View Full Version : Pat

06-23-2009, 03:12 PM
Lately I have been building a Pedal Assist Trailer. It is a one wheel push trailer which can support a lot of different motors. I have them with a 350 using a scooter wheel and fast scooter sprocket. I also have one using a 450 watt motor and a 16" bike wheel.

How to build a pat
How to build an inexpensive two speed emotor bike. The story begins with the search for a wheel.

Now I usually use a scooter rear wheel with the motor bracket attached. But for this build I am trying to go for the easy to find, anyone can do it, build instructions. So I have decided to use a wheel from a child's 16 inch bike. The thrift store had one for eight bucks but I wanted to see if I could find one for a better price.

Donar bike

step one
strip donor bike

First you will probably need to remove the chain guard. Cheap plastic headed for the land fill. Mine was held on with a couple of Phillips screws.

Then you will need to loosen the bolts holding the rear wheel on. I found a couple of dropout locks as well. You might need to completely remove the bolts and any other hardware holding the rear wheel in place. Remove the brake lever clamp so that the wheel will move freely.

Move the wheel in the drop out slots until the chain is loose. Work the wheel out of the drop outs.

At this point it should look like this....http://i44.tinypic.com/14e0uja.jpg

Next you should remove the brake lever... at that point you wheel will look like this..http://i42.tinypic.com/xknl8h.jpg

Use your chain breaker to push out one of the rivets in the chain. I push mine ten half turns and then twist the chain. This should leave the rivet hanging so that you can use it to reuse that chain later.

At this point you can toss the rest of the bike if you want to. I however always junk it out as much as possible. For instance on twenty inch bikes and up the cranks are mostly interchangeable. Why would you want to? On a motor bike pedaling is secondary. The shorter pedal arms make it much more convenient for me. However on a sixteen inch bike they usually are not interchangeable so I didn't bother.

I pulled the handlebars and the goose neck from the bike. Those high rise handle bars are good to use if you need to sit low on the bike for balance and your knees hit on a regular handlebar. Mine always hit on a mountain bike it seems. I also pull the front wheel since the spare tire and tube are good to have around. It's easier to pull the whole thing than to remove the tire. I also pull the seat and post. The seat is too small for sure but the mounting hardware under the seat is pretty universal.

At this point I put the frame out for the metal junkers to pickup. If I still drove I might take it to the crusher myself. I expect doing that you can more than repay yourself for the purchase of a donar. For instance the rear wheel is about thirty bucks. The chain is over five... The front wheel is probably the same. You also have the equivalent of one new tire (between the front and rear ones) and a couple of good tubes if you are lucky. The seat hardware and handlebars are worth something down the road. In other words it was a good buy so far.

I shot this before I added the handlebars and goose neck to my stash.


06-23-2009, 03:18 PM
welcome deacon and people deacon is the master of innovation. i have seen a lot of his projects and they are awesome. glad to have you with us deacon

06-23-2009, 03:31 PM
Step two is to buy a motor.

So most likely you will wind up with a scooter motor. The are almost perfect for building pusher bikes. They come in all kinds of power and mounting configurations. I will show you how to build with a currie motor scooter motor. It looks like this. NEW IZIP 500 24VOLT ELECTRIC SCOOTER MOTOR/ PARTS - eBay (item 320386087798 end time Jun-25-09 15:21:34 PDT) (http://cgi.ebay.com/NEW-IZIP-500-24VOLT-ELECTRIC-SCOOTER-MOTOR-PARTS_W0QQitemZ320386087798QQcmdZViewItemQQptZLH_D efaultDomain_0?hash=item4a987fbb76&_trksid=p3286.c0.m14&_trkparms=65%3A12|66%3A2|39%3A1|72%3A1205|240%3A13 18|301%3A1|293%3A2|294%3A50)]I build exclusively with motors of this configuration. The come from 200 watts to 1200 watts. I have built with the 250 350 and 450. The more watts the more power. Also the more watts the more expensive. I also always build with 24 volts. I don't like the expense and weight of more batteries but that's just me.

