackets that shortened the belt by a several inches would flex. They were made from 1/2" aluminum so it was a shock to me that when I blipped the throttle with the hood open I saw the alternator move...and a shocking amount at that. Ended up using an additional bolt hole and gusseted the bracket to get it fixed. Now I can shake the entire car via the alternator if want to.
Great project!
Maybe also consider a guide for the belt. Its pretty east to fab something you can bolt on, then the belt can't fall off. You see chain guides on dirtbikes and mountain bikes all the time, no reason the same idea wouldn't keep a belt on. I use to have a 12 rib supercharger belt the wold skip a rib or 2 at high boost...a guide fixed it.
mke said:Great project!
Maybe also consider a guide for the belt. Its pretty east to fab something you can bolt on, then the belt can't fall off. You see chain guides on dirtbikes and mountain bikes all the time, no reason the same idea wouldn't keep a belt on. I use to have a 12 rib supercharger belt the wold skip a rib or 2 at high boost...a guide fixed it.
And the mad scientist makes a comment. And a good one at that
So I've spent a few hours on the interweb and can not find a source for a 9.5 x 965 v belt. (as suggested in above post)
100s of sources for 10 x 965. Many sites say the 10 is a replacement for the 9.5. Then, i get to wondering if .5 mm can make a difference. 
A Porsche restoration specialist nearby suggests finding a belt with cloth lining the "v" sort of like most lawn equipment belts. He also says its better to have a belt without the cogs inside.
Right now I'm driving downtown without a belt. I'll get back to the issue tomorrow. 
Its been so easy to drive around town without the alternator belt, that I just sort of ignored the problem. But a few weeks ago I decided to attack the issue again. Doing research at Samba and 914 forums I learned that the bottom pivot that mounts the alternator to the block is just a cheesy piece of bent sheetmetal, so it twists and distorts when reving engine beyond the original grocery-getter specs.
I took the offending piece off and did some welding and reinforcing with thicker mild steel and re-installed. Since then I've driven quite a bit with a belt that stays on and an alternator that is really charging the system. Seems possible to finally declare success.
This has turned out now to be a project car that gets driven often. It is more comfortable to drive in the cooler months since it has no A/C, and there is an engine 5" behind your shoulder blades with 1" of insulation.
We had fun with it at the Amelia Island Concours after the Lemons folks allowed us to park down the fairway saturday from the Radwood crowd. It was cool to cruise around Fernandina Beach doing brewery tours.
I also got off my wallet and installed TW300 tires. Testing it at vacant runways at St. Marys it impresses with the cornering G forces.
In reply to Purple Frog (Forum Supporter) :
That reminds me of how much of a sleeper your car is. When we first saw it we were like cool VW but then I found out you were there and looked it over more closely. That second look turned out into wow cool build.
Stampie, Great seeing you there, and David with all his "flashback" Radwood gear.
Its always fun to watch people walk by the bug and glance in the windows and they watch them do a double-take when they notice something "different" about the back seat.
So... Today I start getting text messages from folks all over....
"look at page 26" I get home, walk out to mailbox and there is the new issue of GRM.
And sure enough on page 26...
I'm sure I have David to thank for this. It made this 73 year old guy's day. Of course Mrs Frog is acting like its the Wall street Journal and telling everybody she knows...
Thank you GRM!
In reply to Purple Frog (Forum Supporter) :
It's a VW on a powered rollerskate that looks bone stock from the outside and will punch boy racers in the jimmy. Why wouldn't it be in the Mag?
This is great. How the hell did I miss this? Overall ethos of this thing is absolute hotrodder dream level.
Purple Frog said:First day of Spring Update.
The car is now street licensed and insured. I drive it on Sundays, and in North Florida the weather has been perfect for a car with no A/C. It is much closer to a purpose built race car than a daily driver. A blast to drive. Lets just say if you run over a dime on the pavement, you know it.
Since I have no speedometer, I just use a Garmin GPS on the windshield to know just how bad I'm breaking the law.
Figured out the gears (see chart). But, really not important, at about "110" the front gets scary light. Would need a serious front splitter to go any faster. The Raby dyno sheet sets the redline at 6500, I use 6000 to be safe...
Great car and project. I was waiting to hear how your car handled at top speed because I thought I remembered reading a VW drag racing magazine 50 years ago that said that they had to get through the quarter mile with as low an E.T. as possible and with a top speed of less than 112mph because the bugs would go airborne at that speed.
Thanks Purple Frog for taking some time to chat with us out at the $2000 challenge. This was such a cool build to see in person.
This is so cool, I've been seeing this car around for the last several years and never been able to chat with the owner.
I first noticed this a little bit into the pandemic out near Havana when I saw it leave a light, and I wasn't able to catch up in the other lane from a couple cars back, in spite of legitimately trying in my supercharged Miata. I decided not to break the law as much as would have been required to catch up.
I've seen the car a few other times as well, and have just never been able to chat with the owner. The poor '63 sunroof baja sitting on the side of the house will never live up to it's potential...
In reply to ToManyProjects :
He's very approachable once out of the car. My mom came to the Challange for her second time this year. She noticed it as she had a 70 when I was growing up so I took her over to look at it. He showed and explained to her everything about it and why it was so different from her 70. Good peeps.
Your mother is a class act!
Many thanks to Chris Tropea and J.A. Ackley. Real professionals. At the end of a long Challenge weekend they took the time to dig into my story and try to capture it. Since I know how much footage and camera shots they took, they did a great jo editing!
I know... it looks like a Georgia drug bust on I-95
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