Gracie's Hack... DR650 sidewalk chalk build

**Edited** to include new upper subframe. I decided to leave pics of the old one for reference. New pictures in post below

I've never built a sidecar before and am going to need some advice and info. I got most of the subframe mocked up and thought I'd start a thread to get some feedback/criticism. The blue tape is where further bracing will be added. The real questions I have are in regards to the strength of my mounting points. I'm confident I can build a nice frame and car, but if my mounts aren't strong enough and in a decent location for geometry it will all be wasted. Please tell me if you think my frame mounts (specifically my uppers) are going to last in the long run and not ruin my bikes frame.

This is Gracie and she is moping while she thinks about the wind in her face and the freedom of the moto...



I use sidewalk chalk for fabrication all the time. This is my idea of the car frame (will likely change/refine). I was originally thinking 2'x4' for the frame, but am worried it may be too narrow. I want narrow for offroad riding, but not too narrow negating the utility. It will also be built from 1.75" .120 wall tubing and will basically be a flatbed that a car body can be bolted to for Gracie. Construction of the frame seems easy to me, I'm just trying to hash out the size before bending the tube. I'm thinking I may keep it 2x4' and just space it away from the bike a little to leave room for my upper control arms without compromising car space.



The swing arm and tire/wheel combo are in process. I was planning on building a custom swing arm and machining and axle and such for a spare DR wheel I have (would be nice to have matching wheels), but am now thinking I may cheap out and be lazy with a trailer hub/wheel combo swing arm. Depending how I like it I may spring for air suspension (many options here) or keep it simple with a moto shock. Chalk drawing hasn't yet accounted for wheel placement and swing arm dimensions.



I am so close to bending up the frame and am having a hard time waiting for feedback so please give me your thoughts and advice. I will try to curb my stubborn attitude to listen to experience.

I would love to see some links to photos of trailer hub swing arms. Maybe even a few custom two-sided swing arm setups. I really don't mind having a swing arm visible from the side of the car.

This is going to be good!

wow...
looking forward to this one
thanks for taking us along on the ride

This thread will become a regular stop over...
With the the way you have made the sub frame
it would have been easy to move the rear mount
fearther rear-wards...wider spaceing would have
given more ridgillity in the mounts..
Thats possably a mistake I made with my XR build...

Structurally it should work fine. The three load points to the external world are triangulated just fine.

Don

Hey guys--unfortunately, this is starting to look suspiciously like a BUILD thread. I'm notifying AceRph. Build threads are not allowed here anymore.

I think the OP is seeking sidecar specific advice which he may not get in the build thread

Agreed! Can we move it to the build thread when I don't need help anymore??

Anything to say about the car frame size? What dimensions might yours have? Info and/or pics on swing arms? I am searching and reading plenty in conjunction with these questions, just looking for some specific info that is easier to ask about directly.

I didn't get my TRIANGLE right when I built mine and it works GREAT,lots of offroad and it's a heavy car and it's holding up great.NEXT build I will get it right but for now it's working great.

Hey! I just realised something. You're mounting the sidecar on the left hand side!

Oh, and a few pics.

Single sided swingarm detail



Sidecar Chassis detail:

it looks like you are planning a Left side mount?

Yep, left side mount. That's not a problem right? I know that right sided mounts are more common and "correct" for the states, but I like the fit and function of the left side.

What's the legality of that caveboy?

Here in Aus. it's like a left and right hand drive car.

not a problem if you don't mind not being able to see around traffic without putting your sidecar into the opposing lane. If it is strictly an offroad rig it won't make any difference. If it will be on the street it is a bad idea unless there is a compelling functional reason to set it up that way. The only thing that comes to mind is rural mail delivery

Ok, turns out I'm not as stubborn as I thought and I'm easily persuaded to change plans and priorities. I didn't want to put the car on the right because I had a stronger and much much easier mounting system on the left side. After pondering the traffic topic I decided to get my head in the game and make it work. Here is what I came up with. What do you think? I also spaced out the lower mounts a little more as mentioned above. Thanks for the comments... please keep them coming.

Lower sub frame is 1.75" .120 wall and the upper 1.25" .120 tubing. Lower rear mount will be braced but didn't get to that today.



She is ready! Turns out I don't work fast enough for her. Frame is 1.75" .120 tubing. Track width should work out to around 44-45". Good??



This is the mount in question. It is behind the oil cooler and only uses that one oil cooler bolt. The bars in the first picture that tie the whole "upper" frame together are only there to give this mount longitudinal and vertical support. I believe it will be strong enough, but don't really know about the forces involved with moderate offroading of a sidecar. Please weigh in... especially if you are a sidecar builder!

Yes... It dose look small in the pic light bracket "8mm bolt?"..
Is there any chance of going up with a 5/16" 8mm plate between the tank & frame?
then bolting though the gusset at the steering head back bone juntion ?

Looks like you have a great start. I'm hoping to start on a DR650 based rig this winter.

Now that we know your not going to be shuttled to some obscure sticky let me say this...

I like your approach, haven't seen the chaulk board slab layout technique in years, looks like a boilermaker shop.

You have great skills it's evident in your fittings so far.

Go wider on the bottom mounts, say 2/3 the length of the chassis you made. Keep everything at least as high as the lowest part of the bikes chassis.
Go wider at the top, get up at the neck if you can and take the rear up to where the top of a twin shock would be if you had them.
Think about how aero engineers design and attach a wing to a fuselage.

44 inches is not a bad width for an off roader. Stable enough and it should leave you a good 12" for your right boot and leg,
you want a little wiggle room there.

Glad you decided to put the car curbside. With the crown of most roads it would be odd to keep the chair on the highside of the pavement,
not to mention putting your passenger or load out into the opposing flow.

Be prepared to stiffen up that shock, no mushy mushy wallow needed.
You are building an asymmetrical tractor.


Don in Nipomo

I am waiting to see how you do this.

Don in Kalifornia

These are some interesting challenges. I am going to have a hard time accomplishing all of them, but will see what I can come up with. I'm a little worried about the motorcycle's frame strength and attaching the diagonal support to the rear of the bike as suggested (bikes tail sub-frame). I have a couple attachment points where I have the cargo tail rack, but the frame there is small diameter and wouldn't seem to take much of a lateral load. I could be wrong. I'll see what I can come up with.

I would like to keep the ground clearance decent so will also look into side car frame height in comparison with the bike's frame clearance.

I found some info from another DR650 car that I believe had DMC mounts and the guy was breaking that oil cooler bolt. The DMC mount is a little different than my contraption, but I am still concerned about that mounting point. I will have to see if there is a decent way to strengthen that mount without it being "hack". I'm sure it would be fine with normal road vibration and stress, but logging roads and washboard vibration may take its toll.

Thanks for the help and yes happy to not be an "obscure sticky". Please keep the comments coming. I know some of you fabricators and sidecar builders have things to say. I may have to take a day and work on the car body for something a little different until I've gotten enough feedback to feel comfortable moving forward with the frame attachment/design.