Step three is a decision... the motor and the bike wheel have mismatched sprockets. You can put a bike sprocket on the motor or a scooter sprocket on the wheel. I chose to risk the $5 wheel rather than my $35 motor.

I bought a small scooter sprocket from TNC scooter store. I got a 55 tooth sprocket but you can get others. I welded mine to the sprocket on the bike. If you don't have access to a welder, or a friend with one, you can always find a shop to do it or you can drill and bolt the new sprocket on. If you just use your imagination you will have a rear wheel that looks like this....http://i40.tinypic.com/qqv9k7.jpg this next one is a not so good picture of the rear of the sprocket which is where I welded it. Oh yeah be sure it is centered..http://i44.tinypic.com/wmgisp.jpg


You can use a the bike bracket from TNC scooters to mount the motor onto the wheel axle. I had a mount bracket that I was already using on the bike so I kept it. Mounting th motor should not be a problem.

Use your imagination and it shouldn't be much of a job to make a unit with motor and wheel on the axle.

06-23-2009, 03:33 PM

To manage step five you have to build a trailer frame. Again welding is better but you certainly can bold this frame together. The pusher wheel is actually a bob tail trailer.

so to build one you need to make two side rails. One end attaches to the bike and one to the axle of your rear wheel. The rails are best left without a connection between them. It is easier to remove the wheel if you can just remove the whole rail. So this is what you need to build.

You need two of those.... You can build exactly like that or better depending on what you have laying around the shop.


How long should it be.... as long as necessary. It needs to be at least (half the size of there rear bike wheel + half the size of the pusher wheel+ two inches) that is bike axle to pusher axle hole. You probably want some excess tail. (No crude remarks please)

What should I use for the sides. I used square tubing for the one you see but I have also used the solid L channel pieces from Home depot.

How do I attach it to the bike. However you can. There are usually some holes around the rear axle of the bike to use for attaching. I usually attach most metal to the bike so that I can work with it separately from the trailer.

What are those L brackets on top of the frame. If you look at the picture of my pusher you will see that I put the batteries right onto the pusher. The L brackets are what I use to hold them.

Now at this point you should have the pusher attached to the bike. Congrats you are almost finished.

06-23-2009, 03:35 PM
step six

the last thing to do is to wire the bike up. I use an on off on switch it give me a two speed helper motor. One that steps right out there.http://i41.tinypic.com/2eyytza.jpg

the diagram is easy to follow you have the negative wire of the motor going to the negative terminal of one battery. The positive wire from the motor goes to the center terminal of the switch.

One wire goes from each of the end terminals on the switch to one of the positive battery terminals. Then the last wire goes from the unused negative battery terminal to the positive terminal on the OTHER battery. If you get it right your switch will provide half power for starting from a stop to full power to running.

Be sure to wire in a fuse. A 40a will not melt the wires and give you some protection... You can try a thirty but it might blow.

Good luck you are ready to roll.... Please be careful it takes a little getting used to, but it is a nice, easy, little DIY ebike.

06-23-2009, 04:09 PM
Lest you think I am a total nutcase, I also own a bike with a 250watt hub motor. It cost me three times as much, at least, it has less power and is less fun. No one can tell that it is a motorized bike. A lot of the fun for me is the "Look what I can do" factor.

08-07-2009, 03:12 AM
Today I took apart the last of the pat bikes. I had a lot of fun with them and they did everything I asked them to do, but there were not the kind of bike a DIY novice could put together. So I have move back to friction drive. This time it seems to be working somewhat.

08-07-2009, 06:30 AM
Who gives up an electric bike for a tire shredder?:p Nice build, though.

08-14-2009, 12:40 AM
ah Well I like friction drive. The latest of the incarnations uses a scooter wheel on top of the rear bike wheel. No shredding at all. It does however have a bit of an ugly problem. But there form follows function.http://i30.tinypic.com/wi0j1l.jpg

since the picture I have changed the tires and wheels.

