Old Guys Simplex moto-peddle bike

culvercityclassic said:

I like it, looks like in the picture the motor fits in the frame? Maybe I am not seeing everything. Really like the fork, you got yourself a nice project going on Rick...

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Thanks it almost fits & my photos are mostly third rate on a good day. The fork will end up being a girder re-enforced springer, not ruling out the use of dampening on rebound if it's required.

Your build is progressing so well. Can't say I'd change a single thing about it except the address when it's finished. I could find room for her in my stable of bikes.

I've been studying the double down tube Helmut frame as a candidate for a frame to be used in a future V-twin build I'm considering. I need to gather some specific info on frame dimensions to mount a Yamaha 250 cc V Star twin (100 lbs. total engine weight). The frame looks strong & might not need much if any additional strength. Be great if no cutting was necessary for fit.

Rick C.

Hi butch, It is a Simplex fork that I'll be modifying a bit. It's a 1" steer tube cut off at exactly 6". I've never seen one used on any motorized bike builds before. Really don't know why cause they are definitely vintage. Heavy duty legs, rockers & springs were used. Wayne M. the Simplex guy has the replacement springs in chrome. They really do look similar to some of the early Harley springer forks. Hope this helps. Rick C.

Good idea Ludwig.

butchl said:

I know Wayne, see him at Portland meet every year. Good guy. I always worry about using regular bicycle head tube. They just don't seem thick walled enough.

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Butch my favorite bicycles are the Mountain variety & I built my personal Mountain bike about three years ago: full suspension, air over air, custom fabricated aluminum frame etc. etc. about $3,000. in parts alone. Same frame from the same custom shop was used in the Red Bull rampage a couple of years earlier so it was an "outdated design" for top competition & I got it for a fraction original "cost". When I received it I was concerned about the head tube/neck...seemed flimsy to me yet I'd played several past years of the rampage competition & those guys are totally insane! Drops of twenty to thirty feet are not even seen as great obstacles. Jumps are measured in yards now. Materials & fab techniques used on quality frames are so past the twentieth century bikes. I also don't worry about frames built of DOM tubing. I've used .090 wall 1" tube in race car frames that survived significant crashes with remarkably little damage, never really trusted it to save my life, but I do now.

The shipping weight on Pat's Flyer frame was about 18 lbs. well packed. Let's say 15 lbs. that's really heavy compared to even a mountain bike frame, but super light when compared to my Copper Gator Simplex at over 30 lbs. That frame is way overbuilt (also using DOM steel) for the weight and power the CG 125 puts out & I'll probably wear bearings out in the bicycle hubs at a faster rate as a result.

Bottom line in my opinion is, for a daily rider, not intended for racing or wheelies or demolition derbies; quality bicycle frames, and that includes the neck & head tube, are more than strong enough.

That brings me to the antique Simplex fork. It's in really good shape, but it's almost 60 years old and not made of modern steel alloys. It wasn't welded using a square wave tig & 70,000 lb. filler rod either. So as a precaution I will be reinforcing the fork steer tube and any other suspect area. I see this as the most suspect "weak" area in the fork/frame connection.

I will be cutting the frame down tube just below the lower straddle tube to change the angle of the down tube, allowing a more forward mounting position of the motor. It appears I'll need about a 4" increase to completely clear the bottom bracket and the 25 tooth pedal drive sprocket. I'll add a small gusset plate at the junction point of the down tube splice for added support for the new connection. I dislike altering the line of the Flyer's lovely down tube, but it's quite necessary, as I don't want to weld in the brazed area of the head tube. Pat tig welds the lower straddle tube to the down tube so I'm more comfortable making my splice & adding heat in that area.

Hope this somewhat clarify's my thoughts about the frame to fork connection.

Rick C.

Fun times indeed Butch & so are these...just different.

Woke up early and started thinking while drinking (coffee) I'd looked up some information regarding the relative weight of the industrial clone engines (160 cc) & the motorcycle clone variety (CG 125) I used published shipping weights and deducted a few pounds to come up with a rough estimate of dry weight. I'll put in a disclaimer at this point. I'm a fan of both types in varying displacement sizes. Both build out & perform really well. I've used the industrial in multiple go-cart builds back in the day but never on a bike 'cause of a bad Shoulder (rotor cuff) today I don't own a pull start engine...not even a lawn mower, but only because of the shoulder.

Here's what I came up with CG 125 cc, speed & wet clutch, kick start...55 lbs. dry weight. Add 20 lbs for electric start & battery (lead)....75 lbs. total weight.

GX/GC 160, pull start only 25 lbs., Bully clutch 5 lbs., electric start & lead battery 20 lbs. Total weight 50 lbs.

I can't see that the weights of either base engine, 30 lbs. for the industrial clone with Bully clutch or 55 lbs for the CG motorcycle clone with kick start is a problem on a decent frame. The GC with electric is almost the same as the base CG weight so no problem there either. Of course a well designed & installed motor mount is essential to distribute the increased weight & engine torque or even the best of frames could be damaged.

When all is said and done rider weight is just as much of a problem as added weight anywhere in the build. The rules of physics still apply. Big guys put a lot of strain on a bicycle frame motorized or not & this weight needs to be plugged into the equation as well as any additional accessorized weight load.

