Fat Tire Granny Bike?

[gustavh]

Hello playa bike builders!

Has anyone used the granny bike quad kit (http://www.thegrannybike.com/index.html) on fat tire bikes, ie the Mongoose Beast? I'd really like to build a quadricycle this year and I think the granny bike is the easiest way to go, I'm just not sure if it will work with the beast.

On the granny bike website he states that "The bicycle must have a triangular opening at the top of the rear fork under the riders seat. This is the attachment point and provides the lateral support of the conversion kit. The conversion kit is not compatible with specialty frames. e.g. frames with long seat posts that has the triangular opening too low at the end of the rear fork. This does not allow enough clearance for the feet to clear the cross support when peddling." Here's a pic of the granny bike rear support:

gb_blueboxholder.JPG

The attachment point on the beast is much lower than the recommended "under the seat". I'm having trouble uploading another pic, but here's a link with pics and dimensions of the beast http://ratrodbikes.com/forum/index.php? ... ers.70721/. I'm also concerned that the rear fork on the beast is much wider than a standard bike.

What do you guys think? Will it work or should we go a different direction? Thanks!

[FIGJAM]

I would just get a length of pipe, put a T of pipe on each end, and sleeve that on to the seat posts.

Then you could put the angle brackets anywhere you want.

[gustavh]

Genius, Figjam thank you!!

[EspressoDude]

OR, a U-bolt in place of the existing bolt. just drill one more hole

[gustavh]

Thanks EspressoDude!

Ok so we got the bikes and the kit. I'm chugging along putting it together. It turns out that my initial concern will not be a problem, the back piece will just be angled. However, I am scratching my head about something:

In all of the pictures I've seen of the kit online, there is a bar that connects the two bikes at the top of the front fork, like this:


The instructions for the kit that we received (and the parts) say to connect the two bikes on the inside of the two front forks, ~6 inches up with a thick aluminum strap....so I'm thinking it's going to make turning impossible....Is there any way that the instructions could be correct? I think we can modify it to make it like the above image, I'm just wondering if I'm overlooking something.

[Ano]

I got one of these kits last year, and it ended up being a regretful experience. Your mileage may vary, however..

Yeah, I skipped the part where it told me to bolt both the forks together. I'm not sure what was intended with that, but it appeared to make turning impossible.

[giantlady88]

Hi,
We built a Fat Tire Trike using 2 Mongoose Beasts, but it is more complicated than a kit. We are wondering if we should make them to sell to burners, or just post some plans online. Let me know what you think!
http://threefeetofair.wordpress.com/201 ... on-a-ride/

https://www.facebook.com/photo.php?fbid ... =3&theater

[gustavh]

Ano, I'm starting to regret this purchase as well...

giantlady, love that trike!! Before deciding on the granny bike, I searched for any side-by-side mods of a mongoose beast but couldn't find anything. I think people would be very interested to see instructions posted online and those who don't have the skills may be interested in buying. Good luck!

[Ano]

If you have some specific questions, I might be able to help. What part of the thing, specifically, is troubling you?

Also, when you set it up to ride on playa, MAKE SURE the bikes are totally straight and even... otherwise you're gonna have a very tough ride! Also, I braced mine with some extra PVC to make sure they wouldn't bow in on each other.

edit: Of course, like any good Burner, I took exactly zero pictures of the completed monstrosity. SORRY! I failed.

[gustavh]

Thanks Ano! We're still working on the bike, and so far we've made lots of modifications. I'll post a picture soon and hopefully some of you can weigh in on the mods...

Do you have any tips for making sure the bikes are level while setting up on the playa? Did you use a square and a level?

[tahiti_treat]

I"m afraid I have nothing to contribute to the conversation but I just had to tell you how utterly adorable the doggie in your avatar is.

[Ano]

Trial and error, and tons of it. We set up the bikes inbetween some concrete blocks to stay straight, and then got it as straight as we could, tightened and attached, rode it for a minute, and then did it again and again until we got it as best as we could. It was a painful experience, and probably a large part of the reason (amongst others) why it was such a dud for us. We did have nice flat playa in camp, but... still. Tough.

[gustavh]

I"m afraid I have nothing to contribute to the conversation but I just had to tell you how utterly adorable the doggie in your avatar is.