08-14-2009, 01:04 AM
Hmm, a scooter wheel atop the rear wheel. That's not a bad idea, although I'd personally put it on the front wheel. It looks very dangerous (to me) where its located now, because of its proximity to the rider. Great idea, though. That way you don't go through tires every hundred/few hundred miles, like with the majority of friction drives. On a different note, I'm willing to bet you could easily go into business selling PAT's just like the one in the OP, if you ever had the notion.

08-14-2009, 01:04 PM
It had occurred to me once upon a time, but I'm not physically up to the task of opening another business. The best I can do is give the details to anyone else who might want to do that.

On the front wheel thing, I tried it but the bike was very unstable. I just make sure I don't lean back too far. Actually I have never had an incident on one like this. You could also move the drive wheel farther back as well. There is no reason it has to be that close to the seat.

When I started with the PAT... It was with a scooter wheel and a couple of rails. It was very slow. When I finished I have moved everything to a 16" kids bike and running a smaller sprocket on the 16" wheel and it would run so fast even on hills that I could not catch up to pedal even in a high gear.

This particular friction drive, I am still working the bugs out of. In the 350watt version on that bike, it does not need a controller just a simple household on off switch. However in the 500 watt version it burned out the switch. Those switches are the only weak spot in the system. I am in contact with a gentleman on a different forum who is using a relay and switch. That seems to be the way I go next. Get a couple, one for each bike, and stop worrying about the switch melt down.

I do not like controllers and throttles. It's not like I run a bike on anything except wide open anyway. They just don't have that much power. You don't really need a low speed, just shut the motor off and pedal.

I have another wheel on a fed ex truck somewhere. When it gets here I am going to measure the sprocket to see if there is a smaller one somewhere. I also have on a ups truck somewhere a larger sprocket for the scooter motor.

As of this moment the 350 watt motor is the one that is my workhorse bike. I will be building the 500watt in the next few days and from that I will know what I need to do to make a hummer bike, if it is possible.

08-14-2009, 03:48 PM
Too bad, I'm willing to bet you wouldn't have any problems selling them. Most people don't want to ride a 16" bike, but would love to have a single wheeled pusher for their 26" mountain bike, I can almost guarantee you. Speaking of larger wheels, have you considered putting this 16" rear wheel on a 20" frame and 20" front wheel? I've seen it done before, and it didn't look as silly as it might sound, and seems to me like it would be much more comfortable for an adult.

Can you tell give us some of the performance characteristics of both of these bikes? I realize exact speeds can be hard to obtain without a portable GPS, but how about distance for both the PAT and this current friction drive bike? What size batteries did you use, in Ah? Can you give us an estimate of the build time for either/both of these bikes? Oh yeah, where in the world do you have the batteries hidden on this latest one? Whew, that's a lot of questions!:o

08-14-2009, 07:58 PM
I didn't have the battery trailer connected for the batteries on the lastest one.

The 16" Pat is far superior to any friction I have built yet but I'm just starting a new round of tests. The Pat with the 16" wheel and 44 tooth #25 sprocket welded to the regular sprocket, powered by the 500 watt scooter motor seemed to be almost too fast for me to be comfortable with. I never felt good about going full throttle down even the slightest incline. I also never found a normal hill that I could catch up the pedals with the motor even going uphill on any of the hill around my town. I live in a place called high point.

The 350 watt pusher was about equivalent to a 25cc weed eater friction drive I used to build. I would pull you up most hills without any help, but to keep the speed up I pedaled on most of them.

The only friction I have built successfully is the 350 watt. It has some things about it I like a lot. Much better battery economy for one thing. It goes much slower so you expect it to be slow. I use the on off switch to pump up the speed then just let it coast. Then pump it up again when the speeds to what is about normal for a bike.

I use two sets of sla batteries one is 7.5 ah and one is 12ah. I had thought I might combine them for a longer ride but haven't found anywhere I want to go just yet.

