Featured Project - Herb Hartman's 1991 Cadillac DeVille

Featured Project of the Month for July 2015 is Herb’s 91 Caddy. This is the one you might have seen on the evening news!

“I became a member of DOW about the same time Wayne started posting the construction videos and have been working on this ever since. I went out looking for a Dakota and came home with a 91 Caddy…This is a dual system all the way, from the dual combustion intake air inlets in bottom of lower drum to the one butterfly that lets woodgas into the 4.9 engine.”

[Premium members can view the full build thread here: Wood Powered Caddy]

Herb, if you could update us on the status of the Caddy, we’d be grateful. Great work!!


O Thanks, I will update, right now I have the fire tube out of it just looking things over and “I think” improving a few things. Had some stress cracks on the bottom lid that holds the fire tube and in general “lovin” things up a little. Should have it back together next week and would be glad to post some pics and maybe a video! Herb H


HI HERB HARTMAN,thats a nice looking build on the caddy,I bet you get better than one point 3 miles a pound, And how did you happen too get on the news.THANKS

Hey Kevin, I don’t know what it gets per mile, depends, depends, depends! I’ve really never tried to keep track of it, when the hopper temp gets up around 400 I put more wood in it!

I was listening to a radio talk show and the subject of woodgas came up, a few people that called in had there story about seeing some pickup on woodgas going thru town and no one really knew about it. Latter that day I sent a email to that radio station about having a caddy that DOW and a few weeks latter channel 13 news called and asked" just tell me this, do you have some kind of car that runs on wood?" I told him all about it and they came out and did that vid a couple weeks latter! They did a couple hrs of filming but had to cut it down to fit on the 10:00 news, that was a blast doing that!


Gettin Caddy back together slowly, found some rusted thur places in that lower section, the outer jacket was questionably thin when I first put it together three years and 5,000 miles ago so I replaced the lower 2 ins. of that. The 1&1/2 flex tube I used for combustion air was full of pin holes and some of it missing, replaced that, the material I used to connect lower drum to coolers (8" stove pipe) was rusted to thin to reuse, replaced it. It had to set from the time channel 13 news did that story last year till now so I’ve got a feeling that’s when it did most of the rusting rather then while it was being driven. I knew I used thin Matt trying to keep it light so I was kind of expecting some rusted thur places! I did get the lower section back in there today and took a few pics while putting it back.

I guess my pics are to big to load! Maybe latter! Herb H


Sorry for the rust Herb. I think setting around is hard on things and people. I guess that’s why SS is so good. Hope you get it going soon.

Yeah thanks Carl, I know you know about rust, my barrels didn’t have any holes in them though like yours did, mine was just where I used super thin metal and where it gets the hottest. If I remenber right your hopper went first! What’s your opinion on what made it do that, that’s different then what I experienced!
How is yours doing now after the rebuild and how are your thermocouples hanging in there?

Hi Herb, If corrosion is a problem, be it rust or acid, I see 3 answers. 1)Thicker material will last longer, thin ANYWHERE is problematic. I think the vibration of a “rumbling muffler” plus moisture (rust), contributed to the failure there. 2) Find, fix/remove the source, haven’t had much luck there, or 3) Go to SS. I’m still not sure why my wood hoppers are being eaten alive. Evidently more (concentrated) acid then most folks. My percentage of oak is way down now, but the hopper is still getting thin. The next one will be SS. Two sides of the lower gutter are already SS.


Got the Caddy back together, put the char back in it, lite it and put about 10 gal of fuel in it. I let the fans pull air thru it for a while and lite the flair, took right off! Dicided to take it for a ride, started on gas and changed over to wood soon after that as usual. Took it outside of town a ways, turned around and went thru town and out the other way and on the way back in bout the time I was thinking this thing is running great it blow every pop-off on it! I switched over to gas and drove it home. This morning I checked things out and discovered it was out of fuel, it was bout 4ins. below nozzles!
Will that cause them to blow? Of course it’s still pulling in air and if there’s not enough wood I guess the air with the gas that’s in coolers and filters could explode! Suppose that’s what happened? Couldnt believe it was out of wood already although I know they will use more wood then normal first run!

