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Newbee needing info on my Seth Thomas sidecar

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I am new here and yesteryday I waent to look at a 76 CB750, another buyer had just beat me to it. After talking to the owner he told me the buyer took the bike but had no use for the sidecar. I asked to see it and he lead me to the spot he had unloaded the day he bought the 750 8 yrs ago. We stuck a deal he said if I was interested in it he would help me load it up if I promissed not to bring it back, my kind of deal. I unloaded it today and was searching for some info, I have never seen one like it before. It has a sticker on it SETH THOMAS IND, LTD. 7411 Laurel Blvd, North Holly Wood,CA. Anyone know anything about it? Iwill be restoring it and installing it on a 77 GL1000. I seems complete except for ons bar.

Your sidecar reminds me of the units used in the Philippines as taxi's. There's a picture attached of the ones that are ALWAYS for sale on eBay.

BTW, The Seth Thomas Company [that made clocks] is a Connecticut company. The address you listed no longer exists according to Google maps but the closest building appears to be a row of small industrial suites.

Attached files

That things cool , I like the bumpers

Doug "Rain Man" Plotner 2nd Thief M/M chapter coordinator Eastern Panhandle WV USCA #8789 01 883C Sportster /Velorex combo 95 Ultra Classic Electra Glide /California Friendship combo Iron Butt Association member

Taxi is exactly what I'm thinking too. Concidering how menuverable a small sidecar rig can be, it would be ideal on crowded streets. As long as it isn't raining or snowing.

That's going to be pretty sharp when you get it restored!! Great barn find!

From what I have found out as of now, I found a mention of Seth Thomas on page 126 of Hal Kendalls book Sidecar 2003. I believe it was made in North Hollywood, CA as the decal states. I m still researching.

more pics

Looks like a real find, congratulations! I know nothing about its history but I do know a bit about the design which is excellent. Whoever designed it was intimately familiar with advanced low speed aerodynamics. This is shown by the slight rounding on the roof with a 'spoiler' behind it based on the Kamm Theory concept as applied to lift & downforce. Also the Kamm type spoiler would contribute the right downforce on hack rear wheel without so much force as to harm mileage. These few things would strongly contribute to stability at speeds above 45mp on into 200 mph.

The windsield rake is very good to match the other effects and angles, and the front bumper breaks the frontal airstream to prevent front lift under nose. The vents on sides [if used] are in precisely the right place, size and shape for excellent ventilation of the cab due to being in a low pressure area of the moving airstream. The front center vent is in exactly the right place and angle to take good advantage of that high pressure area to really flood the cab if it was opened up. Even the side fender is well thought out for aesthetics and airflow plus adding a nice retro influence.

These design cues would be typical of the late 60's to mid 70's. I would guess it was designed by an aeronautical engineer or aircraft designer and is likely very solidly built.


Thanks for the reply. I have always wanted a sidecar, but have a friend that keeps informing me of the cons of a sidecar. My game plan is to take my time in restoring the car. First I want to find out the history of it. While I m restoring the hack I M going to study as much as I can on operating a sidecar. I M going to try to make contact with other sidecars in my area to get first hand info. If possible find and take a course on operating a side car. Dose anyone know how to contact Hal Kendall the author of Sidecar 2003. He mentioned Seth Thomas in his book.

KrazyK - 10/29/2012 6:03 PM

Does anyone know how to contact Hal Kendall the author of Sidecar 2003. He mentioned Seth Thomas in his book.

Take a look here:

Lee / Summer Grove, Louisiana: Ural cT, CJ750, Burgman/Texas Ranger, Zuma 50F, MB5, TW200, CRF250L, GTV300

Sounds like you have a good plan there KrazyK!

I was somewhat surprised on another bike forum in their sidecar section to be told that I really shouldn't consider a sidecar for my ride. No, it would be far too difficult for me, dangerous, more than I could handle and far beyond my abilities now or in the future. Right. But somehow with their superior knowledge, wisdom, cleverness and natural gifts it was no problem at all for them of course. Hmmmm, Really? That special at birth?

Go for it! No reason in the world you can't have a great ride going there. I know I'm going to ha! That's a great looking rig to start with too. Enjoy yourself sensibly and responsibly, that's the main thing.

Hope you don't mind some lengthy notes about the fascinating design. Just can't help myself because it's such an outstanding invention. I'll start from scratch, in case anyone is interested: Looking at the side view the front & windshield would be a high pressure area as car travels. Air is forced up windshield and over top at high speed and high pressure. Windshield slant helps lower resistance and coaxes air rearward.