Thank you! That's gustavh, aka Gus. He's a sweetheart

Trial and error, and tons of it. We set up the bikes inbetween some concrete blocks to stay straight, and then got it as straight as we could, tightened and attached, rode it for a minute, and then did it again and again until we got it as best as we could. It was a painful experience, and probably a large part of the reason (amongst others) why it was such a dud for us. We did have nice flat playa in camp, but... still. Tough.

I'm starting to get freaked out that this isn't going to work. I keep having images of us somewhere in deep playa in the middle of the night with 2 huge bikes that have collapsed in on themselves!

We went with Figjam's suggestion of a length of pipe and 2 Ts sleeved over the seat post in the rear, and we improvised a reinforced PVC section in the front rather than following the instructions provided with the kit, which was to bolt the front forks together. The problem is that we can't figure out how to get the bikes stable enough, and they really want to collapse in on each other. There is a lot of wiggle room in both the front and rear connections. We need some sort of lateral bracing that is attached to the frame, I think, in order for it to work. I'll post pictures this evening.

Over the last few days I've started thinking it would just be easier to convert them into a trike. The problem is, neither of us know how to weld, and time is running short! We do have friends and family may be able to help with the welding aspect though. So my question is, how difficult would it be for a novice to hack 2 frames into a side-by-side trike? Is it doable?

[Ano]

Hooray! It turns out I do, in fact, have some pictures of my set-up that might be able to help you.

First off - Relax! If all else fails, you have two functional bikes. I actually ended up in the sameheadspace as you, and I'm actually learning how to weld with the sole purpose of bringing a two-seat tricycle to BM 2015 or 2016! I have a hard time telling the difference between a hammer and my foot. You can do this! If you've managed to get them together without help, you're better than I am. I had to call in help to just get them together the first time.

Secondly - I did do extra bracing in order to prevent the bikes from bowing in on each other. When assembled, does one bike start to sort of "hop" towards the other one, bowing inwards (sort of like this: from |-| to \-| : If one bike is the "\" and the other is the "|")? I had one extra PVC brace on the front, and one extra PVC brace on the back. This prevented that problem, however, they were still difficult to ride.

Third - finish it! You'll regret not taking it out on at least one spin. Not gonna lie, one of my favorite moments of BM 2013 was sitting in the middle of the open playa with our janky shitmobile of a quad. WE built it, WE put it together, and then WE took it apart and rode it as two separate bikes for the rest of the week because it was easier... but for one night, we were the king and queen of the playa, riding our janky shitmobile quad

Hope the next few pictures help. YOU CAN DO THIS!

first.jpg

These are the bikes before adding any extra bracing to them. Not pictured is my utter and complete frustration at getting this far before realizing we still had a bit more to go. You can see one of the braces here, near the front. The other one was near the back, attached near the rear frame-thing. And I totally don't have a picture of it. I'm sorry.

10555137_10152638082564343_313485378_n.jpg

Front shot of the bikes. Turns out I remembered slightly wrong - we did two extra PVC bracing. Attached with a hose-clampish type thing (SORRY! IM SO NOT TECHNICAL AND I DONT REMEMBER THE NAMES!) and a screw. Each PVC brace is two pieces of PVC attached in the center with an elbow of sorts, to allow a bit of flexing if needed.

10559293_10152638082569343_1362048786_n.jpg

Closeup shot one. Not sure if helpful? This was before adding the second brace.

Had to find my old phone to dig these pictures up... anyway:

YOU CAN DO IT! Half the fun of this whole thing is the learning process! When I started going to Burning Man, I had never used a power tool in my life, had never heard of a deep-cycle battery, and had never dreamed of building anything. Now I have a functional solar set-up with a FIGJAM bucket cooler, I'm learning to weld to eventually build my own playa trike, I've done a bunch of basic bike maintenance, and learned so much more. YOU CAN DO IT!

[gustavh]

Ano! Thank you so much for posting those, they really do help. Also, I love your bikes!

On that note, I totally intended to post pictures last night but instead I had a full-blown project freak out and was nearly ready to scrap the granny bike and chop up the bikes to make a trike. This was followed by an evening of research and more stress on the possibility of making a 2 person trike. Then I came to my senses as I realized it's not going to happen (at least not this year!).

So it's back to trying to make this stupid thing work. The problem is that it is completely unstable. In the front we have a PVC bar, reinforced with a wood dowel, that is bolted to the two frames with a u bolt. I shaved off part of the PCV where it makes contact with the frame so that it will lay flat, but there is still a lot of wiggle room in this connection. In the rear, where the T is sleeved over the seat post, there is a lot of wiggle room because the diameter of the PVC is wider than that of the seat post. We also have only dry-fit the PVC couplings, so there is some twisting at that joint. All of this together means that the bikes can't even stand up on their own. Using your diagram, sometimes they're like this /-/ or this \-\ or \-I or I-/.