Un sprung weight factors in pound for pound as more of a problem than sprung weight as well. A good front suspension helps protect the frame as well as the rider. Larger & softer tires help as well. I have a bike that rolls on 24" x 3" tires front and rear, no suspension front or rear that rides like a dream cushioned only by the over sized tires.

A lot of stress is also delivered to the rear triangle on board track builds as a result of our using (yes I'm also guilty) the rear seat stays for primary support of the back side of the boardie racing saddle. I love the look & I've not yet cracked a stay, but I've broken a couple of brackets over the years and confess to almost going down as a result. I was lucky. My brackets have been radically beefed up, but I now wonder what's become the weak link at this point. Now, on frames with a traditional seat tubes, I always utilize what has historically worked best on bicycles. Tube in tube, even on board trackers. I feel it lessens the damaging loads on the frame more than increased engine weight.

In the same vein: use the pedals to support at least a portion of your weight, especially if your a big guy. That's one of the most important reasons bicycles have pedals. Yes you can power & start some of the motors with them & set the coaster brake as well, but keeping some of your body weight on the pedals lessens the shock delivered to not only your spine but also to the bikes frame and components. The strongest area of a good bike frame is the bottom bracket. Directing a good portion of your weight to the bottom bracket lessens the shock to more vulnerable areas of the frame. If you put all weight on the saddle & hit a bump your weight is multiplied by the momentum created and sent directly to the frame. Your legs bearing weight act as springs and rebound control when riding on rough roads. I realize that some are not physically able to bear much weight on the legs. For these a well sprung saddle attached to the seat tube will modify and direct the forces down the tube to the strongest point of the frame, again the bottom bracket. Not as effective as using the legs but better than directing the force to the rear stays.

Thinkin' & drinking...not always very helpful, but I try.

Rick C.

I spent the early morning hours reviewing 1920's thru 1930"s Harley D. forks styles and variations. It's amazing how many great and small changes were introduced in forks even in the same year and model HD. Rigid, single spring, dual spring , large spring & small, girders of all shapes and sizes. Rockers, tube sizes and decorative bracing deviations, makes me think they kinda let the line worker use what material was at hand to build a fork as he determined. Anyway I've got a mental image of what a Harley Davidson fork looked like over a period of two decades & I've a design in mind that will be, I hope, representative of that twenty year era. Having a Simplex fork as a base I'll stick with the dual small diameter springs & the cast rockers, but add a girder to the rearward legs that triangulate from the top of the legs to about 3" above the rocker pivot point. In order to clear the front leg the girders will orient at a slight angle to the outside of each fork leg. I'll add additional back leg bracing under the existing brace on the Simplex as well. Steer tube reinforced at the cross bracing as well. The headlight bracket will be either shortened or removed altogether. I also have some thoughts as to decorative embellishment, minor but distinctive.

Rick C.

Butch I'll be modeling the fork girders soon. To see exactly how the Simplex fork will look with girders & will post some photos as well. I'll also decide if I'll cover the springs with a tube or not. At this time I favor exposed springs with an extended brass or copper spring "towers" but I'm open to change. I've neglected asking Simplex owners how the stock springs ride especially on bikes with higher powered retrofitted motors. Need to do that as I've never ridden a Simplex with factory forks. Guess I, shamefully put the cart before the horse on this one, but the forks just look so cool to me!

Rick C.

The Simplex guys gave me a good report on the smooth ride of the Simplex fork & a couple of tips on improvement. I don't expect air ride quality at any rate, though I'm being spoiled by the air shock saddle on the Simplex Copper Gator. It's a real ride game changer for any hard tail bike!

I could accurately claim that progress is being held up by lack of parts but I'm using the time to study and weigh options in several areas. Small details that could make a major difference. Getting wheels under it will be the starting point and I should have the headset by this weekend & can assemble a "roller" then measure the amount of "trail" this fork & frame combo delivers & total length axle to axle...both important to riding stability. I think were golden here but I'd rather not be surprised later.

Rick C.

Simplex Copper Gator's officially broken in (my scale) with 30 plus hours of gentle all purpose riding. 3 oil changes and no drama. Rick C.

Thanks guys. Got some old (both fronts) wheels under the Peashooter along with a pair of mismatched tires. Installed the headset first of course. Wheelbase 49.5" & fork trail 2.5" should be pretty stable at reasonable speeds.

The front tire is a new Fat Franks "Thick brick" & stands 27.5" I really like the look on the Simplex fork with the black rim (Wally world junk). I'd been thinking about using black rims on this one and I'm now convinced enough to order wide Black steel rims, Sturmy drum front and coaster rear, along with 10 gauge stainless spokes. I'm tempted to order another Thick Brick tire as well for the rear...sure fills up that fork nicely. They are only 2.235" but stand so tall that they appear wider, especially on wide rims. I don't want wide tires for this build but I do like the extra height. I'll compare with the Vee Nola's 2.5" which stand about the same height but have almost 3 times more load rating and much stiffer sidewall.

Loop is 7" off the ground so a 3" drop with the "Keystone" will yield the same 4" clearance I have with the "Simplex Copper Gator" & I've no problem clearing the monster school zone speed bumps we have here. Also have enough clearance between the down tube & front tire to bend the down tube 2.5" to 3" forward to gain the space needed to properly mount the CG 125 5 speed engine.

How I see things at this point are of course subject to change but think I'm fairly close on the basic design elements required to make the Peashooter Harley appear to be from the board track/flat track racing transition era. Where men were men and women were glad of it!

Rick C.