It is a two mile ride to the park were I take my morning walk. I take the 350watt friction drive bike these days. I leave with each battery in the pack at about 13.25 volts. After the two mile ride the 7.5 ah pack usually is at 12.9 - 12.7 volts on return to the shop. Since the motor is about useless at less than 12 volts I figure it would do about 4 to 5 miles with the 7.5 ah pack. Probably 7or so with the 12ah pack.

The pat was far superior in performance but handling wasn't as good as the friction drive.

Now that I know how to do it, if I had the parts on hand, I could build one in a day easily. Once you cut your side rails from some solid steel channel, like the bed frame looking stuff, it is a breeze. I had to rig some metal pieces to be able to attach them to the bike frame. The 16" wheel just bolts through a couple of 3/8" holes you drill into the bed frame material. Bolt or weld a couple of end pieces to make it ridged and you are pretty much finished with the frame.

I used a motor mount from a schwinn type scooter but you could build your own easily and probably get a better one in the process. Then just wire it up and off you go. They are really easy to build after you figure them out.

08-14-2009, 09:05 PM
I wanted to test my trailer since I did some changes, so I rode the 350watt bike that I use for my trips to and from the part for my morning walk. I know I said that already. I ran the test track two miles under various condition. A couple of short but steep hills, a couple of mild inclines and the ups and downs they cause gives the bike and trailer a good test.

I had a little more tension to start than I usually have so the bike hummed. I left it right from the charger which should be about 13.25 no more than that for sure. I came home with the battery at 12.78 So I estimate useful distance on the 7.5 ah pack at 4 to 5 miles.

I think this one might be the ideal helper motor. I want to try the 500 watt before I declare the 350 winner but it is going to be hard to beat. As a motorized bike the 500 watt might be better in that it will keep the power up longer on the hills, I think. But purely as a helper motor the 350 is nice. In the two miles I rode I was on the pedals no more than fifty yards.

Part of the reason I pedal so little with the 350 is that it has the kiddie chain ring. It is impossible to catch the freewheel, unless the bike is dragging. One day I might check to see if I have a larger chainring around. My new motor won't get here till Tuesday, I should be really bored by then.

08-15-2009, 04:59 AM
Part of the reason I pedal so little with the 350 is that it has the kiddie chain ring. It is impossible to catch the freewheel, unless the bike is dragging.

Oh, I totally forgot about that. Yeah, you'd have to be pedaling at about 500 RPM to keep up, wouldn't you?:D We'd smell your pants burning before you got close enough to see!

Do you think if I were to build a PAT with a 350 watt motor on a 16" wheel that I'd be able to use a single throw switch, 0V or 24V, all or nothing? Would that work, or would I just be building myself a tire melter?

BTW, have you ever done a 49cc PAT? If not, do you think it would work? I would love to do some experimentation with some single wheeled PAT's, both electric and ICE. Thanks for showing us how you built these, and taking the time to explain everything so those of us with no experience can learn through you.

08-15-2009, 12:46 PM
Well about the best I can do is give you a head start. Each bike is a little different and needs a little bit different attachment. If you think of it as an extension to the frame, you are on the right track. The more rigid the better.

350 on a 16 inch Pat wheel should be find for a start and go. Pedal a few times to break the inertia and kick the motor in. It won't give you any problems at all. You really need the controller on bigger motors because the start up is so violent on the chain drive. Most (but not all) of my chain problems were from the motor not being mounted rigid enough. It tends to torque on me.

I never built a fume spewer pat, but I think it would work just fine. You could even use the centrifugal clutch without any problem. I think even a 31cc weed eater would make a good assist engine. A chainsaw would be great. You would just need to weld a bike sprocket (easy enough to buy one from tnc) to the sprocket already on one of those.

There should be lots of ways to power a pat.

07-30-2012, 01:45 PM
Good innovation.you have proved that necessity is the mother of invention.