I'm going to try installing some lateral bracing in both the front and the back, which connects the PVC to the frame at a different location. Hopefully that will help stabilize everything a bit. If anyone has any other suggestions, I'd love to hear them! My other main concern is that this thing is going to be a bitch to pedal on the playa. The bikes weigh 46lbs each and they're both single speeds. But I don't know if there's anything to be done about that!

[Bless]

I'm considering a Mongoose "Brutus" fat tire bike for this year's burn. No connectors, just solo. Any reviews, comments, or insights?



Much appreciated.

[VultureChow]

Graidawg has the dozer. Similar design. Takes a bit getting used to without hand brakes.

[Canoe]

I'm considering a Mongoose "Brutus" fat tire bike for this year's burn. No connectors, just solo. Any reviews, comments, or insights? [/img]
Much appreciated.

It's large size makes it awkward to mount without hand-brakes too.

Hard to pedal:
- need a smaller front gear or a larger rear gear (chain length)
- large roll resistance due to super heavy tire and tube (but, robust against flats, and there's a 5 mph limit)
- better tires (almost any fat bike tires is an upgrade) and downhill tubes make for a much easy roll resistance, but added cost for a BM bike

Usual issues with department store bikes. You'll to check and grease everything. Really.
And the fork may be bent.

More here
viewtopic.php?f=286&t=39589&start=150
and
viewtopic.php?f=286&t=64688#p945474
And more around if you search.

I have the version first released, Beast, and a Dolomite.

MTBR (mountain bike review) has lots on this bike under "Mongoose Beast modifications"
There's also info over on RatRodBikes and UnderGroundVelo.

[maladroit]

I have two Beasts that I haven't modified other than chopper handlebars and comfier seats. With proper greasing and bearing pressure, they have been unstoppable on deep playa drifts and ruts even with the stock gears. The only time they've become laborious to pedal is into a stiff headwind during a dust storm.

[Canoe]

My bad.
I've been dealing with dozens of people who've followed in my footsteps and bought Beasts or Dolos. But for riding in the default world.

With the flat playa and the 5mph limit, stock may be O.K. for some. I'd still want a larger gear in the rear. The brakes are a pain, and you have to remember to use the coaster brake when it's needed.
And Elliot's standard advice of BMX/chopper handle bars for comfort certainly do apply, but the stock bars aren't too bad.

[maladroit]

And Elliot's standard advice of BMX/chopper handle bars for comfort certainly do apply, but the stock bars aren't too bad.

I am tall and have the seat up really high. The stock straight mountain bar meant a lot of uncomfortable hunching forward, rather than sitting back and enjoying the scenery on a slow ride down Esplanade.

[Canoe]

Yup.
Frame comes in one size.
Many larger folk the larger bars aren't enough, and they have to resort to a setback seat tube too.
I'm planning on going to a "loaf" seat. Held up at the rear with an inverted Al crutch. Going to try leaving the footpad on the end.

[maladroit]

A banana seat on a fat bike? That would be cool as hell. Checking Brazilian River website....

[Canoe]

They're putting bananas with long seat posts with ape hangers on the 20" rimmed Mongoose Massif. For adults. Well, technically they're old enough to be adults.

[Bless]

Thanks for the comments, y'all. I'm going with the Mongoose, a wide comfy seat, and a larger rear cog. To switch out the rear cog, do I need a longer chain?

I don't think I'm ready for the chopper handlebars yet.

[Tiahaar]

I've put 21t on the rear of Beasts and kept same chain length, nice ratio for playa...22t requires adding a link pair to the chain.

[gaminwench]

add a stuffed furry to your seat.
Thank me later.

[Elliot]

Beast with cruiser saddle and BMX handlebar.
And I can confirm that a 22-tooth rear sprocket requires one link (two pins) longer chain. Same with Huffy Cranbrook and similar bikes.

[Bless]

Thanks again, everyone. How do I figure out what size links are compatible with the stock chain included with the Mongoose? 1/8 inch?

[Elliot]

Yes, bikes with no gears (or one gear, depending on how you think of it), and bikes with gears built into the wheel-hub, use 1/8 chain.
Bikes with derailer gearing use the narrower 3/32 chain.