If you stood the car on back end and looked at the roof's profile you'd see that it's very similar to the throat of a carburetor viewed in cutaway, for good reason. That air whipping up over top is accelerated. Another airflow [secondary depending on who you ask] is above that as the car travels through space, forcing that windshield-to-roof air down and tightly across top.

Roof air flows across that rising rounded section, like the venutri of a carb throat, which further accelerates that air mass, speeds it up as if it was passing through a narrowed pipe, like a nozzle. The other secondary flow at high pressure above the air at roof top forces roof flow down, where top contour takes a dip downward after gentle upward hump. That roof air spreads out and becomes slightly more negative pressure, lowering resistance and in effect pulling the incoming air over roof as air speed is artificially increased.

Next this roof airflow suddenly hits the 'Kamm Effect' spoiler at rear. This accelerates it upward to the highest speed yet in its flow, and faster than the secondary airflow up above car in space. The secondary airflow then hits that upward moving air mass and forces it downward without much loss of velocity or air mass. That makes the Kamm spoiler air roll over and curl in a C shape, down behind sidecar, and causes that airflow to curl over to push against rear window, accelerating car for free: push-me pull-you! That's why it has a large flat rear instead of a rounded contour. At the same time the Kamm spoiler forces rear hull downwards for better rear traction.

That's not all. At bottom surface of car it's designed like an early 3 point hydroplane. The lowest front section becomes like air pontoons as air flows under, causing a slight frontal lift. That's also a venturi effect, as increasing air speed. However windshield/roof airflow is also keeping positive pressure downward on car at same time, to help stabilize against that slight frontal lift, balancing out the effects. Then behind pontoons the underbody suddenly tucks quickly upward and that becomes a low pressure area, pulling the moving air in as it expands. This further speeds airflow by lowered resistance as air travels under car toward rear. Underbody contour rises more and more until air spills off bottom and meets the top's air column that pushed against rear window. The bottom airflow helps pull that pushing-force flow away to behind chair, so there's more room for Kamm Effect positive pressure airflow [and more push] and even less resistance to it!

In addition the final low pressure air behind pontoons pulls entire car down toward road as Kamm effect air also pushes it down to combine their effects to stabilize the entire hull and help force wheel traction toward road surface giving better grip as mentioned above.

I believe the hull was designed to have full doors and slanted clear plastic headlight covers to help the airflow behave as intended. Because of where the front round air vents are and locations of side vents in rear [if they were all open] it would have very positive airflow through cabin without detracting from all the rest. That venting system would be a great benefit if it did have full doors. That is without doubt one simply amazing design. I'd say a professional aeronautical designer for sure. Cool machine!

Thanks for the info. I have the frame on a table now. I am going to build a new frame. an exact copy as there is some metal fatigue. I took it to work a had one of the engineers plot it, now I have a set of plans.

Sounds great, KrazyK!

I hope that last post wasn't out of hand. It's just that as I looked at it a second and third time and started to analyze the design in greater depth I ended up in jaw drop amazement over the details. Not obvious to the casual observer and the only reason I saw it is because of years of interest in the subject.

Best to you in your rebuild!

XLerate, that post was well written and as a non engineering type I could follow it and understand it. Thanks.

Wolfhound - 12/1/2012 5:35 PM

XLerate, that post was well written and as a non engineering type I could follow it and understand it. Thanks.

Thank you, Wolfhound! That's just what I hoped for.

No it was not out of line. It was very informative, well written and easy to understand. It inspired me even more. One of the guys suggested I cut it here change this or that. A few of the guys at the shop thought it was ugly. A couple said they would not be caught dead in it but Norma said she would ride in it any time. Me I want to take it to the wind tunnel the next time we test.

Restore it just as it is. It is an example of perfect engineering and once restored it will last you forever. Plus you can load a
lot of groceries and stuff in it and use it as a Taxi if things get worse economically!

Wolfhound - 12/1/2012 8:35 PM

XLerate, that post was well written and as a non engineering type I could follow it and understand it. Thanks.

Same here! Thank you!

That is a great find. Looking forward to your progress with the restoration.

Wel, thanks very much, folks!

KrazyK, that would be just fabulous if you can get it in a wind tunnel! I'm sure the results will be very interesting. Just had a little disagreement with some other folks on the net over Dr. Kamm's theories so even today the future is being made as the past is learned from. Can't wait to see your finished result, and good for Norma, she sounds like a real 'Keeper' too! You are indeed fortunate...

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