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Glad you got her back together Herb. I can’t help you with your question. I have not started the other 75%:but I would guess that was the cause, lots of air space with no wood in the hopper and the mixture is right

Hi Herb,
That is an elegant looking caddy, showroom quality. That rear view shows an interesting configuration. I used line D imbert dimensions to build my stand alone unit. Two of your statements struck me as items I have just experienced. I’m starting to time my burns and taking temps in 4 locations and trying to find out when to add fuel. I have gauges for preheat temp, burner shell exit gas temp, cyclone exit gas temp and cooler exit gas temp. I don’t have a temperature gauge in my hopper. My first run burned down to the restriction! Hmmm? Too late! I know a new load of wood cools the hopper initially, so the temp then rises as the burn progresses and at 400 degrees you refill. Where about in the hopper have you placed your temp gauge? I think this might help answer my refill question (monitor the hopper temp). I was looking for something to indicate feeding time.
Is the stainless steel area insulated? If so, what did you use and how thick.
Thanks for the post, Herb, DOW.

Good morning brother Herb.

Sorry to hear about the pop-off :disappointed:

It seems that when building a new charbed or after a charbed has been disturbed the gasifier will use 3-4 times the amount of wood .

I am not sure the low char could have caused the pop but we know you were making gas :grinning:

Should have gotten some high temp reading at the cooling rails and hopper .

Thanks for reply Jim, Pepe and Wayne!
Pepe, down to the restriction, I thought mine was low on fuel!
My temp gage is about half way up hopper, it’s always been pretty dependable, when it gets to bout 400 it’s pretty well out of fuel, I just wasn’t watching it close enough, somewhere between being thrilled that it was running again and figuring I still had plenty fuel I didn’t think about checking gages, that big BANG woke me up real good, seems like the car blew up off the hiway about 2 feet, everything shook, I looked to make sure there wasn’t anyone behind and checked for flying debreh on the road, switched over to gas and went home! It was good gas alright Wayne!
As far as insulation behind the SS Pepe the only place I have insulation is in the bottom barrel, at least i used to have until this last Bang! hehehe
Herb H

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So THAT is the “Big Ban Theory”. You run out of wood. People have been talking about the Big Bang Theory and now we know how the world was formed. Herb’s gasifier in another time.TomC

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glad to hear your on the road again herb . I do get a backfire at the intake If my hopper is low and I think I can make it to where I gots to go.

Thanks, Herb, I was thinking that would be a good start. I’ll install it and burn some more wood and shut down at 400 degrees and see where the fuel level is.

Glad you’re going again Herb. Problems are a headache though. A clean out is always an unknown for me. Sometimes it’s like I never toughed it, and other times it’s like demon possessed! I’m sure you’ll get it, because “she” is your creation. Good luck.

Dang if it didn’t do it again, this time I had just lite it, got a nice burntube of red hot char, put in enough fuel to bring it up above nozzles, shut puller fans off and just let it brun up thru the hopper to gain some char and then I was going to put fresh fuel in it and go for a hide! After the flame started coming up thru the hopper real good she let go! BANG! It bent all my spring loaded doors again not to mention scaring the HELL out of me!
I’ve got it backed into my now AC shop and going to go over it with a fine tooth comb! I figure it must be pulling in some air someplace or it wouldn’t have that potent mixture, I probably forgot to put a plug in somewhere or something else stupid, stay turned , still learning! Herb H


You said you shut off the puller blowers. Then you let it burn. With the puller blowers shut off the smoke ( gases) go up into the hopper. If the lid is down, you are just about guaranteed a sneeze. The gases mix with the air that was let in while the lid was open. When the “right” blend of gas and air is reached and you have the fire, it ignites. Mine will give a sneeze even when I keep my puller blowers running, if I open the lid and don’t fill it clear to the top with wood to take up the air space.TomC

Yeah Tom that’s right, that has also been my experience but I was still in fill mode with the lid wide open when it blow! I’ve never had that happen before!! It has to be pulling in air/oxygen somewhere for it to do that!